diff --git a/audio/engine.asm b/audio/engine.asm
index 067e4ff87..1aac5aa41 100644
--- a/audio/engine.asm
+++ b/audio/engine.asm
@@ -408,7 +408,7 @@ UpdateChannels: ; e8125
 	ret
 
 .asm_e824d
-	ld a, $3f
+	ld a, $3f ; sound length
 	ld [rNR31], a
 	xor a
 	ld [rNR30], a
@@ -1304,8 +1304,8 @@ ParseSFXOrRest: ; e8698
 	ld [hl], a
 	; are we on the last channel? (noise sampling)
 	ld a, [CurChannel]
-	and $3
-	cp $3
+	maskbits NUM_MUSIC_CHANS +- 1
+	cp CHAN4
 	ret z
 	; update hi frequency from next param
 	call GetMusicByte
@@ -1320,8 +1320,8 @@ GetNoiseSample: ; e86c5
 ; load ptr to sample header in NoiseSampleAddress
 	; are we on the last channel?
 	ld a, [CurChannel]
-	and $3
-	cp $3
+	and NUM_MUSIC_CHANS +- 1
+	cp CHAN4
 	; ret if not
 	ret nz
 	; update note duration
@@ -1668,7 +1668,7 @@ MusicEE; e883e
 ; if ????, jump
 	; get channel
 	ld a, [CurChannel]
-	and $3 ; ch0-3
+	maskbits NUM_MUSIC_CHANS +- 1
 	ld e, a
 	ld d, 0
 	; hl = Channel1JumpCondition + channel id
@@ -1966,8 +1966,8 @@ Music_NoteType: ; e8963
 	add hl, bc
 	ld [hl], a
 	ld a, [CurChannel]
-	and $3
-	cp CHAN8 & $3
+	maskbits NUM_MUSIC_CHANS +- 1
+	cp CHAN4
 	ret z
 	; intensity
 	call Music_Intensity
@@ -2414,7 +2414,7 @@ SetLRTracks: ; e8b1b
 	push de
 	; store current channel in de
 	ld a, [CurChannel]
-	and $3
+	maskbits NUM_MUSIC_CHANS +- 1
 	ld e, a
 	ld d, 0
 	; get this channel's lr tracks
@@ -2449,7 +2449,7 @@ _PlayMusic:: ; e8b30
 	call LoadMusicByte ; store first byte of music header in a
 	rlca
 	rlca
-	and $3 ; get number of channels
+	maskbits NUM_MUSIC_CHANS +- 1
 	inc a
 .loop
 ; start playing channels
@@ -2505,7 +2505,7 @@ _PlayCryHeader:: ; e8b79
 	; Top 2 bits contain the number of channels
 	rlca
 	rlca
-	and 3
+	maskbits NUM_MUSIC_CHANS +- 1
 
 ; For each channel:
 	inc a
@@ -2530,8 +2530,8 @@ _PlayCryHeader:: ; e8b79
 
 ; No tempo for channel 4
 	ld a, [CurChannel]
-	and 3
-	cp 3
+	maskbits NUM_MUSIC_CHANS +- 1
+	cp CHAN4
 	jr nc, .start
 
 ; Tempo is effectively length
@@ -2669,7 +2669,7 @@ _PlaySFX:: ; e8c04
 	call LoadMusicByte
 	rlca ; top 2
 	rlca ; bits
-	and $3
+	maskbits NUM_MUSIC_CHANS +- 1
 	inc a ; # channels -> # loops
 .startchannels
 	push af
@@ -2722,7 +2722,7 @@ PlayStereoSFX:: ; e8ca6
 	call LoadMusicByte
 	rlca
 	rlca
-	and 3 ; ch1-4
+	maskbits NUM_MUSIC_CHANS +- 1
 	inc a
 
 .loop
@@ -2736,7 +2736,7 @@ PlayStereoSFX:: ; e8ca6
 	push de
 	; get tracks for this channel
 	ld a, [CurChannel]
-	and 3 ; ch1-4
+	maskbits NUM_MUSIC_CHANS +- 1
 	ld e, a
 	ld d, 0
 	call GetLRTracks
diff --git a/constants/item_data_constants.asm b/constants/item_data_constants.asm
index 2e7c2eb2e..9b80c7b50 100644
--- a/constants/item_data_constants.asm
+++ b/constants/item_data_constants.asm
@@ -9,21 +9,15 @@
 	const ITEMATTR_HELP
 ITEMATTR_STRUCT_LENGTH EQU const_value
 
-
-; pack pockets
-ITEM     EQU 1
-KEY_ITEM EQU 2
-BALL     EQU 3
-TM_HM    EQU 4
-
-; pack pocket sizes
-MAX_ITEMS     EQU 20
-MAX_KEY_ITEMS EQU 25
-MAX_BALLS     EQU 12
-MAX_PC_ITEMS  EQU 50
-
+; item types
+const_value set 1
+	const ITEM     ; 1
+	const KEY_ITEM ; 2
+	const BALL     ; 3
+	const TM_HM    ; 4
 
 ; item menu types
+; UseItem.dw indexes (see engine/pack.asm)
 ITEMMENU_NOUSE   EQU 0
 ITEMMENU_CURRENT EQU 4
 ITEMMENU_PARTY   EQU 5
@@ -34,6 +28,20 @@ CANT_SELECT EQU 1 << 6
 CANT_TOSS   EQU 1 << 7
 
 
+; pack pockets
+	const_def
+	const ITEM_POCKET     ; 0
+	const BALL_POCKET     ; 1
+	const KEY_ITEM_POCKET ; 2
+	const TM_HM_POCKET    ; 3
+NUM_POCKETS EQU const_value +- 1
+
+MAX_ITEMS     EQU 20
+MAX_BALLS     EQU 12
+MAX_KEY_ITEMS EQU 25
+MAX_PC_ITEMS  EQU 50
+
+
 ; mail
 MAIL_MSG_LENGTH    EQU $20
 MAILBOX_CAPACITY   EQU 10
diff --git a/constants/landmark_constants.asm b/constants/landmark_constants.asm
index 4a15928f0..4de94ddf9 100644
--- a/constants/landmark_constants.asm
+++ b/constants/landmark_constants.asm
@@ -100,3 +100,13 @@ KANTO_LANDMARK EQU const_value
 	const TOHJO_FALLS       ; 5d
 	const ROUTE_28          ; 5e
 	const FAST_SHIP         ; 5f
+
+; used in CaughtData
+GIFT_LOCATION  EQU $7e
+EVENT_LOCATION EQU $7f
+
+
+; Regions
+	const_def
+	const JOHTO_REGION ; 0
+	const KANTO_REGION ; 1
diff --git a/constants/misc_constants.asm b/constants/misc_constants.asm
index 3917ff8f5..14c6b313f 100644
--- a/constants/misc_constants.asm
+++ b/constants/misc_constants.asm
@@ -86,3 +86,10 @@ const_value = 1
 
 ; day-care
 MAX_DAY_CARE_EXP EQU $500000
+
+; bug-catching contest
+BUG_CONTEST_MINUTES EQU 20
+BUG_CONTEST_SECONDS EQU 0
+BUG_CONTEST_PLAYER EQU 1
+NUM_BUG_CONTESTANTS EQU 10 ; not counting the player
+BUG_CONTESTANT_SIZE EQU 4
diff --git a/constants/music_constants.asm b/constants/music_constants.asm
index 453bf9098..e0d3dcaa3 100644
--- a/constants/music_constants.asm
+++ b/constants/music_constants.asm
@@ -111,6 +111,10 @@
 ; GetMapHeaderMusic picks music for this value (see home/map.asm)
 MUSIC_MAHOGANY_MART EQU $64
 
+; ExitPokegearRadio_HandleMusic uses these values
+RESTART_MAP_MUSIC EQU $fe
+ENTER_MAP_MUSIC   EQU $ff
+
 ; GetMapHeaderMusic picks music for this bit flag
 RADIO_TOWER_MUSIC_F EQU 7
 RADIO_TOWER_MUSIC EQU 1 << RADIO_TOWER_MUSIC_F
diff --git a/constants/npctrade_constants.asm b/constants/npctrade_constants.asm
index 2da4abd64..5464e4dbb 100644
--- a/constants/npctrade_constants.asm
+++ b/constants/npctrade_constants.asm
@@ -19,3 +19,25 @@ TRADE_PADDING EQU 31
 	const NPCTRADE_CHRIS  ; 4
 	const NPCTRADE_KIM    ; 5
 	const NPCTRADE_FOREST ; 6
+
+; trade gender limits
+TRADE_EITHER_GENDER EQU 0
+TRADE_MALE_ONLY     EQU 1
+TRADE_FEMALE_ONLY   EQU 2
+
+; TradeTexts indexes (see engine/npctrade.asm)
+
+; trade dialogs
+	const_def
+	const TRADE_INTRO
+	const TRADE_CANCEL
+	const TRADE_WRONG
+	const TRADE_COMPLETE
+	const TRADE_AFTER
+
+; trade dialog sets
+	const_def
+	const TRADE_DIALOG_COLLECTOR
+	const TRADE_DIALOG_HAPPY
+	const TRADE_DIALOG_NEWBIE
+	const TRADE_DIALOG_GIRL
diff --git a/constants/pokemon_data_constants.asm b/constants/pokemon_data_constants.asm
index a489da39c..65dd35fd0 100644
--- a/constants/pokemon_data_constants.asm
+++ b/constants/pokemon_data_constants.asm
@@ -63,6 +63,10 @@ const_value set 1
 	const NO_EGGS      ; f
 
 
+; pokedex entries (see data/pokemon/dex_entries.asm)
+NUM_DEX_ENTRY_BANKS EQU 4
+
+
 ; party_struct members (see macros/wram.asm)
 MON_SPECIES            EQUS "(PartyMon1Species - PartyMon1)"
 MON_ITEM               EQUS "(PartyMon1Item - PartyMon1)"
@@ -98,6 +102,21 @@ PARTYMON_STRUCT_LENGTH EQUS "(PartyMon1StatsEnd - PartyMon1)"
 REDMON_STRUCT_LENGTH EQU 44
 
 
+; caught data
+
+CAUGHT_TIME_MASK  EQU %11000000
+CAUGHT_LEVEL_MASK EQU %00111111
+
+CAUGHT_GENDER_MASK   EQU %10000000
+CAUGHT_LOCATION_MASK EQU %01111111
+
+CAUGHT_BY_UNKNOWN EQU 0
+CAUGHT_BY_GIRL    EQU 1
+CAUGHT_BY_BOY     EQU 2
+
+CAUGHT_EGG_LEVEL EQU 1
+
+
 ; maximum number of party pokemon
 PARTY_LENGTH EQU 6
 
diff --git a/constants/wram_constants.asm b/constants/wram_constants.asm
index f2cdf7039..755c89bdc 100644
--- a/constants/wram_constants.asm
+++ b/constants/wram_constants.asm
@@ -52,6 +52,7 @@ const_value set -1
 	const UP       ; 1
 	const LEFT     ; 2
 	const RIGHT    ; 3
+NUM_DIRECTIONS EQU const_value
 
 DOWN_MASK  EQU 1 << DOWN
 UP_MASK    EQU 1 << UP
@@ -71,6 +72,7 @@ FACE_RIGHT EQU 1
 	const DAY_F      ; 1
 	const NITE_F     ; 2
 	const DARKNESS_F ; 3
+NUM_DAYTIMES EQU const_value
 
 MORN     EQU 1 << MORN_F
 DAY      EQU 1 << DAY_F
diff --git a/data/bug_contest_flags.asm b/data/bug_contest_flags.asm
new file mode 100644
index 000000000..04d748270
--- /dev/null
+++ b/data/bug_contest_flags.asm
@@ -0,0 +1,13 @@
+BugCatchingContestantEventFlagTable: ; 139fe
+; there are NUM_BUG_CONTESTANTS entries
+	dw EVENT_BUG_CATCHING_CONTESTANT_1A
+	dw EVENT_BUG_CATCHING_CONTESTANT_2A
+	dw EVENT_BUG_CATCHING_CONTESTANT_3A
+	dw EVENT_BUG_CATCHING_CONTESTANT_4A
+	dw EVENT_BUG_CATCHING_CONTESTANT_5A
+	dw EVENT_BUG_CATCHING_CONTESTANT_6A
+	dw EVENT_BUG_CATCHING_CONTESTANT_7A
+	dw EVENT_BUG_CATCHING_CONTESTANT_8A
+	dw EVENT_BUG_CATCHING_CONTESTANT_9A
+	dw EVENT_BUG_CATCHING_CONTESTANT_10A
+; 13a12
diff --git a/data/bug_contest_winners.asm b/data/bug_contest_winners.asm
index 8529ed0f0..7a465edf5 100644
--- a/data/bug_contest_winners.asm
+++ b/data/bug_contest_winners.asm
@@ -1,5 +1,6 @@
 BugContestantPointers: ; 13783
-	dw BugContestant_BugCatcherDon ; This reverts back to the player
+; there are NUM_BUG_CONTESTANTS + 1 entries
+	dw BugContestant_BugCatcherDon ; this reverts back to the player
 	dw BugContestant_BugCatcherDon
 	dw BugContestant_BugCatcherEd
 	dw BugContestant_CooltrainerMNick
@@ -12,6 +13,12 @@ BugContestantPointers: ; 13783
 	dw BugContestant_SchoolboyKipp
 ; 13799
 
+; contestant format:
+;   db class, id
+;   dbw 1st-place mon, score
+;   dbw 2nd-place mon, score
+;   dbw 3rd-place mon, score
+
 BugContestant_BugCatcherDon:
 	db BUG_CATCHER, DON
 	dbw KAKUNA,     300
diff --git a/data/npc_trades.asm b/data/npc_trades.asm
index 57b2411d3..d16670984 100644
--- a/data/npc_trades.asm
+++ b/data/npc_trades.asm
@@ -1,7 +1,3 @@
-TRADE_EITHER_GENDER EQU 0
-TRADE_MALE_ONLY     EQU 1
-TRADE_FEMALE_ONLY   EQU 2
-
 npctrade: MACRO
 ; dialog set, requested mon, offered mon, nickname, dvs, item, OT ID, OT name, gender requested
 	db \1, \2, \3, \4, \5, \6, \7
@@ -12,11 +8,11 @@ ENDM
 
 NPCTrades: ; fce58
 ; entries correspond to NPCTRADE_* constants
-	npctrade 0, ABRA,       MACHOP,     "MUSCLE@@@@@", $37, $66, GOLD_BERRY,   37460, "MIKE@@@@@@@", TRADE_EITHER_GENDER
-	npctrade 0, BELLSPROUT, ONIX,       "ROCKY@@@@@@", $96, $66, BITTER_BERRY, 48926, "KYLE@@@@@@@", TRADE_EITHER_GENDER
-	npctrade 1, KRABBY,     VOLTORB,    "VOLTY@@@@@@", $98, $88, PRZCUREBERRY, 29189, "TIM@@@@@@@@", TRADE_EITHER_GENDER
-	npctrade 3, DRAGONAIR,  DODRIO,     "DORIS@@@@@@", $77, $66, SMOKE_BALL,   00283, "EMY@@@@@@@@", TRADE_FEMALE_ONLY
-	npctrade 2, HAUNTER,    XATU,       "PAUL@@@@@@@", $96, $86, MYSTERYBERRY, 15616, "CHRIS@@@@@@", TRADE_EITHER_GENDER
-	npctrade 3, CHANSEY,    AERODACTYL, "AEROY@@@@@@", $96, $66, GOLD_BERRY,   26491, "KIM@@@@@@@@", TRADE_EITHER_GENDER
-	npctrade 0, DUGTRIO,    MAGNETON,   "MAGGIE@@@@@", $96, $66, METAL_COAT,   50082, "FOREST@@@@@", TRADE_EITHER_GENDER
+	npctrade TRADE_DIALOG_COLLECTOR, ABRA,       MACHOP,     "MUSCLE@@@@@", $37, $66, GOLD_BERRY,   37460, "MIKE@@@@@@@", TRADE_EITHER_GENDER
+	npctrade TRADE_DIALOG_COLLECTOR, BELLSPROUT, ONIX,       "ROCKY@@@@@@", $96, $66, BITTER_BERRY, 48926, "KYLE@@@@@@@", TRADE_EITHER_GENDER
+	npctrade TRADE_DIALOG_HAPPY,     KRABBY,     VOLTORB,    "VOLTY@@@@@@", $98, $88, PRZCUREBERRY, 29189, "TIM@@@@@@@@", TRADE_EITHER_GENDER
+	npctrade TRADE_DIALOG_GIRL,      DRAGONAIR,  DODRIO,     "DORIS@@@@@@", $77, $66, SMOKE_BALL,   00283, "EMY@@@@@@@@", TRADE_FEMALE_ONLY
+	npctrade TRADE_DIALOG_NEWBIE,    HAUNTER,    XATU,       "PAUL@@@@@@@", $96, $86, MYSTERYBERRY, 15616, "CHRIS@@@@@@", TRADE_EITHER_GENDER
+	npctrade TRADE_DIALOG_GIRL,      CHANSEY,    AERODACTYL, "AEROY@@@@@@", $96, $66, GOLD_BERRY,   26491, "KIM@@@@@@@@", TRADE_EITHER_GENDER
+	npctrade TRADE_DIALOG_COLLECTOR, DUGTRIO,    MAGNETON,   "MAGGIE@@@@@", $96, $66, METAL_COAT,   50082, "FOREST@@@@@", TRADE_EITHER_GENDER
 ; fcf38
diff --git a/engine/battle/ai/move.asm b/engine/battle/ai/move.asm
index 11586c0da..72ed6983b 100755
--- a/engine/battle/ai/move.asm
+++ b/engine/battle/ai/move.asm
@@ -56,7 +56,7 @@ AIChooseMove: ; 440ce
 	inc hl
 	ld a, [de]
 	inc de
-	and $3f
+	and PP_MASK
 	jr nz, .CheckMovePP
 	ld [hl], 80
 	jr .CheckMovePP
@@ -186,7 +186,7 @@ AIChooseMove: ; 440ce
 .ChooseMove:
 	ld hl, Buffer1
 	call Random
-	and 3
+	maskbits NUM_MOVES +- 1
 	ld c, a
 	ld b, 0
 	add hl, bc
diff --git a/engine/battle/battle_transition.asm b/engine/battle/battle_transition.asm
index 383674652..4c05112ac 100644
--- a/engine/battle/battle_transition.asm
+++ b/engine/battle/battle_transition.asm
@@ -640,8 +640,8 @@ StartTrainerBattle_LoadPokeBallGraphics: ; 8c5dc (23:45dc)
 .cgb
 	ld hl, .daypals
 	ld a, [TimeOfDayPal]
-	and $3
-	cp 3
+	maskbits NUM_DAYTIMES +- 1
+	cp DARKNESS_F
 	jr nz, .daytime
 	ld hl, .nightpals
 .daytime
diff --git a/engine/battle/core.asm b/engine/battle/core.asm
index 5b5b3562e..35d2098bc 100644
--- a/engine/battle/core.asm
+++ b/engine/battle/core.asm
@@ -730,7 +730,7 @@ HandleEncore: ; 3c4df
 	ld b, 0
 	add hl, bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	ret nz
 
 .end_player_encore
@@ -754,7 +754,7 @@ HandleEncore: ; 3c4df
 	ld b, 0
 	add hl, bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	ret nz
 
 .end_enemy_encore
@@ -1401,7 +1401,7 @@ HandleMysteryberry: ; 3c93c
 	and a
 	jr z, .quit
 	ld a, [de]
-	and $3f
+	and PP_MASK
 	jr z, .restore
 	inc hl
 	inc de
@@ -5650,7 +5650,7 @@ MoveSelectionScreen: ; 3e4bc
 	ld b, 0
 	add hl, bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	jr z, .no_pp_left
 	ld a, [PlayerDisableCount]
 	swap a
@@ -5849,7 +5849,7 @@ MoveInfoBox: ; 3e6c8
 	ld hl, BattleMonPP
 	add hl, bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	ld [StringBuffer1], a
 	call .PrintPP
 
@@ -5912,7 +5912,7 @@ CheckPlayerHasUsableMoves: ; 3e786
 	or [hl]
 	inc hl
 	or [hl]
-	and $3f
+	and PP_MASK
 	ret nz
 	jr .force_struggle
 
@@ -5934,8 +5934,7 @@ CheckPlayerHasUsableMoves: ; 3e786
 
 .done
 	; Bug: this will result in a move with PP Up confusing the game.
-	; Replace with "and $3f" to fix.
-	and a
+	and a ; should be "and PP_MASK"
 	ret nz
 
 .force_struggle
@@ -6014,7 +6013,7 @@ ParseEnemyAction: ; 3e7c1
 	cp [hl]
 	jr z, .disabled
 	ld a, [de]
-	and $3f
+	and PP_MASK
 	jr nz, .enough_pp
 
 .disabled
@@ -6032,7 +6031,7 @@ ParseEnemyAction: ; 3e7c1
 .loop2
 	ld hl, EnemyMonMoves
 	call BattleRandom
-	and 3 ; TODO factor in NUM_MOVES
+	maskbits NUM_MOVES +- 1
 	ld c, a
 	ld b, 0
 	add hl, bc
@@ -6049,7 +6048,7 @@ ParseEnemyAction: ; 3e7c1
 	add hl, bc
 	ld b, a
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	jr z, .loop2
 	ld a, c
 	ld [CurEnemyMoveNum], a
diff --git a/engine/battle/effect_commands.asm b/engine/battle/effect_commands.asm
index f9a8ba63e..68184ce30 100644
--- a/engine/battle/effect_commands.asm
+++ b/engine/battle/effect_commands.asm
@@ -846,19 +846,20 @@ BattleCommand_CheckObedience: ; 343db
 
 
 .DoNothing:
+	; 4 random choices
 	call BattleRandom
-	and 3
+	and %11
 
 	ld hl, LoafingAroundText
-	and a
+	and a ; 0
 	jr z, .Print
 
 	ld hl, WontObeyText
-	dec a
+	dec a ; 1
 	jr z, .Print
 
 	ld hl, TurnedAwayText
-	dec a
+	dec a ; 2
 	jr z, .Print
 
 	ld hl, IgnoredOrdersText
@@ -888,7 +889,7 @@ BattleCommand_CheckObedience: ; 343db
 
 .GetTotalPP:
 	ld a, [hli]
-	and $3f ; exclude pp up
+	and PP_MASK
 	add b
 	ld b, a
 
@@ -911,7 +912,7 @@ BattleCommand_CheckObedience: ; 343db
 
 ; Can't use another move if only one move has PP.
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	cp b
 	jr z, .DoNothing
 
@@ -931,7 +932,7 @@ BattleCommand_CheckObedience: ; 343db
 
 .RandomMove:
 	call BattleRandom
-	and 3 ; TODO NUM_MOVES
+	maskbits NUM_MOVES +- 1
 
 	cp b
 	jr nc, .RandomMove
@@ -947,7 +948,7 @@ BattleCommand_CheckObedience: ; 343db
 	ld d, 0
 	add hl, de
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	jr z, .RandomMove
 
 
@@ -1118,7 +1119,7 @@ BattleCommand_DoTurn: ; 34555
 	ld b, 0
 	add hl, bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	jr z, .out_of_pp
 	dec [hl]
 	ld b, 0
@@ -3906,7 +3907,7 @@ BattleCommand_Encore: ; 35864
 	ld bc, BattleMonPP - BattleMonMoves - 1
 	add hl, bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	jp z, .failed
 	ld a, [AttackMissed]
 	and a
@@ -4386,7 +4387,7 @@ BattleCommand_SleepTalk: ; 35b33
 .sample_move
 	push hl
 	call BattleRandom
-	and 3 ; TODO factor in NUM_MOVES
+	maskbits NUM_MOVES +- 1
 	ld c, a
 	ld b, 0
 	add hl, bc
@@ -4550,17 +4551,18 @@ BattleCommand_Spite: ; 35c0f
 	add hl, bc
 	pop bc
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	jr z, .failed
 	push bc
 	call GetMoveName
+	; lose 2-5 PP
 	call BattleRandom
-	and 3
+	and %11
 	inc a
 	inc a
 	ld b, a
 	ld a, [hl]
-	and $3f
+	and PP_MASK
 	cp b
 	jr nc, .deplete_pp
 	ld b, a
@@ -6208,13 +6210,12 @@ BattleCommand_TriStatusChance: ; 3658f
 
 	call BattleCommand_EffectChance
 
-; 1/3 chance of each status
 .loop
+	; 1/3 chance of each status
 	call BattleRandom
 	swap a
-	and 3
+	and %11
 	jr z, .loop
-; jump
 	dec a
 	ld hl, .ptrs
 	rst JumpTable
@@ -7392,7 +7393,8 @@ BattleCommand_TrapTarget: ; 36c2d
 	bit SUBSTATUS_SUBSTITUTE, a
 	ret nz
 	call BattleRandom
-	and 3
+	; trapped for 2-5 turns
+	and %11
 	inc a
 	inc a
 	inc a
@@ -7590,8 +7592,9 @@ BattleCommand_FinishConfusingTarget: ; 36d70
 
 .got_confuse_count
 	set SUBSTATUS_CONFUSED, [hl]
+	; confused for 2-5 turns
 	call BattleRandom
-	and 3
+	and %11
 	inc a
 	inc a
 	ld [bc], a
@@ -8201,7 +8204,7 @@ BattleCommand_Conversion: ; 3707f
 .done
 .loop3
 	call BattleRandom
-	and 3 ; TODO factor in NUM_MOVES
+	maskbits NUM_MOVES +- 1
 	ld c, a
 	ld b, 0
 	ld hl, StringBuffer1
diff --git a/engine/battle_anims/anim_commands.asm b/engine/battle_anims/anim_commands.asm
index b81911a88..2d5a53aa0 100644
--- a/engine/battle_anims/anim_commands.asm
+++ b/engine/battle_anims/anim_commands.asm
@@ -1207,7 +1207,7 @@ BattleAnimCmd_Sound: ; cc7cd (33:47cd)
 	srl a
 	ld [wSFXDuration], a
 	call .GetCryTrack
-	and 3
+	maskbits NUM_NOISE_CHANS +- 1
 	ld [CryTracks], a ; CryTracks
 
 	ld e, a
@@ -1244,7 +1244,7 @@ BattleAnimCmd_Sound: ; cc7cd (33:47cd)
 
 BattleAnimCmd_Cry: ; cc807 (33:4807)
 	call GetBattleAnimByte
-	and 3
+	maskbits NUM_NOISE_CHANS +- 1
 	ld e, a
 	ld d, 0
 	ld hl, .CryData
diff --git a/engine/billspc.asm b/engine/billspc.asm
index 4e4722ded..00bd49f06 100755
--- a/engine/billspc.asm
+++ b/engine/billspc.asm
@@ -136,7 +136,7 @@ _DepositPKMN: ; e2391 (38:6391)
 	jp c, BillsPCDepositFuncCancel
 	ld a, [wMenuCursorY]
 	dec a
-	and $3
+	and %11
 	ld e, a
 	ld d, 0
 	ld hl, BillsPCDepositJumptable
@@ -401,7 +401,7 @@ BillsPC_Withdraw: ; e2675 (38:6675)
 	jp c, .cancel
 	ld a, [wMenuCursorY]
 	dec a
-	and 3
+	and %11
 	ld e, a
 	ld d, 0
 	ld hl, .dw
@@ -663,7 +663,7 @@ _MovePKMNWithoutMail: ; e2759
 	jp c, .Cancel
 	ld a, [wMenuCursorY]
 	dec a
-	and 3
+	and %11
 	ld e, a
 	ld d, 0
 	ld hl, .Jumptable2
diff --git a/engine/caught_data.asm b/engine/caught_data.asm
index 1f8b8cac4..534e318a4 100644
--- a/engine/caught_data.asm
+++ b/engine/caught_data.asm
@@ -7,17 +7,17 @@ CheckPartyFullAfterContest: ; 4d9e5
 	call GetBaseData
 	ld hl, PartyCount
 	ld a, [hl]
-	cp 6
+	cp PARTY_LENGTH
 	jp nc, .TryAddToBox
 	inc a
 	ld [hl], a
 	ld c, a
-	ld b, $0
+	ld b, 0
 	add hl, bc
 	ld a, [wContestMon]
 	ld [hli], a
 	ld [CurSpecies], a
-	ld a, $ff
+	ld a, -1
 	ld [hl], a
 	ld hl, PartyMon1Species
 	ld a, [PartyCount]
@@ -75,8 +75,8 @@ CheckPartyFullAfterContest: ; 4d9e5
 	ld hl, PartyMon1CaughtLocation
 	call GetPartyLocation
 	ld a, [hl]
-	and $80
-	ld b, $13
+	and CAUGHT_GENDER_MASK
+	ld b, NATIONAL_PARK
 	or b
 	ld [hl], a
 	xor a
@@ -135,8 +135,8 @@ CheckPartyFullAfterContest: ; 4d9e5
 	call GetSRAMBank
 	ld hl, sBoxMon1CaughtLocation
 	ld a, [hl]
-	and $80
-	ld b, $13
+	and CAUGHT_GENDER_MASK
+	ld b, NATIONAL_PARK
 	or b
 	ld [hl], a
 	call CloseSRAM
@@ -227,7 +227,7 @@ SetGiftPartyMonCaughtData: ; 4dba3
 SetGiftMonCaughtData: ; 4dbaf
 	xor a
 	ld [hli], a
-	ld a, $7e
+	ld a, GIFT_LOCATION
 	rrc b
 	or b
 	ld [hl], a
@@ -239,7 +239,7 @@ SetEggMonCaughtData: ; 4dbb8 (13:5bb8)
 	call GetPartyLocation
 	ld a, [CurPartyLevel]
 	push af
-	ld a, $1
+	ld a, CAUGHT_EGG_LEVEL
 	ld [CurPartyLevel], a
 	call SetBoxmonOrEggmonCaughtData
 	pop af
diff --git a/engine/color.asm b/engine/color.asm
index 76729187a..adcb2d23d 100644
--- a/engine/color.asm
+++ b/engine/color.asm
@@ -1240,7 +1240,7 @@ LoadMapPals:
 	ld l, a
 	; Futher refine by time of day
 	ld a, [TimeOfDayPal]
-	and 3
+	maskbits NUM_DAYTIMES +- 1
 	add a
 	add a
 	add a
@@ -1286,7 +1286,7 @@ LoadMapPals:
 
 .got_pals
 	ld a, [TimeOfDayPal]
-	and 3
+	maskbits NUM_DAYTIMES +- 1
 	ld bc, 8 palettes
 	ld hl, MapObjectPals
 	call AddNTimes
@@ -1310,7 +1310,7 @@ LoadMapPals:
 	ld de, RoofPals
 	add hl, de
 	ld a, [TimeOfDayPal]
-	and 3
+	maskbits NUM_DAYTIMES +- 1
 	cp NITE_F
 	jr c, .morn_day
 rept 4
diff --git a/engine/credits.asm b/engine/credits.asm
index 5d34ba2f4..0df0d9f7b 100644
--- a/engine/credits.asm
+++ b/engine/credits.asm
@@ -504,7 +504,7 @@ GetCreditsPalette: ; 109b2c
 .GetPalAddress:
 ; Each set of palette data is 24 bytes long.
 	ld a, [wCreditsBorderMon] ; scene
-	and 3
+	and %11
 	add a
 	add a ; * 8
 	add a
@@ -549,13 +549,13 @@ Credits_LoadBorderGFX: ; 109bca (42:5bca)
 	cp $ff
 	jr z, .init
 
-	and 3
+	and %11
 	ld e, a
 	inc a
-	and 3
+	and %11
 	ld [hl], a
 	ld a, [wCreditsBorderMon]
-	and 3
+	and %11
 	add a
 	add a
 	add e
diff --git a/engine/crystal_intro.asm b/engine/crystal_intro.asm
index 84ab86113..0d86533c1 100755
--- a/engine/crystal_intro.asm
+++ b/engine/crystal_intro.asm
@@ -247,10 +247,10 @@ GameFreakLogoScene2: ; e470d (39:470d)
 	ld hl, SPRITEANIMSTRUCT_0D
 	add hl, bc
 	ld a, [hl]
-	and $3f
-	cp $20
+	and %111111
+	cp %100000
 	jr nc, .asm_e4723
-	add $20
+	add %100000
 .asm_e4723
 	ld e, a
 	farcall BattleAnim_Sine_e
@@ -1604,12 +1604,12 @@ CrystalIntro_UnownFade: ; e5223 (39:5223)
 	inc hl
 	inc hl
 	ld a, [wcf65]
-	and $3f
-	cp $1f
+	and %111111
+	cp %011111
 	jr z, .okay
 	jr c, .okay
 	ld c, a
-	ld a, $3f
+	ld a, %111111
 	sub c
 .okay
 
diff --git a/engine/events/buena.asm b/engine/events/buena.asm
index 1227593eb..3987487a9 100644
--- a/engine/events/buena.asm
+++ b/engine/events/buena.asm
@@ -17,7 +17,7 @@ SpecialBuenasPassword: ; 8af6b
 	ld a, [MenuSelection]
 	ld c, a
 	ld a, [wBuenasPassword]
-	and $3
+	maskbits NUM_PASSWORDS_PER_CATEGORY +- 1
 	cp c
 	jr nz, .wrong
 	ld b, $1
@@ -46,7 +46,7 @@ SpecialBuenasPassword: ; 8af6b
 ; 0x8afb4
 
 .PasswordIndices: ; 8afb8
-	db 3
+	db NUM_PASSWORDS_PER_CATEGORY
 	db 0, 1, 2
 	db -1
 
diff --git a/engine/events/bug_contest/contest_2.asm b/engine/events/bug_contest/contest_2.asm
index 493c69d0c..eff531c50 100755
--- a/engine/events/bug_contest/contest_2.asm
+++ b/engine/events/bug_contest/contest_2.asm
@@ -2,7 +2,7 @@ Special_SelectRandomBugContestContestants: ; 139a8
 ; Select five random people to participate in the current contest.
 
 ; First we have to make sure that any old data is cleared away.
-	ld c, 10 ; Number of people to choose from.
+	ld c, NUM_BUG_CONTESTANTS
 	ld hl, BugCatchingContestantEventFlagTable
 .loop1
 	push bc
@@ -26,9 +26,9 @@ Special_SelectRandomBugContestContestants: ; 139a8
 .next
 ; Choose a flag at uniform random to be set.
 	call Random
-	cp 250
+	cp $ff / NUM_BUG_CONTESTANTS * NUM_BUG_CONTESTANTS
 	jr nc, .next
-	ld c, 25
+	ld c, $ff / NUM_BUG_CONTESTANTS
 	call SimpleDivide
 	ld e, b
 	ld d, 0
@@ -59,7 +59,7 @@ Special_SelectRandomBugContestContestants: ; 139a8
 Special_CheckBugContestContestantFlag: ; 139ed
 ; Checks the flag of the Bug Catching Contestant whose index is loaded in a.
 
-; Bug: If a >= 10 when this is called, it will read beyond the table.
+; Bug: If a >= NUM_BUG_CONTESTANTS when this is called, it will read beyond the table.
 
 	ld hl, BugCatchingContestantEventFlagTable
 	ld e, a
@@ -74,18 +74,7 @@ Special_CheckBugContestContestantFlag: ; 139ed
 	ret
 ; 139fe
 
-BugCatchingContestantEventFlagTable: ; 139fe
-	dw EVENT_BUG_CATCHING_CONTESTANT_1A
-	dw EVENT_BUG_CATCHING_CONTESTANT_2A
-	dw EVENT_BUG_CATCHING_CONTESTANT_3A
-	dw EVENT_BUG_CATCHING_CONTESTANT_4A
-	dw EVENT_BUG_CATCHING_CONTESTANT_5A
-	dw EVENT_BUG_CATCHING_CONTESTANT_6A
-	dw EVENT_BUG_CATCHING_CONTESTANT_7A
-	dw EVENT_BUG_CATCHING_CONTESTANT_8A
-	dw EVENT_BUG_CATCHING_CONTESTANT_9A
-	dw EVENT_BUG_CATCHING_CONTESTANT_10A
-; 13a12
+INCLUDE "data/bug_contest_flags.asm"
 
 ContestDropOffMons: ; 13a12
 	ld hl, PartyMon1HP
@@ -101,7 +90,7 @@ ContestDropOffMons: ; 13a12
 	ld a, [hl]
 	ld [wBugContestSecondPartySpecies], a
 ; ... and replacing it with the terminator byte
-	ld [hl], $ff
+	ld [hl], -1
 	xor a
 	ld [ScriptVar], a
 	ret
@@ -118,7 +107,7 @@ ContestReturnMons: ; 13a31
 	ld a, [wBugContestSecondPartySpecies]
 	ld [hl], a
 ; Restore the party count, which must be recomputed.
-	ld b, $1
+	ld b, 1
 .loop
 	ld a, [hli]
 	cp -1
diff --git a/engine/events/bug_contest/judging.asm b/engine/events/bug_contest/judging.asm
index 901ae88fa..1db8cd6c6 100755
--- a/engine/events/bug_contest/judging.asm
+++ b/engine/events/bug_contest/judging.asm
@@ -77,9 +77,8 @@ BugContest_ThirdPlaceScoreText: ; 0x1372b
 ; 0x13730
 
 LoadContestantName: ; 13730
-
-; If a = 0, get your name.
-	dec a
+; If a = 1, get your name.
+	dec a ; BUG_CONTEST_PLAYER
 	jr z, .player
 ; Find the pointer for the trainer class of the Bug Catching Contestant whose ID is in a.
 	ld c, a
@@ -141,11 +140,11 @@ INCLUDE "data/bug_contest_winners.asm"
 
 BugContest_GetPlayersResult: ; 13807
 	ld hl, wBugContestThirdPlaceWinnerID
-	ld de, -4
-	ld b, 3
+	ld de, - BUG_CONTESTANT_SIZE
+	ld b, 3 ; 3rd, 2nd, or 1st
 .loop
 	ld a, [hl]
-	cp 1 ; Player
+	cp BUG_CONTEST_PLAYER
 	jr z, .done
 	add hl, de
 	dec b
@@ -159,7 +158,7 @@ BugContest_JudgeContestants: ; 13819
 	call ClearContestResults
 	call ComputeAIContestantScores
 	ld hl, wBugContestTempWinnerID
-	ld a, 1 ; Player
+	ld a, BUG_CONTEST_PLAYER
 	ld [hli], a
 	ld a, [wContestMon]
 	ld [hli], a
@@ -190,11 +189,11 @@ DetermineContestWinners: ; 1383e
 	jr c, .not_first_place
 	ld hl, wBugContestSecondPlaceWinnerID
 	ld de, wBugContestThirdPlaceWinnerID
-	ld bc, 4
+	ld bc, BUG_CONTESTANT_SIZE
 	call CopyBytes
 	ld hl, wBugContestFirstPlaceWinnerID
 	ld de, wBugContestSecondPlaceWinnerID
-	ld bc, 4
+	ld bc, BUG_CONTESTANT_SIZE
 	call CopyBytes
 	ld hl, wBugContestFirstPlaceWinnerID
 	call CopyTempContestant
@@ -208,7 +207,7 @@ DetermineContestWinners: ; 1383e
 	jr c, .not_second_place
 	ld hl, wBugContestSecondPlaceWinnerID
 	ld de, wBugContestThirdPlaceWinnerID
-	ld bc, 4
+	ld bc, BUG_CONTESTANT_SIZE
 	call CopyBytes
 	ld hl, wBugContestSecondPlaceWinnerID
 	call CopyTempContestant
@@ -230,7 +229,7 @@ DetermineContestWinners: ; 1383e
 CopyTempContestant: ; 138a0
 ; Could've just called CopyBytes.
 	ld de, wBugContestTempWinnerID
-rept 3
+rept BUG_CONTESTANT_SIZE +- 1
 	ld a, [de]
 	inc de
 	ld [hli], a
@@ -264,6 +263,7 @@ ComputeAIContestantScores: ; 138b0
 	inc hl
 	inc hl
 .loop2
+	; 0, 1, or 2 for 1st, 2nd, or 3rd
 	call Random
 	and 3
 	cp 3
@@ -278,8 +278,9 @@ ComputeAIContestantScores: ; 138b0
 	ld a, [hli]
 	ld h, [hl]
 	ld l, a
+	; randomly perturb score
 	call Random
-	and 7
+	and %111
 	ld c, a
 	ld b, 0
 	add hl, bc
@@ -294,7 +295,7 @@ ComputeAIContestantScores: ; 138b0
 .done
 	inc e
 	ld a, e
-	cp 10
+	cp NUM_BUG_CONTESTANTS
 	jr nz, .loop
 	ret
 ; 13900
@@ -337,26 +338,26 @@ ContestScore: ; 13900
 	; DVs
 	ld a, [wContestMonDVs + 0]
 	ld b, a
-	and 2
+	and %0010
 	add a
 	add a
 	ld c, a
 
 	swap b
 	ld a, b
-	and 2
+	and %0010
 	add a
 	add c
 	ld d, a
 
 	ld a, [wContestMonDVs + 1]
 	ld b, a
-	and 2
+	and %0010
 	ld c, a
 
 	swap b
 	ld a, b
-	and 2
+	and %0010
 	srl a
 	add c
 	add c
diff --git a/engine/events/fish.asm b/engine/events/fish.asm
index 9d1ea63ae..05bd7f530 100644
--- a/engine/events/fish.asm
+++ b/engine/events/fish.asm
@@ -80,7 +80,7 @@ rept 4
 endr
 
 	ld a, [TimeOfDay]
-	and 3
+	maskbits NUM_DAYTIMES +- 1
 	cp NITE_F
 	jr c, .time_species
 	inc hl
diff --git a/engine/events/magnet_train.asm b/engine/events/magnet_train.asm
index a4b523d1e..fb05ff7f6 100755
--- a/engine/events/magnet_train.asm
+++ b/engine/events/magnet_train.asm
@@ -435,7 +435,7 @@ MagnetTrain_Jumptable_FirstRunThrough: ; 8ceae
 	ld a, [wEnvironment]
 	push af
 	ld a, [TimeOfDay]
-	and $3
+	maskbits NUM_DAYTIMES +- 1
 	ld [TimeOfDayPal], a
 	ld a, $1
 	ld [wEnvironment], a
diff --git a/engine/events/poisonstep_pals.asm b/engine/events/poisonstep_pals.asm
index 10a254ceb..9aad8a9d8 100644
--- a/engine/events/poisonstep_pals.asm
+++ b/engine/events/poisonstep_pals.asm
@@ -10,8 +10,8 @@ LoadPoisonBGPals: ; cbcdd
 	and a
 	jr nz, .cgb
 	ld a, [TimeOfDayPal]
-	and $3
-	cp $3
+	maskbits NUM_DAYTIMES +- 1
+	cp DARKNESS_F
 	ld a, %00000000
 	jr z, .convert_pals
 	ld a, %10101010
diff --git a/engine/events/poke_seer.asm b/engine/events/poke_seer.asm
index d6e335298..4a7b3e081 100644
--- a/engine/events/poke_seer.asm
+++ b/engine/events/poke_seer.asm
@@ -20,7 +20,7 @@ SpecialPokeSeer: ; 4f0bc
 	call PrintSeerText
 	call JoyWaitAorB
 
-	ld b, $6
+	ld b, PARTY_LENGTH
 	farcall SelectMonFromParty
 	jr c, .cancel
 
@@ -163,11 +163,11 @@ GetCaughtLevel: ; 4f18c
 	call ByteFill
 
 	; caught level
-	; Limited to between 1 and 63 for some reason.
+	; Limited to between 1 and 63 since it's a 6-bit quantity.
 	ld a, [wSeerCaughtData]
-	and $3f
+	and CAUGHT_LEVEL_MASK
 	jr z, .unknown
-	cp 1 ; hatched from an egg
+	cp CAUGHT_EGG_LEVEL ; egg marker value
 	jr nz, .print
 	ld a, EGG_LEVEL ; egg hatch level
 
@@ -193,7 +193,7 @@ GetCaughtLevel: ; 4f18c
 
 GetCaughtTime: ; 4f1c5
 	ld a, [wSeerCaughtData]
-	and $c0
+	and CAUGHT_TIME_MASK
 	jr z, .none
 
 	rlca
@@ -233,11 +233,11 @@ UnknownCaughtData: ; 4f1f8
 
 GetCaughtLocation: ; 4f20a
 	ld a, [wSeerCaughtGender]
-	and $7f
+	and CAUGHT_LOCATION_MASK
 	jr z, .Unknown
-	cp $7f
+	cp EVENT_LOCATION
 	jr z, .event
-	cp $7e
+	cp GIFT_LOCATION
 	jr z, .fail
 	ld e, a
 	farcall GetLandmarkName
@@ -440,22 +440,22 @@ GetCaughtGender: ; 4f301
 	add hl, bc
 
 	ld a, [hl]
-	and $7f
+	and CAUGHT_LOCATION_MASK
 	jr z, .genderless
-	cp $7f
+	cp EVENT_LOCATION
 	jr z, .genderless
 
 	ld a, [hl]
-	and $80
+	and CAUGHT_GENDER_MASK
 	jr nz, .male
-	ld c, 1
+	ld c, CAUGHT_BY_GIRL
 	ret
 
 .male
-	ld c, 2
+	ld c, CAUGHT_BY_BOY
 	ret
 
 .genderless
-	ld c, 0
+	ld c, CAUGHT_BY_UNKNOWN
 	ret
 ; 4f31c
diff --git a/engine/intro_menu.asm b/engine/intro_menu.asm
index 8d482f53e..08e004e1b 100755
--- a/engine/intro_menu.asm
+++ b/engine/intro_menu.asm
@@ -1333,7 +1333,7 @@ ResetClock: ; 6392
 Function639b: ; unreferenced
 	; If bit 0 or 1 of [wTitleScreenTimer] is set, we don't need to be here.
 	ld a, [wTitleScreenTimer]
-	and $3
+	and %00000011
 	ret nz
 	ld bc, SpriteAnim10
 	ld hl, SPRITEANIMSTRUCT_FRAME
diff --git a/engine/item_effects.asm b/engine/item_effects.asm
index 7c71cf08a..f5c5e76d1 100644
--- a/engine/item_effects.asm
+++ b/engine/item_effects.asm
@@ -775,7 +775,7 @@ GetPokedexEntryBank:
 	ld a, [EnemyMonSpecies]
 	rlca
 	rlca
-	and 3
+	maskbits NUM_DEX_ENTRY_BANKS +- 1
 	ld hl, .PokedexEntryBanks
 	ld d, 0
 	ld e, a
@@ -786,12 +786,6 @@ GetPokedexEntryBank:
 	ret
 
 .PokedexEntryBanks:
-
-GLOBAL PokedexEntries1
-GLOBAL PokedexEntries2
-GLOBAL PokedexEntries3
-GLOBAL PokedexEntries4
-
 	db BANK(PokedexEntries1)
 	db BANK(PokedexEntries2)
 	db BANK(PokedexEntries3)
diff --git a/engine/landmarks.asm b/engine/landmarks.asm
index 75605bbd9..452bd2e92 100644
--- a/engine/landmarks.asm
+++ b/engine/landmarks.asm
@@ -80,8 +80,8 @@ RegionCheck: ; 0x1caea1
 	jr c, .kanto
 
 .johto
-	ld e, 0
+	ld e, JOHTO_REGION
 	ret
 .kanto
-	ld e, 1
+	ld e, KANTO_REGION
 	ret
diff --git a/engine/map_objects.asm b/engine/map_objects.asm
index 503dac46d..a50650863 100644
--- a/engine/map_objects.asm
+++ b/engine/map_objects.asm
@@ -894,7 +894,7 @@ MapObjectMovementPattern: ; 47dd
 	ld hl, OBJECT_DIRECTION_WALKING
 	add hl, de
 	ld a, [hl]
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	ld d, 1 * 8 + 6
 	cp DOWN
 	jr z, .ok_13
diff --git a/engine/mystery_gift_2.asm b/engine/mystery_gift_2.asm
index 0baaabef3..72767aa17 100755
--- a/engine/mystery_gift_2.asm
+++ b/engine/mystery_gift_2.asm
@@ -29,7 +29,7 @@ PrepMysteryGiftDataToSend: ; 2c642 (b:4642)
 	inc de ; wc80f
 	call CloseSRAM
 	call Random
-	and $1
+	and 1
 	ld [de], a
 	inc de ; wc810
 	call .RandomSample
@@ -59,10 +59,10 @@ PrepMysteryGiftDataToSend: ; 2c642 (b:4642)
 .RandomSample: ; 2c6ac (b:46ac)
 	push de
 	call Random
-	cp $19 ; 10 percent
+	cp 10 percent
 	jr c, .tenpercent
 	call Random
-	and $7
+	and %111
 	ld d, a
 	rl d
 	ld e, $80
@@ -80,10 +80,10 @@ PrepMysteryGiftDataToSend: ; 2c642 (b:4642)
 
 .tenpercent
 	call Random
-	cp $32 ; 20 percent
+	cp 20 percent - 1
 	jr c, .twopercent
 	call Random
-	and $3
+	and %011
 	ld d, a
 	rl d
 	ld e, $80
@@ -102,7 +102,7 @@ PrepMysteryGiftDataToSend: ; 2c642 (b:4642)
 
 .twopercent
 	call Random
-	cp $32 ; 50 ; 20 percent
+	cp 20 percent - 1
 	jr c, .pointfourpercent
 	ld a, b
 	swap a
diff --git a/engine/npc_movement.asm b/engine/npc_movement.asm
index a2508e0f6..dfccc4330 100755
--- a/engine/npc_movement.asm
+++ b/engine/npc_movement.asm
@@ -70,14 +70,14 @@ Function6f07: ; 6f07
 	ld e, [hl]
 	ld hl, OBJECT_PALETTE
 	add hl, bc
-	bit 7, [hl]
+	bit OAM_PRIORITY, [hl]
 	jp nz, Function6fa1
 	ld hl, OBJECT_NEXT_TILE
 	add hl, bc
 	ld a, [hl]
 	ld d, a
 	call GetTileCollision
-	and a ; land
+	and a ; LANDTILE
 	jr z, Function6f3e
 	scf
 	ret
@@ -106,7 +106,7 @@ Function6f3e: ; 6f3e
 	ld hl, OBJECT_DIRECTION_WALKING
 	add hl, bc
 	ld a, [hl]
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	ld e, a
 	ld d, 0
 	ld hl, .data_6f5b
@@ -131,7 +131,7 @@ Function6f5f: ; 6f5f
 	push af
 	ld hl, OBJECT_DIRECTION_WALKING
 	add hl, bc
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	ld e, a
 	ld d, 0
 	ld hl, .data_6f7b
@@ -178,49 +178,49 @@ Function6fa1: ; 6fa1
 	ld hl, OBJECT_DIRECTION_WALKING
 	add hl, bc
 	ld a, [hl]
-	and 3
-	jr z, .asm_6fb2
+	maskbits NUM_DIRECTIONS +- 1
+	jr z, .down
 	dec a
-	jr z, .asm_6fb7
+	jr z, .up
 	dec a
-	jr z, .asm_6fbb
-	jr .asm_6fbf
+	jr z, .left
+	jr .right
 
-.asm_6fb2
+.down
 	inc e
 	push de
 	inc d
-	jr .asm_6fc2
+	jr .continue
 
-.asm_6fb7
+.up
 	push de
 	inc d
-	jr .asm_6fc2
+	jr .continue
 
-.asm_6fbb
+.left
 	push de
 	inc e
-	jr .asm_6fc2
+	jr .continue
 
-.asm_6fbf
+.right
 	inc d
 	push de
 	inc e
 
-.asm_6fc2
+.continue
 	call GetCoordTile
 	call GetTileCollision
 	pop de
-	and a ; land
-	jr nz, .asm_6fd7
+	and a ; LANDTILE
+	jr nz, .not_land
 	call GetCoordTile
 	call GetTileCollision
-	and a ; land
-	jr nz, .asm_6fd7
+	and a ; LANDTILE
+	jr nz, .not_land
 	xor a
 	ret
 
-.asm_6fd7
+.not_land
 	scf
 	ret
 ; 6fd9
diff --git a/engine/npctrade.asm b/engine/npctrade.asm
index 1455dce62..1328efa4c 100755
--- a/engine/npctrade.asm
+++ b/engine/npctrade.asm
@@ -1,11 +1,3 @@
-; Trade dialogs
-	const_def
-	const TRADE_INTRO
-	const TRADE_CANCEL
-	const TRADE_WRONG
-	const TRADE_COMPLETE
-	const TRADE_AFTER
-
 NPCTrade:: ; fcba8
 	ld a, e
 	ld [wJumptableIndex], a
@@ -83,9 +75,9 @@ CheckTradeGender: ; fcc23
 	ld e, TRADE_GENDER
 	call GetTradeAttribute
 	ld a, [hl]
-	and a
+	and a ; TRADE_EITHER_GENDER
 	jr z, .matching
-	cp 1
+	cp TRADE_MALE_ONLY
 	jr z, .check_male
 
 	farcall GetGender
@@ -178,10 +170,10 @@ DoNPCTrade: ; fcc63
 	ld e, TRADE_DIALOG
 	call GetTradeAttribute
 	ld a, [hl]
-	cp 3
-	ld a, 1
+	cp TRADE_DIALOG_GIRL
+	ld a, CAUGHT_BY_GIRL
 	jr c, .okay
-	ld a, 2
+	ld a, CAUGHT_BY_BOY
 .okay
 	ld [wOTTrademonCaughtData], a
 
@@ -400,7 +392,7 @@ GetTradeMonNames: ; fce1b
 	and a
 	ret z
 
-	cp 1
+	cp TRADE_MALE_ONLY
 	ld a, "♂"
 	jr z, .done
 	ld a, "♀"
@@ -433,31 +425,28 @@ PrintTradeText: ; fcf38
 ; fcf53
 
 TradeTexts: ; fcf53
-; intro
+; entries correspond to TRADE_* × TRADE_DIALOG_* constants
+; TRADE_INTRO
 	dw TradeIntroText1
 	dw TradeIntroText2
 	dw TradeIntroText3
 	dw TradeIntroText4
-
-; cancel
+; TRADE_CANCEL
 	dw TradeCancelText1
 	dw TradeCancelText2
 	dw TradeCancelText3
 	dw TradeCancelText4
-
-; wrong mon
+; TRADE_WRONG
 	dw TradeWrongText1
 	dw TradeWrongText2
 	dw TradeWrongText3
 	dw TradeWrongText4
-
-; completed
+; TRADE_COMPLETE
 	dw TradeCompleteText1
 	dw TradeCompleteText2
 	dw TradeCompleteText3
 	dw TradeCompleteText4
-
-; after
+; TRADE_AFTER
 	dw TradeAfterText1
 	dw TradeAfterText2
 	dw TradeAfterText3
diff --git a/engine/pack.asm b/engine/pack.asm
index 047924cb0..ea2a06cb9 100644
--- a/engine/pack.asm
+++ b/engine/pack.asm
@@ -1,3 +1,17 @@
+; Pack.Jumptable and BattlePack.Jumptable indexes
+	const_def
+	const PACKSTATE_INITGFX            ;  0
+	const PACKSTATE_INITITEMSPOCKET    ;  1
+	const PACKSTATE_ITEMSPOCKETMENU    ;  2
+	const PACKSTATE_INITBALLSPOCKET    ;  3
+	const PACKSTATE_BALLSPOCKETMENU    ;  4
+	const PACKSTATE_INITKEYITEMSPOCKET ;  5
+	const PACKSTATE_KEYITEMSPOCKETMENU ;  6
+	const PACKSTATE_INITTMHMPOCKET     ;  7
+	const PACKSTATE_TMHMPOCKETMENU     ;  8
+	const PACKSTATE_QUITNOSCRIPT       ;  9
+	const PACKSTATE_QUITRUNSCRIPT      ; 10
+
 Pack: ; 10000
 	ld hl, Options
 	set NO_TEXT_SCROLL, [hl]
@@ -28,6 +42,7 @@ Pack: ; 10000
 ; 10030
 
 .Jumptable: ; 10030 (4:4030)
+; entries correspond to PACKSTATE_* constants
 	dw .InitGFX            ;  0
 	dw .InitItemsPocket    ;  1
 	dw .ItemsPocketMenu    ;  2
@@ -50,7 +65,7 @@ Pack: ; 10000
 	ret
 
 .InitItemsPocket: ; 10056 (4:4056)
-	xor a
+	xor a ; ITEM_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -70,15 +85,15 @@ Pack: ; 10000
 	ld [wItemsPocketScrollPosition], a
 	ld a, [wMenuCursorY]
 	ld [wItemsPocketCursor], a
-	ld b, $7
-	ld c, $3
+	ld b, PACKSTATE_INITTMHMPOCKET ; left
+	ld c, PACKSTATE_INITBALLSPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	call .ItemBallsKey_LoadSubmenu
 	ret
 
 .InitKeyItemsPocket: ; 10094 (4:4094)
-	ld a, $2
+	ld a, KEY_ITEM_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -98,15 +113,15 @@ Pack: ; 10000
 	ld [wKeyItemsPocketScrollPosition], a
 	ld a, [wMenuCursorY]
 	ld [wKeyItemsPocketCursor], a
-	ld b, $3
-	ld c, $7
+	ld b, PACKSTATE_INITBALLSPOCKET ; left
+	ld c, PACKSTATE_INITTMHMPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	call .ItemBallsKey_LoadSubmenu
 	ret
 
 .InitTMHMPocket: ; 100d3 (4:40d3)
-	ld a, $3
+	ld a, TM_HM_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -118,8 +133,8 @@ Pack: ; 10000
 
 .TMHMPocketMenu: ; 100e8 (4:40e8)
 	farcall TMHMPocket
-	ld b, $5
-	ld c, $1
+	ld b, PACKSTATE_INITKEYITEMSPOCKET ; left
+	ld c, PACKSTATE_INITITEMSPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	farcall _CheckTossableItem
@@ -162,7 +177,6 @@ Pack: ; 10000
 ; 0x10137
 
 .Jumptable1: ; 10137
-
 	dw .UseItem
 	dw QuitItemSubmenu
 
@@ -211,7 +225,7 @@ Pack: ; 10000
 	ret
 
 .InitBallsPocket: ; 10186 (4:4186)
-	ld a, $1
+	ld a, BALL_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -231,8 +245,8 @@ Pack: ; 10000
 	ld [wBallsPocketScrollPosition], a
 	ld a, [wMenuCursorY]
 	ld [wBallsPocketCursor], a
-	ld b, $1
-	ld c, $5
+	ld b, PACKSTATE_INITITEMSPOCKET ; left
+	ld c, PACKSTATE_INITKEYITEMSPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	call .ItemBallsKey_LoadSubmenu
@@ -327,7 +341,6 @@ MenuDataHeader_UsableKeyItem: ; 0x10249
 ; 0x1026a
 
 Jumptable_UseGiveTossRegisterQuit: ; 1026a
-
 	dw UseItem
 	dw GiveItem
 	dw TossMenu
@@ -353,7 +366,6 @@ MenuDataHeader_UsableItem: ; 0x10274
 ; 0x10291
 
 Jumptable_UseGiveTossQuit: ; 10291
-
 	dw UseItem
 	dw GiveItem
 	dw TossMenu
@@ -376,7 +388,6 @@ MenuDataHeader_UnusableItem: ; 0x10299
 ; 0x102ac
 
 Jumptable_UseQuit: ; 102ac
-
 	dw UseItem
 	dw QuitItemSubmenu
 ; 102b0
@@ -398,7 +409,6 @@ MenuDataHeader_UnusableKeyItem: ; 0x102b0
 ; 0x102c7
 
 Jumptable_UseRegisterQuit: ; 102c7
-
 	dw UseItem
 	dw RegisterItem
 	dw QuitItemSubmenu
@@ -422,7 +432,6 @@ MenuDataHeader_HoldableKeyItem: ; 0x102cd
 ; 0x102ea
 
 Jumptable_GiveTossRegisterQuit: ; 102ea
-
 	dw GiveItem
 	dw TossMenu
 	dw RegisterItem
@@ -446,7 +455,6 @@ MenuDataHeader_HoldableItem: ; 0x102f2
 ; 0x1030b
 
 Jumptable_GiveTossQuit: ; 1030b
-
 	dw GiveItem
 	dw TossMenu
 	dw QuitItemSubmenu
@@ -462,14 +470,14 @@ UseItem: ; 10311
 ; 1031f
 
 .dw ; 1031f (4:431f)
-
+; entries correspond to ITEMMENU_* constants
+	dw .Oak     ; ITEMMENU_NOUSE
 	dw .Oak
 	dw .Oak
 	dw .Oak
-	dw .Oak
-	dw .Current
-	dw .Party
-	dw .Field
+	dw .Current ; ITEMMENU_CURRENT
+	dw .Party   ; ITEMMENU_PARTY
+	dw .Field   ; ITEMMENU_CLOSE
 ; 1035c
 
 .Oak: ; 1032d (4:432d)
@@ -503,7 +511,7 @@ UseItem: ; 10311
 	ld a, [wItemEffectSucceeded]
 	and a
 	jr z, .Oak
-	ld a, $a
+	ld a, PACKSTATE_QUITRUNSCRIPT
 	ld [wJumptableIndex], a
 	ret
 ; 10364 (4:4364)
@@ -537,11 +545,11 @@ TossMenu: ; 10364
 ResetPocketCursorPositions: ; 1039d
 ; unreferenced
 	ld a, [wCurrPocket]
-	and a
+	and a ; ITEM_POCKET
 	jr z, .items
-	dec a
+	dec a ; BALL_POCKET
 	jr z, .balls
-	dec a
+	dec a ; KEY_ITEM_POCKET
 	jr z, .key
 	ret
 
@@ -693,6 +701,7 @@ BattlePack: ; 10493
 ; 104c3
 
 .Jumptable: ; 104c3 (4:44c3)
+; entries correspond to PACKSTATE_* constants
 	dw .InitGFX            ;  0
 	dw .InitItemsPocket    ;  1
 	dw .ItemsPocketMenu    ;  2
@@ -715,7 +724,7 @@ BattlePack: ; 10493
 	ret
 
 .InitItemsPocket: ; 104e9 (4:44e9)
-	xor a
+	xor a ; ITEM_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -735,15 +744,15 @@ BattlePack: ; 10493
 	ld [wItemsPocketScrollPosition], a
 	ld a, [wMenuCursorY]
 	ld [wItemsPocketCursor], a
-	ld b, $7
-	ld c, $3
+	ld b, PACKSTATE_INITTMHMPOCKET ; left
+	ld c, PACKSTATE_INITBALLSPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	call ItemSubmenu
 	ret
 
 .InitKeyItemsPocket: ; 10527 (4:4527)
-	ld a, $2
+	ld a, KEY_ITEM_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -763,15 +772,15 @@ BattlePack: ; 10493
 	ld [wKeyItemsPocketScrollPosition], a
 	ld a, [wMenuCursorY]
 	ld [wKeyItemsPocketCursor], a
-	ld b, $3
-	ld c, $7
+	ld b, PACKSTATE_INITBALLSPOCKET ; left
+	ld c, PACKSTATE_INITTMHMPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	call ItemSubmenu
 	ret
 
 .InitTMHMPocket: ; 10566 (4:4566)
-	ld a, $3
+	ld a, TM_HM_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -785,8 +794,8 @@ BattlePack: ; 10493
 
 .TMHMPocketMenu: ; 10581 (4:4581)
 	farcall TMHMPocket
-	ld b, $5
-	ld c, $1
+	ld b, PACKSTATE_INITKEYITEMSPOCKET ; left
+	ld c, PACKSTATE_INITITEMSPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	xor a
@@ -794,7 +803,7 @@ BattlePack: ; 10493
 	ret
 
 .InitBallsPocket: ; 10594 (4:4594)
-	ld a, $1
+	ld a, BALL_POCKET
 	ld [wCurrPocket], a
 	call ClearPocketList
 	call DrawPocketName
@@ -814,8 +823,8 @@ BattlePack: ; 10493
 	ld [wBallsPocketScrollPosition], a
 	ld a, [wMenuCursorY]
 	ld [wBallsPocketCursor], a
-	ld b, $1
-	ld c, $5
+	ld b, PACKSTATE_INITITEMSPOCKET ; left
+	ld c, PACKSTATE_INITKEYITEMSPOCKET ; right
 	call Pack_InterpretJoypad
 	ret c
 	call ItemSubmenu
@@ -893,13 +902,14 @@ TMHMSubmenu: ; 105dc (4:45dc)
 	ret
 
 .ItemFunctionJumptable: ; 10637 (4:4637)
+; entries correspond to ITEMMENU_* constants
+	dw .Oak         ; ITEMMENU_NOUSE
 	dw .Oak
 	dw .Oak
 	dw .Oak
-	dw .Oak
-	dw .Unused
-	dw .BattleField
-	dw .BattleOnly
+	dw .Unused      ; ITEMMENU_CURRENT
+	dw .BattleField ; ITEMMENU_PARTY
+	dw .BattleOnly  ; ITEMMENU_CLOSE
 
 .Oak: ; 10645 (4:4645)
 	ld hl, Text_ThisIsntTheTime
@@ -937,7 +947,7 @@ TMHMSubmenu: ; 105dc (4:45dc)
 	cp $2
 	jr z, .didnt_use_item
 .quit_run_script ; 1067e (4:467e)
-	ld a, 10
+	ld a, PACKSTATE_QUITRUNSCRIPT
 	ld [wJumptableIndex], a
 	ret
 
@@ -954,7 +964,7 @@ InitPackBuffers: ; 1068a
 	xor a
 	ld [wJumptableIndex], a
 	ld a, [wLastPocket]
-	and $3
+	maskbits NUM_POCKETS +- 1
 	ld [wCurrPocket], a
 	inc a
 	add a
@@ -997,13 +1007,14 @@ DepositSellPack: ; 106be
 ; 106d1
 
 .Jumptable: ; 106d1 (4:46d1)
+; entries correspond to *_POCKET constants
 	dw .ItemsPocket
 	dw .BallsPocket
 	dw .KeyItemsPocket
 	dw .TMHMPocket
 
 .ItemsPocket: ; 106d9 (4:46d9)
-	xor a
+	xor a ; ITEM_POCKET
 	call InitPocket
 	ld hl, PC_Mart_ItemsPocketMenuDataHeader
 	call CopyMenuDataHeader
@@ -1019,7 +1030,7 @@ DepositSellPack: ; 106be
 	ret
 
 .KeyItemsPocket: ; 106ff (4:46ff)
-	ld a, 2
+	ld a, KEY_ITEM_POCKET
 	call InitPocket
 	ld hl, PC_Mart_KeyItemsPocketMenuDataHeader
 	call CopyMenuDataHeader
@@ -1035,7 +1046,7 @@ DepositSellPack: ; 106be
 	ret
 
 .TMHMPocket: ; 10726 (4:4726)
-	ld a, 3
+	ld a, TM_HM_POCKET
 	call InitPocket
 	call WaitBGMap_DrawPackGFX
 	farcall TMHMPocket
@@ -1044,7 +1055,7 @@ DepositSellPack: ; 106be
 	ret
 
 .BallsPocket: ; 1073b (4:473b)
-	ld a, 1
+	ld a, BALL_POCKET
 	call InitPocket
 	ld hl, PC_Mart_BallsPocketMenuDataHeader
 	call CopyMenuDataHeader
@@ -1098,7 +1109,7 @@ DepositSellTutorial_InterpretJoypad: ; 1076f
 .d_left
 	ld a, [wJumptableIndex]
 	dec a
-	and $3
+	maskbits NUM_POCKETS +- 1
 	ld [wJumptableIndex], a
 	push de
 	ld de, SFX_SWITCH_POCKETS
@@ -1110,7 +1121,7 @@ DepositSellTutorial_InterpretJoypad: ; 1076f
 .d_right
 	ld a, [wJumptableIndex]
 	inc a
-	and $3
+	maskbits NUM_POCKETS +- 1
 	ld [wJumptableIndex], a
 	push de
 	ld de, SFX_SWITCH_POCKETS
@@ -1144,14 +1155,14 @@ TutorialPack: ; 107bb
 ; 107e1
 
 .dw ; 107e1 (4:47e1)
-
+; entries correspond to *_POCKET constants
 	dw .Items
 	dw .Balls
 	dw .KeyItems
 	dw .TMHM
 
 .Items: ; 107e9 (4:47e9)
-	xor a
+	xor a ; ITEM_POCKET
 	ld hl, .ItemsMenuDataHeader
 	jr .DisplayPocket
 
@@ -1175,7 +1186,7 @@ TutorialPack: ; 107bb
 ; 10807
 
 .KeyItems: ; 10807 (4:4807)
-	ld a, 2
+	ld a, KEY_ITEM_POCKET
 	ld hl, .KeyItemsMenuDataHeader
 	jr .DisplayPocket
 
@@ -1199,7 +1210,7 @@ TutorialPack: ; 107bb
 ; 10826
 
 .TMHM: ; 10826 (4:4826)
-	ld a, 3
+	ld a, TM_HM_POCKET
 	call InitPocket
 	call WaitBGMap_DrawPackGFX
 	farcall TMHMPocket
@@ -1208,7 +1219,7 @@ TutorialPack: ; 107bb
 	ret
 
 .Balls: ; 1083b (4:483b)
-	ld a, 1
+	ld a, BALL_POCKET
 	ld hl, .BallsMenuDataHeader
 	jr .DisplayPocket
 
@@ -1283,7 +1294,7 @@ WaitBGMap_DrawPackGFX: ; 1089a (4:489a)
 	call WaitBGMap
 DrawPackGFX: ; 1089d
 	ld a, [wCurrPocket]
-	and $3
+	maskbits NUM_POCKETS +- 1
 	ld e, a
 	ld d, $0
 	ld a, [BattleType]
@@ -1310,10 +1321,10 @@ DrawPackGFX: ; 1089d
 ; 108cc
 
 PackGFXPointers: ; 108cc
-	dw PackGFX + (15 tiles) * 1
-	dw PackGFX + (15 tiles) * 3
-	dw PackGFX + (15 tiles) * 0
-	dw PackGFX + (15 tiles) * 2
+	dw PackGFX + (15 tiles) * 1 ; ITEM_POCKET
+	dw PackGFX + (15 tiles) * 3 ; BALL_POCKET
+	dw PackGFX + (15 tiles) * 0 ; KEY_ITEM_POCKET
+	dw PackGFX + (15 tiles) * 2 ; TM_HM_POCKET
 ; 108d4
 
 Pack_InterpretJoypad: ; 108d4 (4:48d4)
@@ -1344,7 +1355,7 @@ Pack_InterpretJoypad: ; 108d4 (4:48d4)
 	ret
 
 .b_button
-	ld a, 9
+	ld a, PACKSTATE_QUITNOSCRIPT
 	ld [wJumptableIndex], a
 	scf
 	ret
@@ -1489,15 +1500,19 @@ DrawPocketName: ; 109bb
 ; 109e1
 
 .tilemap ; 109e1
+; ITEM_POCKET
 	db $00, $04, $04, $04, $01 ; top border
 	db $06, $07, $08, $09, $0a ; Items
 	db $02, $05, $05, $05, $03 ; bottom border
+; BALL_POCKET
 	db $00, $04, $04, $04, $01 ; top border
 	db $15, $16, $17, $18, $19 ; Balls
 	db $02, $05, $05, $05, $03 ; bottom border
+; KEY_ITEM_POCKET
 	db $00, $04, $04, $04, $01 ; top border
 	db $0b, $0c, $0d, $0e, $0f ; Key Items
 	db $02, $05, $05, $05, $03 ; bottom border
+; TM_HM_POCKET
 	db $00, $04, $04, $04, $01 ; top border
 	db $10, $11, $12, $13, $14 ; TM/HM
 	db $02, $05, $05, $05, $03 ; bottom border
diff --git a/engine/player_movement.asm b/engine/player_movement.asm
index fa7cc84a5..49fb23f3a 100755
--- a/engine/player_movement.asm
+++ b/engine/player_movement.asm
@@ -140,7 +140,7 @@ DoPlayerMovement:: ; 80000
 
 .water
 	ld a, c
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	ld c, a
 	ld b, 0
 	ld hl, .water_table
@@ -244,7 +244,7 @@ DoPlayerMovement:: ; 80000
 	ld a, [PlayerDirection]
 	rrca
 	rrca
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	cp e
 	jr z, .not_turning
 
@@ -430,7 +430,7 @@ DoPlayerMovement:: ; 80000
 	ld a, [PlayerDirection]
 	rrca
 	rrca
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	cp e
 	jr nz, .not_warp
 	call WarpCheck
@@ -559,7 +559,7 @@ DoPlayerMovement:: ; 80000
 	cp 0
 	ret z
 
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	ld e, a
 	ld d, 0
 	ld hl, .forced_dpad
diff --git a/engine/player_object.asm b/engine/player_object.asm
index 6d5cb7e84..50cabadf6 100755
--- a/engine/player_object.asm
+++ b/engine/player_object.asm
@@ -589,7 +589,7 @@ Special_SurfStartStep: ; 8379
 	ld a, [PlayerDirection]
 	srl a
 	srl a
-	and 3
+	maskbits NUM_DIRECTIONS +- 1
 	ld e, a
 	ld d, 0
 	ld hl, .movement_data
diff --git a/engine/player_step.asm b/engine/player_step.asm
index 996a9b422..fb00a1b81 100755
--- a/engine/player_step.asm
+++ b/engine/player_step.asm
@@ -154,7 +154,7 @@ UpdateOverworldMap: ; d536 (3:5536)
 	jr nc, .not_overflowed
 	ld a, [wBGMapAnchor + 1]
 	inc a
-	and $3
+	and %11
 	or HIGH(vBGMap0)
 	ld [wBGMapAnchor + 1], a
 .not_overflowed
@@ -185,7 +185,7 @@ UpdateOverworldMap: ; d536 (3:5536)
 	jr nc, .not_underflowed
 	ld a, [wBGMapAnchor + 1]
 	dec a
-	and $3
+	and %11
 	or HIGH(vBGMap0)
 	ld [wBGMapAnchor + 1], a
 .not_underflowed
diff --git a/engine/pokedex.asm b/engine/pokedex.asm
index 8f39a742d..7fe3852ed 100644
--- a/engine/pokedex.asm
+++ b/engine/pokedex.asm
@@ -1,3 +1,4 @@
+; Pokedex_RunJumptable.Jumptable indexes
 	const_def
 	const DEXSTATE_MAIN_SCR
 	const DEXSTATE_UPDATE_MAIN_SCR
@@ -185,6 +186,7 @@ Pokedex_RunJumptable: ; 4010b
 	jp hl
 
 .Jumptable: ; 40115 (10:4115)
+; entries correspond to DEXSTATE_* constants
 	dw Pokedex_InitMainScreen
 	dw Pokedex_UpdateMainScreen
 	dw Pokedex_InitDexEntryScreen
@@ -739,7 +741,7 @@ Pokedex_InitSearchResultsScreen: ; 4050a (10:450a)
 	farcall DrawPokedexSearchResultsWindow
 	call Pokedex_PlaceSearchResultsTypeStrings
 	call Pokedex_UpdateSearchResultsCursorOAM
-	ld a, $ff
+	ld a, -1
 	ld [CurPartySpecies], a
 	ld a, SCGB_POKEDEX
 	call Pokedex_GetSGBLayout
@@ -1123,13 +1125,14 @@ Pokedex_DrawMainScreenBG: ; 4074c (10:474c)
 	ret
 
 String_SEEN: ; 407e1
-	db "SEEN", $ff
+	db "SEEN", -1
 String_OWN: ; 407e6
-	db "OWN", $ff
+	db "OWN", -1
 String_SELECT_OPTION: ; 407ea
 	db $3b, $48, $49, $4a, $44, $45, $46, $47 ; SELECT > OPTION
+	; fallthrough
 String_START_SEARCH: ; 407f2
-	db $3c, $3b, $41, $42, $43, $4b, $4c, $4d, $4e, $3c, $ff ; START > SEARCH
+	db $3c, $3b, $41, $42, $43, $4b, $4c, $4d, $4e, $3c, -1 ; START > SEARCH
 
 Pokedex_DrawDexEntryScreenBG: ; 407fd
 	call Pokedex_FillBackgroundColor2
@@ -1164,13 +1167,13 @@ Pokedex_DrawDexEntryScreenBG: ; 407fd
 	ret
 
 .Unused: ; 4084f
-	db $5c, $5d, $ff ; No.
+	db $5c, $5d, -1 ; No.
 .Height: ; 40852
-	db "HT  ?", $5e, "??", $5f, $ff ; HT  ?'??"
+	db "HT  ?", $5e, "??", $5f, -1 ; HT  ?'??"
 .Weight: ; 4085c
-	db "WT   ???lb", $ff ; WT   ???lb
+	db "WT   ???lb", -1 ; WT   ???lb
 .MenuItems: ; 40867
-	db $3b, " PAGE AREA CRY PRNT", $ff
+	db $3b, " PAGE AREA CRY PRNT", -1
 
 Pokedex_DrawOptionScreenBG: ; 4087c (10:487c)
 	call Pokedex_FillBackgroundColor2
@@ -1195,7 +1198,7 @@ Pokedex_DrawOptionScreenBG: ; 4087c (10:487c)
 	ret
 
 .Title: ; 408b2
-	db $3b, " OPTION ", $3c, $ff
+	db $3b, " OPTION ", $3c, -1
 
 .Modes: ; 408bd
 	db   "NEW #DEX MODE"
@@ -1229,10 +1232,10 @@ Pokedex_DrawSearchScreenBG: ; 408f0 (10:48f0)
 	ret
 
 .Title: ; 4092a
-	db $3b, " SEARCH ", $3c, $ff
+	db $3b, " SEARCH ", $3c, -1
 
 .TypeLeftRightArrows: ; 40935
-	db $3d, "        ", $3e, $ff
+	db $3d, "        ", $3e, -1
 
 .Types: ; 40940
 	db   "TYPE1"
diff --git a/engine/pokedex_2.asm b/engine/pokedex_2.asm
index df0771e07..4a5a08803 100644
--- a/engine/pokedex_2.asm
+++ b/engine/pokedex_2.asm
@@ -230,7 +230,7 @@ GetDexEntryPointer: ; 44333
 	push de
 	rlca
 	rlca
-	and $3
+	maskbits NUM_DEX_ENTRY_BANKS +- 1
 	ld hl, .PokedexEntryBanks
 	ld d, 0
 	ld e, a
@@ -241,12 +241,6 @@ GetDexEntryPointer: ; 44333
 	ret
 
 .PokedexEntryBanks: ; 44351
-
-GLOBAL PokedexEntries1
-GLOBAL PokedexEntries2
-GLOBAL PokedexEntries3
-GLOBAL PokedexEntries4
-
 	db BANK(PokedexEntries1)
 	db BANK(PokedexEntries2)
 	db BANK(PokedexEntries3)
diff --git a/engine/pokegear.asm b/engine/pokegear.asm
index 20910c0d5..4141b08fa 100755
--- a/engine/pokegear.asm
+++ b/engine/pokegear.asm
@@ -1,3 +1,27 @@
+; Pokégear cards
+	const_def
+	const POKEGEARCARD_CLOCK ; 0
+	const POKEGEARCARD_MAP   ; 1
+	const POKEGEARCARD_PHONE ; 2
+	const POKEGEARCARD_RADIO ; 3
+NUM_POKEGEAR_CARDS EQU const_value
+
+; PokegearJumptable.Jumptable indexes
+	const_def
+	const POKEGEARSTATE_CLOCKINIT       ; 0
+	const POKEGEARSTATE_CLOCKJOYPAD     ; 1
+	const POKEGEARSTATE_MAPCHECKREGION  ; 2
+	const POKEGEARSTATE_JOHTOMAPINIT    ; 3
+	const POKEGEARSTATE_JOHTOMAPJOYPAD  ; 4
+	const POKEGEARSTATE_KANTOMAPINIT    ; 5
+	const POKEGEARSTATE_KANTOMAPJOYPAD  ; 6
+	const POKEGEARSTATE_PHONEINIT       ; 7
+	const POKEGEARSTATE_PHONEJOYPAD     ; 8
+	const POKEGEARSTATE_MAKEPHONECALL   ; 9
+	const POKEGEARSTATE_FINISHPHONECALL ; a
+	const POKEGEARSTATE_RADIOINIT       ; b
+	const POKEGEARSTATE_RADIOJOYPAD     ; c
+
 PokeGear: ; 90b8d (24:4b8d)
 	ld hl, Options
 	ld a, [hl]
@@ -163,7 +187,10 @@ AnimatePokegearModeIndicatorArrow: ; 90d41 (24:4d41)
 ; 90d52 (24:4d52)
 
 .XCoords: ; 90d52
-	db $00, $10, $20, $30
+	db $00 ; POKEGEARCARD_CLOCK
+	db $10 ; POKEGEARCARD_MAP
+	db $20 ; POKEGEARCARD_PHONE
+	db $30 ; POKEGEARCARD_RADIO
 ; 90d56
 
 TownMap_GetCurrentLandmark: ; 90d56
@@ -210,7 +237,7 @@ TownMap_InitCursorAndPlayerIconPositions: ; 90d70 (24:4d70)
 	ret
 
 Pokegear_InitJumptableIndices: ; 90d9e (24:4d9e)
-	ld a, $0
+	ld a, POKEGEARSTATE_CLOCKINIT
 	ld [wJumptableIndex], a
 	xor a
 	ld [wcf64], a
@@ -224,7 +251,7 @@ InitPokegearTilemap: ; 90da8 (24:4da8)
 	ld a, $4f
 	call ByteFill
 	ld a, [wcf64]
-	and $3
+	maskbits NUM_POKEGEAR_CARDS +- 1
 	add a
 	ld e, a
 	ld d, 0
@@ -260,6 +287,7 @@ InitPokegearTilemap: ; 90da8 (24:4da8)
 	xor a
 .finish
 	ld [hWY], a
+	; swap region maps
 	ld a, [wcf65]
 	and 1
 	xor 1
@@ -281,6 +309,7 @@ InitPokegearTilemap: ; 90da8 (24:4da8)
 ; 90e12 (24:4e12)
 
 .Jumptable: ; 90e12
+; entries correspond to POKEGEARCARD_* constants
 	dw .Clock
 	dw .Map
 	dw .Phone
@@ -319,12 +348,12 @@ InitPokegearTilemap: ; 90da8 (24:4da8)
 	ld e, 1
 .ok
 	farcall PokegearMap
-	ld a, $7
+	ld a, $07
 	ld bc, $12
 	hlcoord 1, 2
 	call ByteFill
 	hlcoord 0, 2
-	ld [hl], $6
+	ld [hl], $06
 	hlcoord 19, 2
 	ld [hl], $17
 	ld a, [wPokegearMapCursorLandmark]
@@ -382,13 +411,13 @@ Pokegear_FinishTilemap: ; 90eb0 (24:4eb0)
 	call ByteFill
 	ld de, wPokegearFlags
 	ld a, [de]
-	bit 0, a
+	bit 0, a ; ENGINE_MAP_CARD
 	call nz, .PlaceMapIcon
 	ld a, [de]
-	bit 2, a
+	bit 2, a ; ENGINE_PHONE_CARD
 	call nz, .PlacePhoneIcon
 	ld a, [de]
-	bit 1, a
+	bit 1, a ; ENGINE_RADIO_CARD
 	call nz, .PlaceRadioIcon
 	hlcoord 0, 0
 	ld a, $46
@@ -433,6 +462,7 @@ PokegearJumptable: ; 90f04 (24:4f04)
 	jp hl
 
 .Jumptable: ; 90f13 (24:4f13)
+; entries correspond to POKEGEARSTATE_* constants
 	dw PokegearClock_Init
 	dw PokegearClock_Joypad
 	dw PokegearMap_CheckRegion
@@ -460,32 +490,32 @@ PokegearClock_Joypad: ; 90f3e (24:4f3e)
 	call .UpdateClock
 	ld hl, hJoyLast
 	ld a, [hl]
-	and A_BUTTON + B_BUTTON + START + SELECT
+	and A_BUTTON | B_BUTTON | START | SELECT
 	jr nz, .quit
 	ld a, [hl]
 	and D_RIGHT
 	ret z
 	ld a, [wPokegearFlags]
-	bit 0, a
+	bit 0, a ; ENGINE_MAP_CARD
 	jr z, .no_map_card
-	ld c, $2
-	ld b, $1
+	ld c, POKEGEARSTATE_MAPCHECKREGION
+	ld b, POKEGEARCARD_MAP
 	jr .done
 
 .no_map_card
 	ld a, [wPokegearFlags]
-	bit 2, a
+	bit 2, a ; ENGINE_PHONE_CARD
 	jr z, .no_phone_card
-	ld c, $7
-	ld b, $2
+	ld c, POKEGEARSTATE_PHONEINIT
+	ld b, POKEGEARCARD_PHONE
 	jr .done
 
 .no_phone_card
 	ld a, [wPokegearFlags]
-	bit 1, a
+	bit 1, a ; ENGINE_RADIO_CARD
 	ret z
-	ld c, $b
-	ld b, $3
+	ld c, POKEGEARSTATE_RADIOINIT
+	ld b, POKEGEARCARD_RADIO
 .done
 	call Pokegear_SwitchPage
 	ret
@@ -535,12 +565,12 @@ PokegearMap_CheckRegion: ; 90fb4 (24:4fb4)
 	cp KANTO_LANDMARK
 	jr nc, .kanto
 .johto
-	ld a, 3
+	ld a, POKEGEARSTATE_JOHTOMAPINIT
 	jr .done
 	ret
 
 .kanto
-	ld a, 5
+	ld a, POKEGEARSTATE_KANTOMAPINIT
 .done
 	ld [wJumptableIndex], a
 	call ExitPokegearRadio_HandleMusic
@@ -583,23 +613,23 @@ PokegearMap_ContinueMap: ; 90ff2 (24:4ff2)
 
 .right
 	ld a, [wPokegearFlags]
-	bit 2, a
+	bit 2, a ; ENGINE_PHONE_CARD
 	jr z, .no_phone
-	ld c, $7
-	ld b, $2
+	ld c, POKEGEARSTATE_PHONEINIT
+	ld b, POKEGEARCARD_PHONE
 	jr .done
 
 .no_phone
 	ld a, [wPokegearFlags]
-	bit 1, a
+	bit 1, a ; ENGINE_RADIO_CARD
 	ret z
-	ld c, $b
-	ld b, $3
+	ld c, POKEGEARSTATE_RADIOINIT
+	ld b, POKEGEARCARD_RADIO
 	jr .done
 
 .left
-	ld c, $0
-	ld b, $0
+	ld c, POKEGEARSTATE_CLOCKINIT
+	ld b, POKEGEARCARD_CLOCK
 .done
 	call Pokegear_SwitchPage
 	ret
@@ -657,7 +687,7 @@ PokegearMap_InitPlayerIcon: ; 9106a
 	depixel 0, 0
 	ld b, SPRITE_ANIM_INDEX_RED_WALK
 	ld a, [wPlayerGender]
-	bit 0, a
+	bit 0, a ; ENGINE_PLAYER_IS_FEMALE
 	jr z, .got_gender
 	ld b, SPRITE_ANIM_INDEX_BLUE_WALK
 .got_gender
@@ -688,7 +718,7 @@ PokegearMap_InitCursor: ; 91098
 	call _InitSpriteAnimStruct
 	ld hl, SPRITEANIMSTRUCT_TILE_ID
 	add hl, bc
-	ld [hl], $4
+	ld [hl], $04
 	ld hl, SPRITEANIMSTRUCT_ANIM_SEQ_ID
 	add hl, bc
 	ld [hl], SPRITE_ANIM_SEQ_NULL
@@ -734,7 +764,7 @@ PokegearMap_UpdateCursorPosition: ; 910d4
 
 TownMap_GetKantoLandmarkLimits: ; 910e8
 	ld a, [wStatusFlags]
-	bit 6, a
+	bit 6, a ; ENGINE_CREDITS_SKIP
 	jr z, .not_hof
 	ld d, ROUTE_28
 	ld e, PALLET_TOWN
@@ -754,7 +784,7 @@ PokegearRadio_Init: ; 910f9 (24:50f9)
 	call _InitSpriteAnimStruct
 	ld hl, SPRITEANIMSTRUCT_TILE_ID
 	add hl, bc
-	ld [hl], $8
+	ld [hl], $08
 	call _UpdateRadioStation
 	ld hl, wJumptableIndex
 	inc [hl]
@@ -780,23 +810,23 @@ PokegearRadio_Joypad: ; 91112 (24:5112)
 
 .left
 	ld a, [wPokegearFlags]
-	bit 2, a
+	bit 2, a ; ENGINE_PHONE_CARD
 	jr z, .no_phone
-	ld c, $7
-	ld b, $2
+	ld c, POKEGEARSTATE_PHONEINIT
+	ld b, POKEGEARCARD_PHONE
 	jr .switch_page
 
 .no_phone
 	ld a, [wPokegearFlags]
-	bit 0, a
+	bit 0, a ; ENGINE_MAP_CARD
 	jr z, .no_map
-	ld c, $2
-	ld b, $1
+	ld c, POKEGEARSTATE_MAPCHECKREGION
+	ld b, POKEGEARCARD_MAP
 	jr .switch_page
 
 .no_map
-	ld c, $0
-	ld b, $0
+	ld c, POKEGEARSTATE_CLOCKINIT
+	ld b, POKEGEARCARD_CLOCK
 .switch_page
 	call Pokegear_SwitchPage
 	ret
@@ -839,23 +869,23 @@ PokegearPhone_Joypad: ; 91171 (24:5171)
 
 .left
 	ld a, [wPokegearFlags]
-	bit 0, a
+	bit 0, a ; ENGINE_MAP_CARD
 	jr z, .no_map
-	ld c, $2
-	ld b, $1
+	ld c, POKEGEARSTATE_MAPCHECKREGION
+	ld b, POKEGEARCARD_MAP
 	jr .switch_page
 
 .no_map
-	ld c, $0
-	ld b, $0
+	ld c, POKEGEARSTATE_CLOCKINIT
+	ld b, POKEGEARCARD_CLOCK
 	jr .switch_page
 
 .right
 	ld a, [wPokegearFlags]
-	bit 1, a
+	bit 1, a ; ENGINE_RADIO_CARD
 	ret z
-	ld c, $b
-	ld b, $3
+	ld c, POKEGEARSTATE_RADIOINIT
+	ld b, POKEGEARCARD_RADIO
 .switch_page
 	call Pokegear_SwitchPage
 	ret
@@ -891,7 +921,7 @@ PokegearPhone_Joypad: ; 91171 (24:5171)
 	ret
 
 .quit_submenu
-	ld a, $8
+	ld a, POKEGEARSTATE_PHONEJOYPAD
 	ld [wJumptableIndex], a
 	ret
 
@@ -931,7 +961,7 @@ PokegearPhone_MakePhoneCall: ; 911eb (24:51eb)
 	farcall Phone_NoSignal
 	ld hl, .OutOfServiceArea
 	call PrintText
-	ld a, $8
+	ld a, POKEGEARSTATE_PHONEJOYPAD
 	ld [wJumptableIndex], a
 	ld hl, PokegearText_WhomToCall
 	call PrintText
@@ -958,7 +988,7 @@ PokegearPhone_FinishPhoneCall: ; 91256 (24:5256)
 	and A_BUTTON | B_BUTTON
 	ret z
 	farcall HangUp
-	ld a, $8
+	ld a, POKEGEARSTATE_PHONEJOYPAD
 	ld [wJumptableIndex], a
 	ld hl, PokegearText_WhomToCall
 	call PrintText
@@ -993,7 +1023,7 @@ PokegearPhone_GetDPad: ; 9126d (24:526d)
 .down
 	ld hl, wPokegearPhoneCursorPosition
 	ld a, [hl]
-	cp $3
+	cp 3
 	jr nc, .scroll_page_down
 	inc [hl]
 	jr .done_joypad_same_page
@@ -1001,7 +1031,7 @@ PokegearPhone_GetDPad: ; 9126d (24:526d)
 .scroll_page_down
 	ld hl, wPokegearPhoneScrollPosition
 	ld a, [hl]
-	cp $6
+	cp 6
 	ret nc
 	inc [hl]
 	jr .done_joypad_update_page
@@ -1075,7 +1105,7 @@ PokegearPhone_UpdateDisplayList: ; 912d8 (24:52d8)
 	ld a, [wPokegearPhoneLoadNameBuffer]
 	inc a
 	ld [wPokegearPhoneLoadNameBuffer], a
-	cp $4
+	cp 4
 	jr c, .loop
 	call PokegearPhone_UpdateCursor
 	ret
@@ -1337,9 +1367,9 @@ Pokegear_SwitchPage: ; 91480 (24:5480)
 
 ExitPokegearRadio_HandleMusic: ; 91492
 	ld a, [wPokegearRadioMusicPlaying]
-	cp $fe
+	cp RESTART_MAP_MUSIC
 	jr z, .restart_map_music
-	cp $ff
+	cp ENTER_MAP_MUSIC
 	call z, EnterMapMusic
 	xor a
 	ld [wPokegearRadioMusicPlaying], a
@@ -1364,11 +1394,11 @@ DeleteSpriteAnimStruct2ToEnd: ; 914ab (24:54ab)
 
 Pokegear_LoadTilemapRLE: ; 914bb (24:54bb)
 	; Format: repeat count, tile ID
-	; Terminated with $FF
+	; Terminated with -1
 	hlcoord 0, 0
 .loop
 	ld a, [de]
-	cp $ff
+	cp -1
 	ret z
 	ld b, a
 	inc de
@@ -1560,7 +1590,7 @@ RadioChannels:
 	call .InJohto
 	jr c, .NoSignal
 	ld a, [wPokegearFlags]
-	bit 3, a
+	bit 3, a ; ENGINE_EXPN_CARD
 	jr z, .NoSignal
 	jp LoadStation_PlacesAndPeople
 
@@ -1568,7 +1598,7 @@ RadioChannels:
 	call .InJohto
 	jr c, .NoSignal
 	ld a, [wPokegearFlags]
-	bit 3, a
+	bit 3, a ; ENGINE_EXPN_CARD
 	jr z, .NoSignal
 	jp LoadStation_LetsAllSing
 
@@ -1576,14 +1606,14 @@ RadioChannels:
 	call .InJohto
 	jr c, .NoSignal
 	ld a, [wPokegearFlags]
-	bit 3, a
+	bit 3, a ; ENGINE_EXPN_CARD
 	jr z, .NoSignal
 	jp LoadStation_PokeFluteRadio
 
 .EvolutionRadio:
 ; This station airs in the Lake of Rage area when Rocket are still in Mahogany.
 	ld a, [wStatusFlags]
-	bit 4, a
+	bit 4, a ; ENGINE_ROCKET_SIGNAL_ON_CH20
 	jr z, .NoSignal
 	ld a, [wPokegearMapPlayerIconLandmark]
 	cp MAHOGANY_TOWN
@@ -1669,7 +1699,7 @@ LoadStation_BuenasPassword: ; 917a5 (24:57a5)
 	call Radio_BackUpFarCallParams
 	ld de, NotBuenasPasswordName
 	ld a, [wStatusFlags2]
-	bit 0, a
+	bit 0, a ; ENGINE_ROCKETS_IN_RADIO_TOWER
 	ret z
 	ld de, BuenasPasswordName
 	ret
@@ -1768,7 +1798,7 @@ RadioMusicRestartDE: ; 91854 (24:5854)
 
 RadioMusicRestartPokemonChannel: ; 91868 (24:5868)
 	push de
-	ld a, $fe
+	ld a, RESTART_MAP_MUSIC
 	ld [wPokegearRadioMusicPlaying], a
 	ld de, MUSIC_NONE
 	call PlayMusic
@@ -1799,7 +1829,7 @@ NoRadioStation: ; 91888 (24:5888)
 NoRadioMusic: ; 9189d (24:589d)
 	ld de, MUSIC_NONE
 	call PlayMusic
-	ld a, $ff
+	ld a, ENTER_MAP_MUSIC
 	ld [wPokegearRadioMusicPlaying], a
 	ret
 
@@ -1810,7 +1840,7 @@ NoRadioName: ; 918a9 (24:58a9)
 	lb bc, 3, 18
 	call ClearBox
 	hlcoord 0, 12
-	ld bc, $412
+	lb bc, 4, 18
 	call TextBox
 	ret
 
@@ -1966,26 +1996,26 @@ _TownMap: ; 9191c
 	ld a, [wTownMapPlayerIconLandmark]
 	cp KANTO_LANDMARK
 	jr nc, .kanto2
-	ld e, $0
+	ld e, JOHTO_REGION
 	jr .okay_tilemap
 
 .kanto2
-	ld e, $1
+	ld e, KANTO_REGION
 .okay_tilemap
 	farcall PokegearMap
-	ld a, $7
+	ld a, $07
 	ld bc, 6
 	hlcoord 1, 0
 	call ByteFill
 	hlcoord 0, 0
-	ld [hl], $6
+	ld [hl], $06
 	hlcoord 7, 0
 	ld [hl], $17
 	hlcoord 7, 1
 	ld [hl], $16
 	hlcoord 7, 2
 	ld [hl], $26
-	ld a, $7
+	ld a, $07
 	ld bc, NAME_LENGTH
 	hlcoord 8, 2
 	call ByteFill
@@ -2001,7 +2031,7 @@ PlayRadio: ; 91a53
 	ld hl, Options
 	ld a, [hl]
 	push af
-	set 4, [hl]
+	set NO_TEXT_SCROLL, [hl]
 	call .PlayStation
 	ld c, 100
 	call DelayFrames
@@ -2031,10 +2061,10 @@ PlayRadio: ; 91a53
 ; 91a87
 
 .PlayStation: ; 91a87
-	ld a, -1
-	ld [EnemyTurnsTaken], a
+	ld a, ENTER_MAP_MUSIC
+	ld [wPokegearRadioMusicPlaying], a
 	ld hl, .StationPointers
-	ld d, $0
+	ld d, 0
 	add hl, de
 	add hl, de
 	ld a, [hli]
@@ -2063,6 +2093,7 @@ PlayRadio: ; 91a53
 ; 91ab9
 
 .StationPointers: ; 91ab9
+; entries correspond to radio station constants
 	dw .OakOrPnP
 	dw LoadStation_OaksPokemonTalk
 	dw LoadStation_PokedexShow
@@ -2286,7 +2317,7 @@ TownMapBubble: ; 91bb5
 GetMapCursorCoordinates: ; 91c17
 	ld a, [wTownMapPlayerIconLandmark]
 	ld l, a
-	ld h, $0
+	ld h, 0
 	add hl, hl
 	ld de, Flypoints
 	add hl, de
@@ -2296,10 +2327,10 @@ GetMapCursorCoordinates: ; 91c17
 	ld c, a
 	ld a, [wTownMapCursorCoordinates + 1]
 	ld b, a
-	ld hl, $4
+	ld hl, 4
 	add hl, bc
 	ld [hl], e
-	ld hl, $5
+	ld hl, 5
 	add hl, bc
 	ld [hl], d
 	ret
@@ -2477,7 +2508,7 @@ _Area: ; 91d11
 	call SetPalettes
 	xor a
 	ld [hBGMapMode], a
-	xor a ; Johto
+	xor a ; JOHTO_REGION
 	call .GetAndPlaceNest
 .loop
 	call JoyTextDelay
@@ -2524,13 +2555,13 @@ _Area: ; 91d11
 	call ClearSprites
 	ld a, $90
 	ld [hWY], a
-	xor a ; Johto
+	xor a ; JOHTO_REGION
 	call .GetAndPlaceNest
 	ret
 
 .right
 	ld a, [wStatusFlags]
-	bit 6, a ; hall of fame
+	bit 6, a ; ENGINE_CREDITS_SKIP
 	ret z
 	ld a, [hWY]
 	and a
@@ -2538,7 +2569,7 @@ _Area: ; 91d11
 	call ClearSprites
 	xor a
 	ld [hWY], a
-	ld a, 1 ; Kanto
+	ld a, KANTO_REGION
 	call .GetAndPlaceNest
 	ret
 
@@ -2791,12 +2822,11 @@ TownMapPals: ; 91f13
 ; Current tile
 	ld a, [hli]
 	push hl
-; HP/borders use palette 0
+; The palette map covers tiles $00 to $5f; $60 and above use palette 0
 	cp $60
 	jr nc, .pal0
-; The palette data is condensed to nybbles,
 
-; least-significant first.
+; The palette data is condensed to nybbles, least-significant first.
 	ld hl, .PalMap
 	srl a
 	jr c, .odd
@@ -2807,7 +2837,7 @@ TownMapPals: ; 91f13
 	adc 0
 	ld h, a
 	ld a, [hl]
-	and %111
+	and PALETTE_MASK
 	jr .update
 
 .odd
@@ -2819,7 +2849,7 @@ TownMapPals: ; 91f13
 	ld h, a
 	ld a, [hl]
 	swap a
-	and %111
+	and PALETTE_MASK
 	jr .update
 
 .pal0
@@ -2839,7 +2869,7 @@ INCLUDE "gfx/pokegear/town_map_palette_map.asm"
 ; 91f7b
 
 TownMapMon: ; 91f7b
-; Draw the FlyMon icon at town map location in
+; Draw the FlyMon icon at town map location
 
 ; Get FlyMon species
 	ld a, [CurPartyMon]
@@ -2850,7 +2880,7 @@ TownMapMon: ; 91f7b
 	ld a, [hl]
 	ld [wd265], a
 ; Get FlyMon icon
-	ld e, 8 ; starting tile in VRAM
+	ld e, $08 ; starting tile in VRAM
 	farcall GetSpeciesIcon
 ; Animation/palette
 	depixel 0, 0
@@ -2858,7 +2888,7 @@ TownMapMon: ; 91f7b
 	call _InitSpriteAnimStruct
 	ld hl, SPRITEANIMSTRUCT_TILE_ID
 	add hl, bc
-	ld [hl], $8
+	ld [hl], $08
 	ld hl, SPRITEANIMSTRUCT_ANIM_SEQ_ID
 	add hl, bc
 	ld [hl], SPRITE_ANIM_SEQ_NULL
diff --git a/engine/radio.asm b/engine/radio.asm
index 06cc3a59a..de19a289c 100644
--- a/engine/radio.asm
+++ b/engine/radio.asm
@@ -247,7 +247,7 @@ endr
 	; Generate a number, either 0, 1, or 2, to choose a time of day.
 .loop2
 	call Random
-	and $3
+	maskbits NUM_DAYTIMES +- 1
 	cp DARKNESS_F
 	jr z, .loop2
 
@@ -692,8 +692,8 @@ PokedexShow_GetDexEntryBank:
 	dec a
 	rlca
 	rlca
-	and 3
-	ld hl, .pokedexbanks
+	maskbits NUM_DEX_ENTRY_BANKS +- 1
+	ld hl, .PokedexEntryBanks
 	ld d, 0
 	ld e, a
 	add hl, de
@@ -702,7 +702,7 @@ PokedexShow_GetDexEntryBank:
 	pop hl
 	ret
 
-.pokedexbanks
+.PokedexEntryBanks
 	db BANK(PokedexEntries1)
 	db BANK(PokedexEntries2)
 	db BANK(PokedexEntries3)
diff --git a/engine/routines/drawkrispackgfx.asm b/engine/routines/drawkrispackgfx.asm
index 457dd7110..54a21e447 100644
--- a/engine/routines/drawkrispackgfx.asm
+++ b/engine/routines/drawkrispackgfx.asm
@@ -11,10 +11,10 @@ DrawKrisPackGFX: ; 48e81
 	ret
 
 PackFGFXPointers: ; 48e93
-	dw PackFGFX + (15 tiles) * 1
-	dw PackFGFX + (15 tiles) * 3
-	dw PackFGFX + (15 tiles) * 0
-	dw PackFGFX + (15 tiles) * 2
+	dw PackFGFX + (15 tiles) * 1 ; ITEM_POCKET
+	dw PackFGFX + (15 tiles) * 3 ; BALL_POCKET
+	dw PackFGFX + (15 tiles) * 0 ; KEY_ITEM_POCKET
+	dw PackFGFX + (15 tiles) * 2 ; TM_HM_POCKET
 
 PackFGFX: ; 48e9b
 INCBIN "gfx/pack/pack_f.2bpp"
diff --git a/engine/scripting.asm b/engine/scripting.asm
index b5489917b..a7650351a 100644
--- a/engine/scripting.asm
+++ b/engine/scripting.asm
@@ -614,7 +614,7 @@ GetPocketName:
 	ld a, [wItemAttributeParamBuffer]
 	dec a
 	ld hl, .Pockets
-	and 3
+	maskbits NUM_POCKETS +- 1
 	add a
 	ld e, a
 	ld d, 0
@@ -2474,7 +2474,7 @@ Script_warpfacing:
 ; parameters: facing, map_group, map_id, x, y
 
 	call GetScriptByte
-	and $3
+	maskbits NUM_DIRECTIONS +- 1
 	ld c, a
 	ld a, [wPlayerSpriteSetupFlags]
 	set 5, a
diff --git a/engine/stats_screen.asm b/engine/stats_screen.asm
index 23d1d2d62..8f16c5d71 100755
--- a/engine/stats_screen.asm
+++ b/engine/stats_screen.asm
@@ -1,3 +1,9 @@
+const_value set 1
+	const PINK_PAGE  ; 1
+	const GREEN_PAGE ; 2
+	const BLUE_PAGE  ; 3
+NUM_STAT_PAGES EQU const_value +- 1
+
 BattleStatsScreenInit: ; 4dc7b (13:5c7b)
 	ld a, [wLinkMode]
 	cp LINK_MOBILE
@@ -58,12 +64,12 @@ StatsScreenMain: ; 0x4dcd2
 	; stupid interns
 	ld [wcf64], a
 	ld a, [wcf64]
-	and $fc
-	or $1
+	and %11111100
+	or 1
 	ld [wcf64], a
 .loop ; 4dce3
 	ld a, [wJumptableIndex]
-	and $7f
+	and $ff ^ (1 << 7)
 	ld hl, StatsScreenPointerTable
 	rst JumpTable
 	call StatsScreen_WaitAnim ; check for keys?
@@ -79,13 +85,13 @@ StatsScreenMobile: ; 4dcf7
 	; stupid interns
 	ld [wcf64], a
 	ld a, [wcf64]
-	and $fc
-	or $1
+	and %11111100
+	or 1
 	ld [wcf64], a
 .loop
 	farcall Mobile_SetOverworldDelay
 	ld a, [wJumptableIndex]
-	and $7f
+	and $ff ^ (1 << 7)
 	ld hl, StatsScreenPointerTable
 	rst JumpTable
 	call StatsScreen_WaitAnim
@@ -277,7 +283,7 @@ StatsScreen_GetJoypad: ; 4de2c (13:5e2c)
 StatsScreen_JoypadAction: ; 4de54 (13:5e54)
 	push af
 	ld a, [wcf64]
-	and $3
+	maskbits NUM_STAT_PAGES +- 1
 	ld c, a
 	pop af
 	bit B_BUTTON_F, a
@@ -335,20 +341,20 @@ StatsScreen_JoypadAction: ; 4de54 (13:5e54)
 
 .a_button
 	ld a, c
-	cp $3
+	cp BLUE_PAGE ; last page
 	jr z, .b_button
 .d_right
 	inc c
-	ld a, $3
+	ld a, BLUE_PAGE ; last page
 	cp c
 	jr nc, .set_page
-	ld c, $1
+	ld c, PINK_PAGE ; first page
 	jr .set_page
 
 .d_left
 	dec c
 	jr nz, .set_page
-	ld c, $3
+	ld c, BLUE_PAGE ; last page
 	jr .set_page
 
 .done
@@ -507,7 +513,7 @@ StatsScreen_LoadGFX: ; 4dfb6 (13:5fb6)
 
 .ClearBox: ; 4dfda (13:5fda)
 	ld a, [wcf64]
-	and $3
+	maskbits NUM_STAT_PAGES +- 1
 	ld c, a
 	call StatsScreen_LoadPageIndicators
 	hlcoord 0, 8
@@ -517,7 +523,7 @@ StatsScreen_LoadGFX: ; 4dfb6 (13:5fb6)
 
 .LoadPals: ; 4dfed (13:5fed)
 	ld a, [wcf64]
-	and $3
+	maskbits NUM_STAT_PAGES +- 1
 	ld c, a
 	farcall LoadStatsScreenPals
 	call DelayFrame
@@ -527,13 +533,14 @@ StatsScreen_LoadGFX: ; 4dfb6 (13:5fb6)
 
 .PageTilemap: ; 4e002 (13:6002)
 	ld a, [wcf64]
-	and $3
+	maskbits NUM_STAT_PAGES +- 1
 	dec a
 	ld hl, .Jumptable
 	rst JumpTable
 	ret
 
 .Jumptable: ; 4e00d (13:600d)
+; entries correspond to *_PAGE constants
 	dw .PinkPage
 	dw .GreenPage
 	dw .BluePage
@@ -1089,13 +1096,13 @@ StatsScreen_LoadPageIndicators: ; 4e4cd (13:64cd)
 	ld a, $36
 	call .load_square
 	ld a, c
-	cp $2
+	cp GREEN_PAGE
 	ld a, $3a
-	hlcoord 13, 5
+	hlcoord 13, 5 ; PINK_PAGE (< GREEN_PAGE)
 	jr c, .load_square
-	hlcoord 15, 5
+	hlcoord 15, 5 ; GREEN_PAGE (= GREEN_PAGE)
 	jr z, .load_square
-	hlcoord 17, 5
+	hlcoord 17, 5 ; BLUE_PAGE (> GREEN_PAGE)
 .load_square ; 4e4f7 (13:64f7)
 	push bc
 	ld [hli], a
diff --git a/engine/time.asm b/engine/time.asm
index 799a24f49..03687eee9 100755
--- a/engine/time.asm
+++ b/engine/time.asm
@@ -133,16 +133,16 @@ endr
 Special_SampleKenjiBreakCountdown: ; 11485
 ; Generate a random number between 3 and 6
 	call Random
-	and 3
+	and %11
 	add 3
 	ld [wKenjiBreakTimer], a
 	ret
 ; 11490
 
 StartBugContestTimer: ; 11490
-	ld a, 20
+	ld a, BUG_CONTEST_MINUTES
 	ld [wBugContestMinsRemaining], a
-	ld a, 0
+	ld a, BUG_CONTEST_SECONDS
 	ld [wBugContestSecsRemaining], a
 	call UpdateTime
 	ld hl, wBugContestStartTime
@@ -252,7 +252,7 @@ RestartLuckyNumberCountdown: ; 1152b
 	ld a, FRIDAY
 	sub c
 	jr z, .friday_saturday
-	jr nc, .earlier ; should've done "ret nc"
+	jr nc, .earlier ; could have done "ret nc"
 
 .friday_saturday
 	add 7
diff --git a/engine/trade_animation.asm b/engine/trade_animation.asm
index d5b97d563..f5bd375d1 100755
--- a/engine/trade_animation.asm
+++ b/engine/trade_animation.asm
@@ -1,3 +1,14 @@
+TRADEANIM_RIGHT_ARROW EQU $ed
+TRADEANIM_LEFT_ARROW  EQU $ee
+
+; TradeAnim_TubeAnimJumptable.Jumptable indexes
+	const_def
+	const TRADEANIMSTATE_0 ; 0
+	const TRADEANIMSTATE_1 ; 1
+	const TRADEANIMSTATE_2 ; 2
+	const TRADEANIMSTATE_3 ; 3
+TRADEANIMJUMPTABLE_LENGTH EQU const_value
+
 TradeAnimation: ; 28f24
 	xor a
 	ld [wcf66], a
@@ -165,13 +176,13 @@ RunTradeAnimScript: ; 28fa1
 	ld de, vTiles2 tile $31
 	call Decompress
 	ld hl, TradeArrowGFX
-	ld de, vTiles1 tile $6d
-	ld bc, $10
+	ld de, vTiles0 tile TRADEANIM_RIGHT_ARROW
+	ld bc, 1 tiles
 	ld a, BANK(TradeArrowGFX)
 	call FarCopyBytes
-	ld hl, TradeArrowGFX + $10
-	ld de, vTiles1 tile $6e
-	ld bc, $10
+	ld hl, TradeArrowGFX + 1 tiles
+	ld de, vTiles0 tile TRADEANIM_LEFT_ARROW
+	ld bc, 1 tiles
 	ld a, BANK(TradeArrowGFX)
 	call FarCopyBytes
 	xor a
@@ -317,7 +328,7 @@ TradeAnim_End: ; 29123
 ; 29129
 
 TradeAnim_TubeToOT1: ; 29129
-	ld a, $ed ; >>>>>>>>
+	ld a, TRADEANIM_RIGHT_ARROW
 	call TradeAnim_PlaceTrademonStatsOnTubeAnim
 	ld a, [wLinkTradeSendmonSpecies]
 	ld [wd265], a
@@ -327,11 +338,11 @@ TradeAnim_TubeToOT1: ; 29129
 	jr TradeAnim_InitTubeAnim
 
 TradeAnim_TubeToPlayer1: ; 2913c
-	ld a, $ee ; <<<<<<<<
+	ld a, TRADEANIM_LEFT_ARROW
 	call TradeAnim_PlaceTrademonStatsOnTubeAnim
 	ld a, [wLinkTradeGetmonSpecies]
 	ld [wd265], a
-	ld a, $2
+	ld a, TRADEANIMSTATE_2
 	depixel 9, 18, 4, 4
 	ld b, $4
 TradeAnim_InitTubeAnim: ; 2914e
@@ -400,7 +411,7 @@ TradeAnim_TubeToOT2: ; 291af
 	ld [hSCX], a
 	cp $50
 	ret nz
-	ld a, $1
+	ld a, TRADEANIMSTATE_1
 	call TradeAnim_TubeAnimJumptable
 	call TradeAnim_IncrementJumptableIndex
 	ret
@@ -414,7 +425,7 @@ TradeAnim_TubeToOT3: ; 291c4
 	ld [hSCX], a
 	cp $a0
 	ret nz
-	ld a, $2
+	ld a, TRADEANIMSTATE_2
 	call TradeAnim_TubeAnimJumptable
 	call TradeAnim_IncrementJumptableIndex
 	ret
@@ -440,7 +451,7 @@ TradeAnim_TubeToPlayer3: ; 291e8
 	ld [hSCX], a
 	cp $b0
 	ret nz
-	ld a, $1
+	ld a, TRADEANIMSTATE_1
 	call TradeAnim_TubeAnimJumptable
 	call TradeAnim_IncrementJumptableIndex
 	ret
@@ -454,7 +465,7 @@ TradeAnim_TubeToPlayer4: ; 291fd
 	ld [hSCX], a
 	cp $60
 	ret nz
-	xor a
+	xor a ; TRADEANIMSTATE_0
 	call TradeAnim_TubeAnimJumptable
 	call TradeAnim_IncrementJumptableIndex
 	ret
@@ -541,7 +552,7 @@ TradeAnim_GetTrademonSFX: ; 29277
 ; 29281
 
 TradeAnim_TubeAnimJumptable: ; 29281
-	and 3
+	maskbits TRADEANIMJUMPTABLE_LENGTH +- 1
 	ld e, a
 	ld d, 0
 	ld hl, .Jumptable
@@ -554,6 +565,7 @@ TradeAnim_TubeAnimJumptable: ; 29281
 ; 2928f
 
 .Jumptable: ; 2928f
+; entries correspond to TRADEANIMSTATE_* constants
 	dw .Zero
 	dw .One
 	dw .Two
diff --git a/engine/wildmons.asm b/engine/wildmons.asm
index dc62093b8..33e66ce07 100755
--- a/engine/wildmons.asm
+++ b/engine/wildmons.asm
@@ -678,9 +678,9 @@ UpdateRoamMons: ; 2a30d
 	ld l, e
 ; Choose which map to warp to.
 	call Random
-	and $1f ; 1/8n chance it moves to a completely random map, where n is the number of roaming connections from the current map.
+	and %00011111 ; 1/8n chance it moves to a completely random map, where n is the number of roaming connections from the current map.
 	jr z, JumpRoamMon
-	and 3
+	and %11
 	cp [hl]
 	jr nc, .update_loop ; invalid index, try again
 	inc hl
@@ -739,10 +739,10 @@ JumpRoamMons: ; 2a394
 JumpRoamMon: ; 2a3cd
 .loop
 	ld hl, RoamMaps
-.innerloop1 ; This loop is completely unnecessary.
-	call Random ; Choose a random number
-	and $f ; Take the lower nybble only.  This gives a number between 0 and 15.
-	cp $10 ; If the number is greater than or equal to 16, loop back and try again.
+.innerloop1            ; This loop is completely unnecessary.
+	call Random        ; Choose a random number.
+	maskbits $10 - 1   ; Mask the number to limit it between 0 and 15.
+	cp $10             ; If the number is not less than 16, try again.
 	jr nc, .innerloop1 ; I'm sure you can guess why this check is bogus.
 	inc a
 	ld b, a
@@ -825,7 +825,7 @@ RandomUnseenWildMon: ; 2a4ab
 	call AddNTimes
 .randloop1
 	call Random
-	and $3
+	and %11
 	jr z, .randloop1
 	dec a
 	ld c, a
@@ -902,7 +902,7 @@ RandomPhoneWildMon: ; 2a51f
 
 .done
 	call Random
-	and $3
+	and %11
 	ld c, a
 	ld b, $0
 	add hl, bc
diff --git a/home/map.asm b/home/map.asm
index 287bfcf49..eb061e713 100644
--- a/home/map.asm
+++ b/home/map.asm
@@ -1371,7 +1371,7 @@ UpdateBGMapColumn:: ; 27f8
 	inc d
 ; cap d at HIGH(vBGMap0)
 	ld a, d
-	and $3
+	and %11
 	or HIGH(vBGMap0)
 	ld d, a