Cut release 0.12.0

## Summary

* **What is the goal of this PR?** (e.g., Fixes a bug in the user
authentication module, Implements the new feature for
  file uploading.)
* **What changes are included?**

## Additional Context

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks, specific areas to
focus on).

---------

Co-authored-by: ratedcounsel <hello@ratedcounsel.com>
Co-authored-by: Dave Allie <dave@daveallie.com>

.github/workflows/ci.yml

@@ -12,12 +12,6 @@ jobs:
       - uses: actions/checkout@v6
         with:
           submodules: recursive
-      - uses: actions/cache@v5
-        with:
-          path: |
-            ~/.cache/pip
-            ~/.platformio/.cache
-          key: ${{ runner.os }}-pio
       - uses: actions/setup-python@v6
         with:
           python-version: '3.14'
@@ -34,7 +28,7 @@ jobs:
           sudo apt-get install -y clang-format-21
 
       - name: Run cppcheck
-        run: pio check --fail-on-defect medium --fail-on-defect high
+        run: pio check --fail-on-defect low --fail-on-defect medium --fail-on-defect high
 
       - name: Run clang-format
         run: PATH="/usr/lib/llvm-21/bin:$PATH" ./bin/clang-format-fix && git diff --exit-code || (echo "Please run 'bin/clang-format-fix' to fix formatting issues" && exit 1)

.gitignore

@@ -3,3 +3,4 @@
 .DS_Store
 .vscode
 lib/EpdFont/fontsrc
+*.generated.h

README.md

@@ -23,18 +23,25 @@ CrossPoint Reader aims to:
 
 This project is **not affiliated with Xteink**; it's built as a community project.
 
-## Features
+## Features & Usage
 
-- [x] EPUB parsing and rendering
+- [x] EPUB parsing and rendering (EPUB 2 and EPUB 3)
+- [ ] Image support within EPUB
 - [x] Saved reading position
-- [ ] File explorer with file picker
+- [x] File explorer with file picker
   - [x] Basic EPUB picker from root directory
   - [x] Support nested folders
   - [ ] EPUB picker with cover art
-- [ ] Image support within EPUB
-- [ ] Configurable font, layout, and display options
-- [ ] WiFi connectivity
-- [ ] BLE connectivity
+- [x] Custom sleep screen
+  - [x] Cover sleep screen
+- [x] Wifi book upload
+- [x] Wifi OTA updates
+- [x] Configurable font, layout, and display options
+  - [ ] User provided fonts
+  - [ ] Full UTF support
+- [x] Screen rotation
+
+See [the user guide](./USER_GUIDE.md) for instructions on operating CrossPoint.
 
 ## Installing
 
@@ -59,10 +66,6 @@ back to the other partition using the "Swap boot partition" button here https://
 
 See [Development](#development) below.
 
-## Usage
-
-See [the user guide](./USER_GUIDE.md) for instructions on operating CrossPoint.
-
 ## Development
 
 ### Prerequisites
@@ -97,9 +100,9 @@ CrossPoint Reader is pretty aggressive about caching data down to the SD card to
 has ~380KB of usable RAM, so we have to be careful. A lot of the decisions made in the design of the firmware were based
 on this constraint.
 
-### EPUB caching
+### Data caching
 
-The first time chapters of an EPUB are loaded, they are cached to the SD card. Subsequent loads are served from the 
+The first time chapters of a book are loaded, they are cached to the SD card. Subsequent loads are served from the 
 cache. This cache directory exists at `.crosspoint` on the SD card. The structure is as follows:
 
 
@@ -107,25 +110,22 @@ cache. This cache directory exists at `.crosspoint` on the SD card. The structur
 .crosspoint/
 ├── epub_12471232/       # Each EPUB is cached to a subdirectory named `epub_<hash>`
 │   ├── progress.bin     # Stores reading progress (chapter, page, etc.)
-│   ├── 0/               # Each chapter is stored in a subdirectory named by its index (based on the spine order)
-│   │   ├── section.bin  # Section metadata (page count)
-│   │   ├── page_0.bin   # Each page is stored in a separate file, it
-│   │   ├── page_1.bin   #   contains the position (x, y) and text for each word
-│   │   └── ...
-│   ├── 1/
-│   │   ├── section.bin
-│   │   ├── page_0.bin
-│   │   ├── page_1.bin
-│   │   └── ...
-│   └── ...
+│   ├── cover.bmp        # Book cover image (once generated)
+│   ├── book.bin         # Book metadata (title, author, spine, table of contents, etc.)
+│   └── sections/        # All chapter data is stored in the sections subdirectory
+│       ├── 0.bin        # Chapter data (screen count, all text layout info, etc.)
+│       ├── 1.bin        #     files are named by their index in the spine
+│       └── ...
 │
 └── epub_189013891/
 ```
 
-Deleting the `.crosspoint` directory will clear the cache. 
+Deleting the `.crosspoint` directory will clear the entire cache. 
 
-Due the way it's currently implemented, the cache is not automatically cleared when the EPUB is deleted and moving an 
-EPUB file will reset the reading progress.
+Due the way it's currently implemented, the cache is not automatically cleared when a book is deleted and moving a book
+file will use a new cache directory, resetting the reading progress.
+
+For more details on the internal file structures, see the [file formats document](./docs/file-formats.md).
 
 ## Contributing
 

USER_GUIDE.md

@@ -5,7 +5,7 @@ the device.
 
 ## 1. Hardware Overview
 
-The device utilises the standard buttons on the Xtink X4 in the same layout:
+The device utilises the standard buttons on the Xtink X4 (in the same layout as the manufacturer firmware, by default):
 
 ### Button Layout
 | Location        | Buttons                                    |
@@ -13,30 +13,102 @@ The device utilises the standard buttons on the Xtink X4 in the same layout:
 | **Bottom Edge** | **Back**, **Confirm**, **Left**, **Right** |
 | **Right Side**  | **Power**, **Volume Up**, **Volume Down**  |
 
+Button layout can be customized in **[Settings](#35-settings)**.
+
 ---
 
 ## 2. Power & Startup
 
 ### Power On / Off
 
-To turn the device on or off, **press and hold the Power button for 1 full second**.
+To turn the device on or off, **press and hold the Power button for half a second**. In **[Settings](#35-settings)** you can configure
+the power button to trigger on a short press instead of a long one.
 
 ### First Launch
 
-Upon turning the device on for the first time, you will be placed on the **Book Selection Screen** (File Browser).
+Upon turning the device on for the first time, you will be placed on the **[Home](#31-home-screen)** screen.
 
-> **Note:** On subsequent restarts, the firmware will automatically reopen the last book you were reading.
+> [!NOTE]
+> On subsequent restarts, the firmware will automatically reopen the last book you were reading.
 
 ---
 
-## 3. Book Selection
+## 3. Screens
 
-The Home Screen acts as a folder and file browser.
+### 3.1 Home Screen
+
+The Home Screen is the main entry point to the firmware. From here you can navigate to **[Reading Mode](#4-reading-mode)** with the most recently read book, **[Book Selection](#32-book-selection)**,
+**[Settings](#35-settings)**, or the **[File Upload](#34-file-upload-screen)** screen.
+
+### 3.2 Book Selection
+
+The Book Selection acts as a folder and file browser.
 
 * **Navigate List:** Use **Left** (or **Volume Up**), or **Right** (or **Volume Down**) to move the selection cursor up 
   and down through folders and books.
 * **Open Selection:** Press **Confirm** to open a folder or read a selected book.
 
+### 3.3 Reading Mode
+
+See [Reading Mode](#4-reading-mode) below for more information.
+
+### 3.4 File Upload Screen
+
+The File Upload screen allows you to upload new e-books to the device. When you enter the screen, you'll be prompted with
+a WiFi selection dialog and then your X4 will start hosting a web server.
+
+See the [webserver docs](./docs/webserver.md) for more information on how to connect to the web server and upload files.
+
+### 3.5 Settings
+
+The Settings screen allows you to configure the device's behavior. There are a few settings you can adjust:
+- **Sleep Screen**: Which sleep screen to display when the device sleeps, options are:
+  - "Dark" (default) - The default dark sleep screen
+  - "Light" - The same default sleep screen, on a white background
+  - "Custom" - Custom images from the SD card, see [Sleep Screen](#36-sleep-screen) below for more information
+  - "Cover" - The book cover image (Note: this is experimental and may not work as expected)
+- **Status Bar**: Configure the status bar displayed while reading, options are:
+  - "None" - No status bar
+  - "No Progress" - Show status bar without reading progress
+  - "Full" - Show status bar with reading progress
+- **Extra Paragraph Spacing**: If enabled, vertical space will be added between paragraphs in the book, if disabled,
+  paragraphs will not have vertical space between them, but will have first word indentation.
+- **Short Power Button Click**: Whether to trigger the power button on a short press or a long press.
+- **Reading Orientation**: Set the screen orientation for reading, options are:
+  - "Portrait" (default) - Standard portrait orientation
+  - "Landscape CW" - Landscape, rotated clockwise
+  - "Inverted" - Portrait, upside down
+  - "Landscape CCW" - Landscape, rotated counter-clockwise
+- **Front Button Layout**: Configure the order of the bottom edge buttons, options are:
+  - "Bck, Cnfrm, Lft, Rght" (default) - Back, Confirm, Left, Right
+  - "Lft, Rght, Bck, Cnfrm" - Left, Right, Back, Confirm
+  - "Lft, Bck, Cnfrm, Rght" - Left, Back, Confirm, Right
+- **Side Button Layout**: Swap the order of the volume buttons from Previous/Next to Next/Previous. This change is only in effect when reading.
+- **Reader Font Family**: Choose the font used for reading, options are:
+  - "Bookerly" (default) - Amazon's reading font
+  - "Noto Sans" - Google's sans-serif font
+  - "Open Dyslexic" - Font designed for readers with dyslexia
+- **Reader Font Size**: Adjust the text size for reading, options are "Small", "Medium", "Large", or "X Large".
+- **Reader Line Spacing**: Adjust the spacing between lines, options are "Tight", "Normal", or "Wide".
+- **Check for updates**: Check for firmware updates over WiFi.
+
+### 3.6 Sleep Screen
+
+You can customize the sleep screen by placing custom images in specific locations on the SD card:
+
+- **Single Image:** Place a file named `sleep.bmp` in the root directory.
+- **Multiple Images:** Create a `sleep` directory in the root of the SD card and place any number of `.bmp` images
+  inside. If images are found in this directory, they will take priority over the `sleep.bmp` file, and one will be
+  randomly selected each time the device sleeps.
+
+> [!NOTE]
+> You'll need to set the **Sleep Screen** setting to **Custom** in order to use these images.
+
+> [!TIP]
+> For best results:
+> - Use uncompressed BMP files with 24-bit color depth
+> - Use a resolution of 480x800 pixels to match the device's screen resolution.
+
 ---
 
 ## 4. Reading Mode
@@ -54,8 +126,9 @@ Once you have opened a book, the button layout changes to facilitate reading.
 * **Previous Chapter:** Press and **hold** the **Left** (or **Volume Up**) button briefly, then release.
 
 ### System Navigation
-* **Return to Home:** Press **Back** to close the book and return to the Book Selection screen.
-* **Chapter Menu:** Press **Confirm** to open the Table of Contents/Chapter Selection screen.
+* **Return to Book Selection:** Press **Back** to close the book and return to the **[Book Selection](#32-book-selection)** screen.
+* **Return to Home:** Press and hold **Back** to close the book and return to the **[Home](#31-home-screen)** screen.
+* **Chapter Menu:** Press **Confirm** to open the **[Table of Contents/Chapter Selection](#5-chapter-selection-screen)**.
 
 ---
 
@@ -75,4 +148,3 @@ Please note that this firmware is currently in active development. The following
 are planned for future updates:
 
 * **Images:** Embedded images in e-books will not render.
-* **Text Formatting:** There are currently no settings to adjust font type, size, line spacing, or margins.

bin/clang-format-fix

@@ -1,3 +1,19 @@
 #!/bin/bash
 
-find src lib \( -name "*.c" -o -name "*.cpp" -o -name "*.h" -o -name "*.hpp" \) -exec clang-format -style=file -i {} +
+GIT_LS_FILES_FLAGS=""
+if [[ "$1" == "-g" ]]; then
+  GIT_LS_FILES_FLAGS="--modified"
+fi
+
+# --- Main Logic ---
+
+# Format all files (or only modified files if -g is passed)
+
+# Use 'git ls-files' to get a list of all files tracked by git:
+# --modified: files tracked by git that have been modified (staged or unstaged)
+# --exclude-standard: ignores files in .gitignore
+# Additionally exclude files in 'lib/EpdFont/builtinFonts/' as they are script-generated.
+git ls-files  --exclude-standard ${GIT_LS_FILES_FLAGS} \
+    | grep -E '\.(c|cpp|h|hpp)$' \
+    | grep -v -E '^lib/EpdFont/builtinFonts/' \
+    | xargs -r clang-format -style=file -i

docs/file-formats.md

@@ -0,0 +1,221 @@
+# File Formats
+
+## `book.bin`
+
+### Version 3
+
+ImHex Pattern:
+
+```c++
+import std.mem;
+import std.string;
+import std.core;
+
+// === Configuration ===
+#define EXPECTED_VERSION 3
+#define MAX_STRING_LENGTH 65535
+
+// === String Structure ===
+
+struct String {
+    u32 length [[hidden, comment("String byte length")]];
+    if (length > MAX_STRING_LENGTH) {
+        std::warning(std::format("Unusually large string length: {} bytes", length));
+    }
+    char data[length] [[comment("UTF-8 string data")]];
+} [[sealed, format("format_string"), comment("Length-prefixed UTF-8 string")]];
+
+fn format_string(String s) {
+    return s.data;
+};
+
+// === Metadata Structure ===
+
+struct Metadata {
+    String title [[comment("Book title")]];
+    String author [[comment("Book author")]];
+    String coverItemHref [[comment("Path to cover image")]];
+    String textReferenceHref [[comment("Path to guided first text reference")]];
+} [[comment("Book metadata information")]];
+
+// === Spine Entry Structure ===
+
+struct SpineEntry {
+    String href [[comment("Resource path")]];
+    u32 cumulativeSize [[comment("Cumulative size in bytes"), color("FF6B6B")]];
+    s16 tocIndex [[comment("Index into TOC (-1 if none)"), color("4ECDC4")]];
+} [[comment("Spine entry defining reading order")]];
+
+// === TOC Entry Structure ===
+
+struct TocEntry {
+    String title [[comment("Chapter/section title")]];
+    String href [[comment("Resource path")]];
+    String anchor [[comment("Fragment identifier")]];
+    u8 level [[comment("Nesting level (0-255)"), color("95E1D3")]];
+    s16 spineIndex [[comment("Index into spine (-1 if none)"), color("F38181")]];
+} [[comment("Table of contents entry")]];
+
+// === Book Bin Structure ===
+
+struct BookBin {
+    // Header
+    u8 version [[comment("Format version"), color("FFD93D")]];
+    
+    // Version validation
+    if (version != EXPECTED_VERSION) {
+        std::error(std::format("Unsupported version: {} (expected {})", version, EXPECTED_VERSION));
+    }
+    
+    u32 lutOffset [[comment("Offset to lookup tables"), color("6BCB77")]];
+    u16 spineCount [[comment("Number of spine entries"), color("4D96FF")]];
+    u16 tocCount [[comment("Number of TOC entries"), color("FF6B9D")]];
+    
+    // Metadata section
+    Metadata metadata [[comment("Book metadata")]];
+    
+    // Validate LUT offset alignment
+    u32 currentOffset = $;
+    if (currentOffset != lutOffset) {
+        std::warning(std::format("LUT offset mismatch: expected 0x{:X}, got 0x{:X}", lutOffset, currentOffset));
+    }
+    
+    // Lookup Tables
+    u32 spineLut[spineCount] [[comment("Spine entry offsets"), color("4D96FF")]];
+    u32 tocLut[tocCount] [[comment("TOC entry offsets"), color("FF6B9D")]];
+    
+    // Data Entries
+    SpineEntry spines[spineCount] [[comment("Spine entries (reading order)")]];
+    TocEntry toc[tocCount] [[comment("Table of contents entries")]];
+};
+
+// === File Parsing ===
+
+BookBin book @ 0x00;
+
+// Validate we've consumed the entire file
+u32 fileSize = std::mem::size();
+u32 parsedSize = $;
+
+if (parsedSize != fileSize) {
+    std::warning(std::format("Unparsed data detected: {} bytes remaining at offset 0x{:X}", fileSize - parsedSize, parsedSize));
+}
+```
+
+## `section.bin`
+
+### Version 8
+
+ImHex Pattern:
+
+```c++
+import std.mem;
+import std.string;
+import std.core;
+
+// === Configuration ===
+#define EXPECTED_VERSION 8
+#define MAX_STRING_LENGTH 65535
+
+// === String Structure ===
+
+struct String {
+    u32 length [[hidden, comment("String byte length")]];
+    if (length > MAX_STRING_LENGTH) {
+        std::warning(std::format("Unusually large string length: {} bytes", length));
+    }
+    char data[length] [[comment("UTF-8 string data")]];
+} [[sealed, format("format_string"), comment("Length-prefixed UTF-8 string")]];
+
+fn format_string(String s) {
+    return s.data;
+};
+
+// === Page Structure ===
+
+enum StorageType : u8 {
+    PageLine = 1
+};
+
+enum WordStyle : u8 {
+    REGULAR = 0,
+    BOLD = 1,
+    ITALIC = 2,
+    BOLD_ITALIC = 3
+};
+
+enum BlockStyle : u8 {
+    JUSTIFIED = 0,
+    LEFT_ALIGN = 1,
+    CENTER_ALIGN = 2,
+    RIGHT_ALIGN = 3,
+};
+
+struct PageLine {
+  s16 xPos;
+  s16 yPos;
+  u16 wordCount;
+  String words[wordCount];
+  u16 wordXPos[wordCount];
+  WordStyle wordStyle[wordCount];
+  BlockStyle blockStyle;
+};
+
+struct PageElement {
+    u8 pageElementType;
+    if (pageElementType == 1) {
+        PageLine pageLine [[inline]];
+    } else {
+        std::error(std::format("Unknown page element type: {}", pageElementType));
+    }
+};
+
+struct Page {
+    u16 elementCount;
+    PageElement elements[elementCount] [[inline]];
+};
+
+// === Section Bin Structure ===
+
+struct SectionBin {
+    // Header
+    u8 version [[comment("Format version"), color("FFD93D")]];
+    
+    // Version validation
+    if (version != EXPECTED_VERSION) {
+        std::error(std::format("Unsupported version: {} (expected {})", version, EXPECTED_VERSION));
+    }
+    
+    // Cache busting parameters
+    s32 fontId;
+    float lineCompression;
+    bool extraParagraphSpacing;
+    u16 viewportWidth;
+    u16 vieportHeight;
+    u16 pageCount;
+    u32 lutOffset;
+    
+    Page page[pageCount];
+    
+    // Validate LUT offset alignment
+    u32 currentOffset = $;
+    if (currentOffset != lutOffset) {
+        std::warning(std::format("LUT offset mismatch: expected 0x{:X}, got 0x{:X}", lutOffset, currentOffset));
+    }
+    
+    // Lookup Tables
+    u32 lut[pageCount];
+};
+
+// === File Parsing ===
+
+SectionBin book @ 0x00;
+
+// Validate we've consumed the entire file
+u32 fileSize = std::mem::size();
+u32 parsedSize = $;
+
+if (parsedSize != fileSize) {
+    std::warning(std::format("Unparsed data detected: {} bytes remaining at offset 0x{:X}", fileSize - parsedSize, parsedSize));
+}
+```

docs/webserver.md

@@ -0,0 +1,272 @@
+# Web Server Guide
+
+This guide explains how to connect your CrossPoint Reader to WiFi and use the built-in web server to upload EPUB files from your computer or phone.
+
+## Overview
+
+CrossPoint Reader includes a built-in web server that allows you to:
+
+- Upload EPUB files wirelessly from any device on the same WiFi network
+- Browse and manage files on your device's SD card
+- Create folders to organize your ebooks
+- Delete files and folders
+
+## Prerequisites
+
+- Your CrossPoint Reader device
+- A WiFi network
+- A computer, phone, or tablet connected to the **same WiFi network**
+
+---
+
+## Step 1: Accessing the WiFi Screen
+
+1. From the main menu or file browser, navigate to the **Settings** screen
+2. Select the **WiFi** option
+3. The device will automatically start scanning for available networks
+
+---
+
+## Step 2: Connecting to WiFi
+
+### Viewing Available Networks
+
+Once the scan completes, you'll see a list of available WiFi networks with the following indicators:
+
+- **Signal strength bars** (`||||`, `|||`, `||`, `|`) - Shows connection quality
+- **`*` symbol** - Indicates the network is password-protected (encrypted)
+- **`+` symbol** - Indicates you have previously saved credentials for this network
+
+<img src="./images/wifi/wifi_networks.jpeg" height="500">
+
+### Selecting a Network
+
+1. Use the **Left/Right** (or **Volume Up/Down**) buttons to navigate through the network list
+2. Press **Confirm** to select the highlighted network
+
+### Entering Password (for encrypted networks)
+
+If the network requires a password:
+
+1. An on-screen keyboard will appear
+2. Use the navigation buttons to select characters
+3. Press **Confirm** to enter each character
+4. When complete, select the **Done** option on the keyboard
+
+<img src="./images/wifi/wifi_password.jpeg" height="500">
+
+**Note:** If you've previously connected to this network, the saved password will be used automatically.
+
+### Connection Process
+
+The device will display "Connecting..." while establishing the connection. This typically takes 5-10 seconds.
+
+### Saving Credentials
+
+If this is a new network, you'll be prompted to save the password:
+
+- Select **Yes** to save credentials for automatic connection next time (NOTE: These are stored in plaintext on the device's SD card. Do not use this for sensitive networks.)
+- Select **No** to connect without saving
+
+---
+
+## Step 3: Connection Success
+
+Once connected, the screen will display:
+
+- **Network name** (SSID)
+- **IP Address** (e.g., `192.168.1.102`)
+- **Web server URL** (e.g., `http://192.168.1.102/`)
+
+<img src="./images/wifi/wifi_connected.jpeg" height="500">
+
+**Important:** Make note of the IP address - you'll need this to access the web interface from your computer or phone.
+
+---
+
+## Step 4: Accessing the Web Interface
+
+### From a Computer
+
+1. Ensure your computer is connected to the **same WiFi network** as your CrossPoint Reader
+2. Open any web browser (Chrome is recommended)
+3. Type the IP address shown on your device into the browser's address bar
+   - Example: `http://192.168.1.102/`
+4. Press Enter
+
+### From a Phone or Tablet
+
+1. Ensure your phone/tablet is connected to the **same WiFi network** as your CrossPoint Reader
+2. Open your mobile browser (Safari, Chrome, etc.)
+3. Type the IP address into the address bar
+   - Example: `http://192.168.1.102/`
+4. Tap Go
+
+---
+
+## Step 5: Using the Web Interface
+
+### Home Page
+
+The home page displays:
+
+- Device status and version information
+- WiFi connection status
+- Current IP address
+- Available memory
+
+Navigation links:
+
+- **Home** - Returns to the status page
+- **File Manager** - Access file management features
+
+<img src="./images/wifi/webserver_homepage.png" width="600">
+
+### File Manager
+
+Click **File Manager** to access file management features.
+
+#### Browsing Files
+
+- The file manager displays all files and folders on your SD card
+- **Folders** are highlighted in yellow with a 📁 icon
+- **EPUB files** are highlighted in green with a 📗 icon
+- Click on a folder name to navigate into it
+- Use the breadcrumb navigation at the top to go back to parent folders
+
+<img src="./images/wifi/webserver_files.png" width="600">
+
+#### Uploading EPUB Files
+
+1. Click the **+ Add** button in the top-right corner
+2. Select **Upload eBook** from the dropdown menu
+3. Click **Choose File** and select an `.epub` file from your device
+4. Click **Upload**
+5. A progress bar will show the upload status
+6. The page will automatically refresh when the upload is complete
+
+**Note:** Only `.epub` files are accepted. Other file types will be rejected.
+
+<img src="./images/wifi/webserver_upload.png" width="600">
+
+#### Creating Folders
+
+1. Click the **+ Add** button in the top-right corner
+2. Select **New Folder** from the dropdown menu
+3. Enter a folder name (letters, numbers, underscores, and hyphens only)
+4. Click **Create Folder**
+
+This is useful for organizing your ebooks by genre, author, or series.
+
+#### Deleting Files and Folders
+
+1. Click the **🗑️** (trash) icon next to any file or folder
+2. Confirm the deletion in the popup dialog
+3. Click **Delete** to permanently remove the item
+
+**Warning:** Deletion is permanent and cannot be undone!
+
+**Note:** Folders must be empty before they can be deleted.
+
+---
+
+## Troubleshooting
+
+### Cannot See the Device on the Network
+
+**Problem:** Browser shows "Cannot connect" or "Site can't be reached"
+
+**Solutions:**
+
+1. Verify both devices are on the **same WiFi network**
+   - Check your computer/phone WiFi settings
+   - Confirm the CrossPoint Reader shows "Connected" status
+2. Double-check the IP address
+   - Make sure you typed it correctly
+   - Include `http://` at the beginning
+3. Try disabling VPN if you're using one
+4. Some networks have "client isolation" enabled - check with your network administrator
+
+### Connection Drops or Times Out
+
+**Problem:** WiFi connection is unstable
+
+**Solutions:**
+
+1. Move closer to the WiFi router
+2. Check signal strength on the device (should be at least `||` or better)
+3. Avoid interference from other devices
+4. Try a different WiFi network if available
+
+### Upload Fails
+
+**Problem:** File upload doesn't complete or shows an error
+
+**Solutions:**
+
+1. Ensure the file is a valid `.epub` file
+2. Check that the SD card has enough free space
+3. Try uploading a smaller file first to test
+4. Refresh the browser page and try again
+
+### Saved Password Not Working
+
+**Problem:** Device fails to connect with saved credentials
+
+**Solutions:**
+
+1. When connection fails, you'll be prompted to "Forget Network"
+2. Select **Yes** to remove the saved password
+3. Reconnect and enter the password again
+4. Choose to save the new password
+
+---
+
+## Security Notes
+
+- The web server runs on port 80 (standard HTTP)
+- **No authentication is required** - anyone on the same network can access the interface
+- The web server is only accessible while the WiFi screen shows "Connected"
+- The web server automatically stops when you exit the WiFi screen
+- For security, only use on trusted private networks
+
+---
+
+## Technical Details
+
+- **Supported WiFi:** 2.4GHz networks (802.11 b/g/n)
+- **Web Server Port:** 80 (HTTP)
+- **Maximum Upload Size:** Limited by available SD card space
+- **Supported File Format:** `.epub` only
+- **Browser Compatibility:** All modern browsers (Chrome, Firefox, Safari, Edge)
+
+---
+
+## Tips and Best Practices
+
+1. **Organize with folders** - Create folders before uploading to keep your library organized
+2. **Check signal strength** - Stronger signals (`|||` or `||||`) provide faster, more reliable uploads
+3. **Upload multiple files** - You can upload files one at a time; the page refreshes after each upload
+4. **Use descriptive names** - Name your folders clearly (e.g., "SciFi", "Mystery", "Non-Fiction")
+5. **Keep credentials saved** - Save your WiFi password for quick reconnection in the future
+6. **Exit when done** - Press **Back** to exit the WiFi screen and save battery
+
+---
+
+## Exiting WiFi Mode
+
+When you're finished uploading files:
+
+1. Press the **Back** button on your CrossPoint Reader
+2. The web server will automatically stop
+3. WiFi will disconnect to conserve battery
+4. You'll return to the previous screen
+
+Your uploaded files will be immediately available in the file browser!
+
+---
+
+## Related Documentation
+
+- [User Guide](../USER_GUIDE.md) - General device operation
+- [README](../README.md) - Project overview and features

lib/EpdFont/EpdFont.cpp

@@ -2,8 +2,7 @@
 
 #include <Utf8.h>
 
-inline int min(const int a, const int b) { return a < b ? a : b; }
-inline int max(const int a, const int b) { return a < b ? b : a; }
+#include <algorithm>
 
 void EpdFont::getTextBounds(const char* string, const int startX, const int startY, int* minX, int* minY, int* maxX,
                             int* maxY) const {
@@ -32,10 +31,10 @@ void EpdFont::getTextBounds(const char* string, const int startX, const int star
       continue;
     }
 
-    *minX = min(*minX, cursorX + glyph->left);
-    *maxX = max(*maxX, cursorX + glyph->left + glyph->width);
-    *minY = min(*minY, cursorY + glyph->top - glyph->height);
-    *maxY = max(*maxY, cursorY + glyph->top);
+    *minX = std::min(*minX, cursorX + glyph->left);
+    *maxX = std::max(*maxX, cursorX + glyph->left + glyph->width);
+    *minY = std::min(*minY, cursorY + glyph->top - glyph->height);
+    *maxY = std::max(*maxY, cursorY + glyph->top);
     cursorX += glyph->advanceX;
   }
 }
@@ -59,14 +58,28 @@ bool EpdFont::hasPrintableChars(const char* string) const {
 
 const EpdGlyph* EpdFont::getGlyph(const uint32_t cp) const {
   const EpdUnicodeInterval* intervals = data->intervals;
-  for (int i = 0; i < data->intervalCount; i++) {
-    const EpdUnicodeInterval* interval = &intervals[i];
-    if (cp >= interval->first && cp <= interval->last) {
+  const int count = data->intervalCount;
+
+  if (count == 0) return nullptr;
+
+  // Binary search for O(log n) lookup instead of O(n)
+  // Critical for Korean fonts with many unicode intervals
+  int left = 0;
+  int right = count - 1;
+
+  while (left <= right) {
+    const int mid = left + (right - left) / 2;
+    const EpdUnicodeInterval* interval = &intervals[mid];
+
+    if (cp < interval->first) {
+      right = mid - 1;
+    } else if (cp > interval->last) {
+      left = mid + 1;
+    } else {
+      // Found: cp >= interval->first && cp <= interval->last
       return &data->glyph[interval->offset + (cp - interval->first)];
     }
-    if (cp < interval->first) {
-      return nullptr;
-    }
   }
+
   return nullptr;
 }

lib/EpdFont/EpdFontFamily.cpp

@@ -1,6 +1,6 @@
 #include "EpdFontFamily.h"
 
-const EpdFont* EpdFontFamily::getFont(const EpdFontStyle style) const {
+const EpdFont* EpdFontFamily::getFont(const Style style) const {
   if (style == BOLD && bold) {
     return bold;
   }
@@ -22,16 +22,16 @@ const EpdFont* EpdFontFamily::getFont(const EpdFontStyle style) const {
   return regular;
 }
 
-void EpdFontFamily::getTextDimensions(const char* string, int* w, int* h, const EpdFontStyle style) const {
+void EpdFontFamily::getTextDimensions(const char* string, int* w, int* h, const Style style) const {
   getFont(style)->getTextDimensions(string, w, h);
 }
 
-bool EpdFontFamily::hasPrintableChars(const char* string, const EpdFontStyle style) const {
+bool EpdFontFamily::hasPrintableChars(const char* string, const Style style) const {
   return getFont(style)->hasPrintableChars(string);
 }
 
-const EpdFontData* EpdFontFamily::getData(const EpdFontStyle style) const { return getFont(style)->data; }
+const EpdFontData* EpdFontFamily::getData(const Style style) const { return getFont(style)->data; }
 
-const EpdGlyph* EpdFontFamily::getGlyph(const uint32_t cp, const EpdFontStyle style) const {
+const EpdGlyph* EpdFontFamily::getGlyph(const uint32_t cp, const Style style) const {
   return getFont(style)->getGlyph(cp);
 };

lib/EpdFont/EpdFontFamily.h

@@ -1,24 +1,24 @@
 #pragma once
 #include "EpdFont.h"
 
-enum EpdFontStyle { REGULAR, BOLD, ITALIC, BOLD_ITALIC };
-
 class EpdFontFamily {
+ public:
+  enum Style : uint8_t { REGULAR = 0, BOLD = 1, ITALIC = 2, BOLD_ITALIC = 3 };
+
+  explicit EpdFontFamily(const EpdFont* regular, const EpdFont* bold = nullptr, const EpdFont* italic = nullptr,
+                         const EpdFont* boldItalic = nullptr)
+      : regular(regular), bold(bold), italic(italic), boldItalic(boldItalic) {}
+  ~EpdFontFamily() = default;
+  void getTextDimensions(const char* string, int* w, int* h, Style style = REGULAR) const;
+  bool hasPrintableChars(const char* string, Style style = REGULAR) const;
+  const EpdFontData* getData(Style style = REGULAR) const;
+  const EpdGlyph* getGlyph(uint32_t cp, Style style = REGULAR) const;
+
+ private:
   const EpdFont* regular;
   const EpdFont* bold;
   const EpdFont* italic;
   const EpdFont* boldItalic;
 
-  const EpdFont* getFont(EpdFontStyle style) const;
-
- public:
-  explicit EpdFontFamily(const EpdFont* regular, const EpdFont* bold = nullptr, const EpdFont* italic = nullptr,
-                         const EpdFont* boldItalic = nullptr)
-      : regular(regular), bold(bold), italic(italic), boldItalic(boldItalic) {}
-  ~EpdFontFamily() = default;
-  void getTextDimensions(const char* string, int* w, int* h, EpdFontStyle style = REGULAR) const;
-  bool hasPrintableChars(const char* string, EpdFontStyle style = REGULAR) const;
-
-  const EpdFontData* getData(EpdFontStyle style = REGULAR) const;
-  const EpdGlyph* getGlyph(uint32_t cp, EpdFontStyle style = REGULAR) const;
+  const EpdFont* getFont(Style style) const;
 };

lib/EpdFont/builtinFonts/all.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <builtinFonts/bookerly_12_bold.h>
+#include <builtinFonts/bookerly_12_bolditalic.h>
+#include <builtinFonts/bookerly_12_italic.h>
+#include <builtinFonts/bookerly_12_regular.h>
+#include <builtinFonts/bookerly_14_bold.h>
+#include <builtinFonts/bookerly_14_bolditalic.h>
+#include <builtinFonts/bookerly_14_italic.h>
+#include <builtinFonts/bookerly_14_regular.h>
+#include <builtinFonts/bookerly_16_bold.h>
+#include <builtinFonts/bookerly_16_bolditalic.h>
+#include <builtinFonts/bookerly_16_italic.h>
+#include <builtinFonts/bookerly_16_regular.h>
+#include <builtinFonts/bookerly_18_bold.h>
+#include <builtinFonts/bookerly_18_bolditalic.h>
+#include <builtinFonts/bookerly_18_italic.h>
+#include <builtinFonts/bookerly_18_regular.h>
+#include <builtinFonts/notosans_8_regular.h>
+#include <builtinFonts/notosans_12_bold.h>
+#include <builtinFonts/notosans_12_bolditalic.h>
+#include <builtinFonts/notosans_12_italic.h>
+#include <builtinFonts/notosans_12_regular.h>
+#include <builtinFonts/notosans_14_bold.h>
+#include <builtinFonts/notosans_14_bolditalic.h>
+#include <builtinFonts/notosans_14_italic.h>
+#include <builtinFonts/notosans_14_regular.h>
+#include <builtinFonts/notosans_16_bold.h>
+#include <builtinFonts/notosans_16_bolditalic.h>
+#include <builtinFonts/notosans_16_italic.h>
+#include <builtinFonts/notosans_16_regular.h>
+#include <builtinFonts/notosans_18_bold.h>
+#include <builtinFonts/notosans_18_bolditalic.h>
+#include <builtinFonts/notosans_18_italic.h>
+#include <builtinFonts/notosans_18_regular.h>
+#include <builtinFonts/opendyslexic_10_bold.h>
+#include <builtinFonts/opendyslexic_10_bolditalic.h>
+#include <builtinFonts/opendyslexic_10_italic.h>
+#include <builtinFonts/opendyslexic_10_regular.h>
+#include <builtinFonts/opendyslexic_12_bold.h>
+#include <builtinFonts/opendyslexic_12_bolditalic.h>
+#include <builtinFonts/opendyslexic_12_italic.h>
+#include <builtinFonts/opendyslexic_12_regular.h>
+#include <builtinFonts/opendyslexic_14_bold.h>
+#include <builtinFonts/opendyslexic_14_bolditalic.h>
+#include <builtinFonts/opendyslexic_14_italic.h>
+#include <builtinFonts/opendyslexic_14_regular.h>
+#include <builtinFonts/opendyslexic_8_bold.h>
+#include <builtinFonts/opendyslexic_8_bolditalic.h>
+#include <builtinFonts/opendyslexic_8_italic.h>
+#include <builtinFonts/opendyslexic_8_regular.h>
+#include <builtinFonts/ubuntu_10_bold.h>
+#include <builtinFonts/ubuntu_10_regular.h>
+#include <builtinFonts/ubuntu_12_bold.h>
+#include <builtinFonts/ubuntu_12_regular.h>