diff --git a/.config/rubocop/config.yml b/.config/rubocop/config.yml
index 39b33dd..77af493 100644
--- a/.config/rubocop/config.yml
+++ b/.config/rubocop/config.yml
@@ -4,3 +4,6 @@ inherit_gem:
 Metrics/ParameterLists:
   Exclude:
     - lib/trmnl/api/requester.rb
+Style/IpAddresses:
+  Exclude:
+    - spec/lib/trmnl/api/types_spec.rb
diff --git a/lib/trmnl/api/types.rb b/lib/trmnl/api/types.rb
new file mode 100644
index 0000000..1c926ff
--- /dev/null
+++ b/lib/trmnl/api/types.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require "dry/types"
+require "ipaddr"
+
+module TRMNL
+  module API
+    # A collection of custom types.
+    module Types
+      include Dry.Types(default: :strict)
+
+      CSSVariables = Dry::Types["array"].of(
+        Dry::Types["array"].constrained(filled: true, size: 2).of(Dry::Types["coercible.string"])
+      )
+
+      IPAddress = Constructor IPAddr
+    end
+  end
+end
diff --git a/spec/lib/trmnl/api/types_spec.rb b/spec/lib/trmnl/api/types_spec.rb
new file mode 100644
index 0000000..768621f
--- /dev/null
+++ b/spec/lib/trmnl/api/types_spec.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe TRMNL::API::Types do
+  describe "CSSVariables" do
+    subject(:type) { described_class::CSSVariables }
+
+    it "answers primitive" do
+      expect(type.primitive).to eq(Array)
+    end
+
+    it "answers array of CSS variables when valid" do
+      variables = [%w[--screen-w 1040px], %w[--screen-h 780px]]
+      expect(type.call(variables)).to eq(variables)
+    end
+
+    it "answers array of coerced strings when valid" do
+      expect(type.call([[1, 2]])).to eq([%w[1 2]])
+    end
+
+    it "fails with empty constraint error" do
+      expectation = proc { type.call [[]] }
+
+      expect(&expectation).to raise_error(
+        Dry::Types::ConstraintError,
+        "[] violates constraints (filled?([]) AND size?(2, []) failed)"
+      )
+    end
+
+    it "fails with size constraint error" do
+      expectation = proc { type.call [[1, 2, 3]] }
+
+      expect(&expectation).to raise_error(
+        Dry::Types::ConstraintError,
+        "[1, 2, 3] violates constraints (size?(2, [1, 2, 3]) failed)"
+      )
+    end
+  end
+
+  describe "IPAddress" do
+    subject(:type) { described_class::IPAddress }
+
+    it "answers primitive" do
+      expect(type.primitive).to eq(IPAddr)
+    end
+
+    it "answers Version 4.0.0 address" do
+      expect(type.call("10.10.1.5")).to eq(IPAddr.new("10.10.1.5"))
+    end
+
+    it "answers Version 6.0.0 address" do
+      expect(type.call("111:a111:111:d1:0:1:111e:1111")).to eq(
+        IPAddr.new("111:a111:111:d1:0:1:111e:1111")
+      )
+    end
+  end
+end