diff --git a/Sources/PlaydateKit/Display/Display.swift b/Sources/PlaydateKit/Display/Display.swift
index e1381db..6e76406 100644
--- a/Sources/PlaydateKit/Display/Display.swift
+++ b/Sources/PlaydateKit/Display/Display.swift
@@ -4,6 +4,7 @@ internal import CPlaydate
 public enum Display {}
 
 extension Display {
+    /// The cached `playdate->display` C API table.
     private static var api: UnsafePointer<playdate_display> { Playdate.displayAPI.unsafelyUnwrapped }
 
     /// The display width in pixels, taking the current scale into account.
diff --git a/Sources/PlaydateKit/File/Enumerations/SeekOrigin.swift b/Sources/PlaydateKit/File/Enumerations/SeekOrigin.swift
index eb46596..0b3fe94 100644
--- a/Sources/PlaydateKit/File/Enumerations/SeekOrigin.swift
+++ b/Sources/PlaydateKit/File/Enumerations/SeekOrigin.swift
@@ -1,8 +1,11 @@
 extension File {
     /// The origin used by `Handle.seek(to:from:)`.
     public enum SeekOrigin: Int32, Sendable {
+        /// Relative to the beginning of the file.
         case start = 0
+        /// Relative to the current offset.
         case current = 1
+        /// Relative to the end of the file.
         case end = 2
     }
 }
diff --git a/Sources/PlaydateKit/File/File.swift b/Sources/PlaydateKit/File/File.swift
index 41b4f19..b6a6380 100644
--- a/Sources/PlaydateKit/File/File.swift
+++ b/Sources/PlaydateKit/File/File.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->file` C API table.
 var fileAPI: UnsafePointer<playdate_file> { Playdate.fileAPI.unsafelyUnwrapped }
 
 /// The most recent file system error as a thrown error.
@@ -8,6 +9,9 @@ func lastFileError() -> PlaydateError {
 }
 
 /// The file API: access to the game's Data directory and pdx contents.
+///
+/// Paths are relative to the game's Data directory (read/write) or the
+/// game's pdx (read-only), depending on the mode used to open them.
 public enum File {}
 
 extension File {
diff --git a/Sources/PlaydateKit/File/Structures/Stat.swift b/Sources/PlaydateKit/File/Structures/Stat.swift
index 3e484e4..58ad59a 100644
--- a/Sources/PlaydateKit/File/Structures/Stat.swift
+++ b/Sources/PlaydateKit/File/Structures/Stat.swift
@@ -1,8 +1,11 @@
 extension File {
     /// Information about a file or directory, mirroring `FileStat`.
     public struct Stat: Sendable {
+        /// Whether the path is a directory.
         public let isDirectory: Bool
+        /// The file's size, in bytes.
         public let size: UInt32
+        /// The time the file was last modified.
         public let modified: System.DateTime
     }
 }
diff --git a/Sources/PlaydateKit/Graphics/Classes/Bitmap.swift b/Sources/PlaydateKit/Graphics/Classes/Bitmap.swift
index fab07b4..e40a8a8 100644
--- a/Sources/PlaydateKit/Graphics/Classes/Bitmap.swift
+++ b/Sources/PlaydateKit/Graphics/Classes/Bitmap.swift
@@ -39,6 +39,7 @@ extension Graphics {
 
         // MARK: Properties
 
+        /// The bitmap's dimensions, row stride, and raw storage.
         public var data: Data {
             var width: Int32 = 0, height: Int32 = 0, rowBytes: Int32 = 0
             var mask: UnsafeMutablePointer<UInt8>?
@@ -61,7 +62,9 @@ extension Graphics {
             return size
         }
 
+        /// The bitmap's width, in pixels.
         public var width: Int { size.width }
+        /// The bitmap's height, in pixels.
         public var height: Int { size.height }
 
         /// The color of the pixel at (x, y).
@@ -84,6 +87,7 @@ extension Graphics {
             color.withLCDColor { gfx.pointee.clearBitmap.unsafelyUnwrapped(pointer, $0) }
         }
 
+        /// Returns a new copy of the bitmap.
         public func copy() -> Bitmap {
             Bitmap(pointer: gfx.pointee.copyBitmap.unsafelyUnwrapped(pointer).unsafelyUnwrapped, isOwned: true)
         }
diff --git a/Sources/PlaydateKit/Graphics/Classes/BitmapTable.swift b/Sources/PlaydateKit/Graphics/Classes/BitmapTable.swift
index cc7c73e..792f4a2 100644
--- a/Sources/PlaydateKit/Graphics/Classes/BitmapTable.swift
+++ b/Sources/PlaydateKit/Graphics/Classes/BitmapTable.swift
@@ -52,6 +52,7 @@ extension Graphics {
             return (Int(count), Int(width))
         }
 
+        /// The number of bitmaps in the table.
         public var count: Int { info.count }
     }
 }
diff --git a/Sources/PlaydateKit/Graphics/Classes/StreamPlayer.swift b/Sources/PlaydateKit/Graphics/Classes/StreamPlayer.swift
index 007e6ae..46bf11e 100644
--- a/Sources/PlaydateKit/Graphics/Classes/StreamPlayer.swift
+++ b/Sources/PlaydateKit/Graphics/Classes/StreamPlayer.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->graphics->videostream` C API table.
 private var streamAPI: UnsafePointer<playdate_videostream> { Playdate.videoStreamAPI.unsafelyUnwrapped }
 
 extension Graphics {
diff --git a/Sources/PlaydateKit/Graphics/Classes/TileMap.swift b/Sources/PlaydateKit/Graphics/Classes/TileMap.swift
index ef04c4a..daa1003 100644
--- a/Sources/PlaydateKit/Graphics/Classes/TileMap.swift
+++ b/Sources/PlaydateKit/Graphics/Classes/TileMap.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->graphics->tilemap` C API table.
 private var tilemapAPI: UnsafePointer<playdate_tilemap> { Playdate.tilemapAPI.unsafelyUnwrapped }
 
 extension Graphics {
diff --git a/Sources/PlaydateKit/Graphics/Classes/VideoPlayer.swift b/Sources/PlaydateKit/Graphics/Classes/VideoPlayer.swift
index 48896a7..919c6ca 100644
--- a/Sources/PlaydateKit/Graphics/Classes/VideoPlayer.swift
+++ b/Sources/PlaydateKit/Graphics/Classes/VideoPlayer.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->graphics->video` C API table.
 private var videoAPI: UnsafePointer<playdate_video> { Playdate.videoAPI.unsafelyUnwrapped }
 
 extension Graphics {
diff --git a/Sources/PlaydateKit/Graphics/Enumerations/Color.swift b/Sources/PlaydateKit/Graphics/Enumerations/Color.swift
index 5512494..798ddd6 100644
--- a/Sources/PlaydateKit/Graphics/Enumerations/Color.swift
+++ b/Sources/PlaydateKit/Graphics/Enumerations/Color.swift
@@ -3,10 +3,15 @@ internal import CPlaydate
 extension Graphics {
     /// A drawing color: solid or an 8×8 pattern.
     public enum Color: Sendable {
+        /// Solid black.
         case black
+        /// Solid white.
         case white
+        /// Transparent; leaves the destination unchanged.
         case clear
+        /// Inverts the destination pixels.
         case xor
+        /// An 8×8 two-color pattern.
         case pattern(Pattern)
 
         /// Materializes the `LCDColor` for the duration of `body`. Pattern
diff --git a/Sources/PlaydateKit/Graphics/Enumerations/DrawMode.swift b/Sources/PlaydateKit/Graphics/Enumerations/DrawMode.swift
index 92dfe4b..6f951ef 100644
--- a/Sources/PlaydateKit/Graphics/Enumerations/DrawMode.swift
+++ b/Sources/PlaydateKit/Graphics/Enumerations/DrawMode.swift
@@ -3,13 +3,21 @@ internal import CPlaydate
 extension Graphics {
     /// How source pixels combine with the destination when drawing.
     public enum DrawMode: UInt32, Sendable {
+        /// Source pixels replace the destination.
         case copy = 0
+        /// White source pixels are treated as transparent.
         case whiteTransparent = 1
+        /// Black source pixels are treated as transparent.
         case blackTransparent = 2
+        /// Opaque source pixels draw white.
         case fillWhite = 3
+        /// Opaque source pixels draw black.
         case fillBlack = 4
+        /// Source pixels are XORed with the destination.
         case xor = 5
+        /// The inverse of `xor`.
         case nxor = 6
+        /// Source pixels draw inverted.
         case inverted = 7
 
         init(_ mode: LCDBitmapDrawMode) { self = DrawMode(rawValue: UInt32(mode.rawValue)) ?? .copy }
diff --git a/Sources/PlaydateKit/Graphics/Graphics.swift b/Sources/PlaydateKit/Graphics/Graphics.swift
index c361738..f1fa54a 100644
--- a/Sources/PlaydateKit/Graphics/Graphics.swift
+++ b/Sources/PlaydateKit/Graphics/Graphics.swift
@@ -3,6 +3,7 @@ internal import CPlaydate
 /// The graphics API: drawing, bitmaps, fonts, tilemaps, and video.
 public enum Graphics {}
 
+/// The cached `playdate->graphics` C API table.
 var gfx: UnsafePointer<playdate_graphics> { Playdate.graphicsAPI.unsafelyUnwrapped }
 
 extension Graphics {
@@ -50,10 +51,12 @@ extension Graphics {
         gfx.pointee.setScreenClipRect.unsafelyUnwrapped(Int32(x), Int32(y), Int32(width), Int32(height))
     }
 
+    /// Clears the current clip rect.
     public static func clearClipRect() {
         gfx.pointee.clearClipRect.unsafelyUnwrapped()
     }
 
+    /// Sets the end cap style used by subsequent line drawing.
     public static func setLineCapStyle(_ style: LineCapStyle) {
         gfx.pointee.setLineCapStyle.unsafelyUnwrapped(style.cValue)
     }
@@ -71,18 +74,21 @@ extension Graphics {
         gfx.pointee.pushContext.unsafelyUnwrapped(target?.pointer)
     }
 
+    /// Pops the top drawing context off the stack.
     public static func popContext() {
         gfx.pointee.popContext.unsafelyUnwrapped()
     }
 
     // MARK: - Shapes
 
+    /// Draws a line from (x1, y1) to (x2, y2) with the given stroke width.
     public static func drawLine(x1: Int, y1: Int, x2: Int, y2: Int, width: Int, color: Color) {
         color.withLCDColor {
             gfx.pointee.drawLine.unsafelyUnwrapped(Int32(x1), Int32(y1), Int32(x2), Int32(y2), Int32(width), $0)
         }
     }
 
+    /// Fills the triangle with vertices (x1, y1), (x2, y2), and (x3, y3).
     public static func fillTriangle(x1: Int, y1: Int, x2: Int, y2: Int, x3: Int, y3: Int, color: Color) {
         color.withLCDColor {
             gfx.pointee.fillTriangle.unsafelyUnwrapped(Int32(x1), Int32(y1), Int32(x2), Int32(y2),
@@ -90,18 +96,22 @@ extension Graphics {
         }
     }
 
+    /// Draws the outline of a rectangle, stroked inside its frame.
     public static func drawRect(x: Int, y: Int, width: Int, height: Int, color: Color) {
         color.withLCDColor {
             gfx.pointee.drawRect.unsafelyUnwrapped(Int32(x), Int32(y), Int32(width), Int32(height), $0)
         }
     }
 
+    /// Fills the rectangle with `color`.
     public static func fillRect(x: Int, y: Int, width: Int, height: Int, color: Color) {
         color.withLCDColor {
             gfx.pointee.fillRect.unsafelyUnwrapped(Int32(x), Int32(y), Int32(width), Int32(height), $0)
         }
     }
 
+    /// Draws the outline of a rectangle with rounded corners, stroked with
+    /// `lineWidth`.
     public static func drawRoundRect(x: Int, y: Int, width: Int, height: Int, radius: Int,
                                      lineWidth: Int, color: Color) {
         color.withLCDColor {
@@ -110,6 +120,7 @@ extension Graphics {
         }
     }
 
+    /// Fills a rectangle with rounded corners.
     public static func fillRoundRect(x: Int, y: Int, width: Int, height: Int, radius: Int, color: Color) {
         color.withLCDColor {
             gfx.pointee.fillRoundRect.unsafelyUnwrapped(Int32(x), Int32(y), Int32(width), Int32(height),
@@ -127,6 +138,8 @@ extension Graphics {
         }
     }
 
+    /// Fills an ellipse inside the rect. If the angles differ, fills the
+    /// wedge from `startAngle` to `endAngle` (clockwise degrees, 0 at top).
     public static func fillEllipse(x: Int, y: Int, width: Int, height: Int,
                                    startAngle: Float = 0, endAngle: Float = 0, color: Color) {
         color.withLCDColor {
@@ -202,6 +215,7 @@ extension Graphics {
         gfx.pointee.setTextTracking.unsafelyUnwrapped(Int32(tracking))
     }
 
+    /// The extra space currently added between letters, in pixels.
     public static var textTracking: Int {
         Int(gfx.pointee.getTextTracking.unsafelyUnwrapped())
     }
diff --git a/Sources/PlaydateKit/Graphics/Structures/Bitmap.Data.swift b/Sources/PlaydateKit/Graphics/Structures/Bitmap.Data.swift
index 9d99caf..7efc480 100644
--- a/Sources/PlaydateKit/Graphics/Structures/Bitmap.Data.swift
+++ b/Sources/PlaydateKit/Graphics/Structures/Bitmap.Data.swift
@@ -2,10 +2,17 @@ extension Graphics.Bitmap {
     /// The bitmap's dimensions, row stride, and raw pixel/mask storage.
     /// The pointers are owned by the bitmap.
     public struct Data {
+        /// The bitmap's width, in pixels.
         public let width: Int
+        /// The bitmap's height, in pixels.
         public let height: Int
+        /// The stride of one row of pixel data, in bytes.
         public let rowBytes: Int
+        /// The bitmap's mask data, or `nil` if it has no mask. One bit per
+        /// pixel; rows are `rowBytes` wide.
         public let mask: UnsafeMutablePointer<UInt8>?
+        /// The bitmap's pixel data. One bit per pixel; rows are `rowBytes`
+        /// wide.
         public let data: UnsafeMutablePointer<UInt8>?
     }
 }
diff --git a/Sources/PlaydateKit/Graphics/Structures/Graphics.Rect.swift b/Sources/PlaydateKit/Graphics/Structures/Graphics.Rect.swift
index 3d6d75b..1748ddf 100644
--- a/Sources/PlaydateKit/Graphics/Structures/Graphics.Rect.swift
+++ b/Sources/PlaydateKit/Graphics/Structures/Graphics.Rect.swift
@@ -9,6 +9,8 @@ extension Graphics {
         public var top: Int
         public var bottom: Int
 
+        /// Creates a rect from its edges. `right` and `bottom` are not
+        /// inclusive.
         public init(left: Int, right: Int, top: Int, bottom: Int) {
             self.left = left
             self.right = right
@@ -16,6 +18,7 @@ extension Graphics {
             self.bottom = bottom
         }
 
+        /// Creates a rect from an origin and size.
         public init(x: Int, y: Int, width: Int, height: Int) {
             self.init(left: x, right: x + width, top: y, bottom: y + height)
         }
@@ -30,6 +33,7 @@ extension Graphics {
                     top: Int32(top), bottom: Int32(bottom))
         }
 
+        /// Returns the rect offset by (dx, dy).
         public func translated(dx: Int, dy: Int) -> Rect {
             Rect(left: left + dx, right: right + dx, top: top + dy, bottom: bottom + dy)
         }
diff --git a/Sources/PlaydateKit/Graphics/Structures/Pattern.swift b/Sources/PlaydateKit/Graphics/Structures/Pattern.swift
index 84ddf49..32b6815 100644
--- a/Sources/PlaydateKit/Graphics/Structures/Pattern.swift
+++ b/Sources/PlaydateKit/Graphics/Structures/Pattern.swift
@@ -1,9 +1,12 @@
 extension Graphics {
     /// An 8×8 two-color pattern: 8 rows of image data followed by 8 rows of mask.
     public struct Pattern: Sendable {
+        /// The pattern's 8 rows of image data followed by 8 rows of mask,
+        /// one byte per row.
         public var bytes: (UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8,
                            UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8)
 
+        /// Creates a pattern from 8 rows of image data and 8 rows of mask.
         public init(bytes: (UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8,
                             UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8, UInt8)) {
             self.bytes = bytes
diff --git a/Sources/PlaydateKit/JSON/Classes/Encoder.swift b/Sources/PlaydateKit/JSON/Classes/Encoder.swift
index 2aef1e5..505bcbb 100644
--- a/Sources/PlaydateKit/JSON/Classes/Encoder.swift
+++ b/Sources/PlaydateKit/JSON/Classes/Encoder.swift
@@ -22,6 +22,7 @@ extension JSON {
         /// The JSON produced so far.
         public var json: String { output.text }
 
+        /// Starts a JSON array.
         public func startArray() {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.startArray.unsafelyUnwrapped($0) }
         }
@@ -31,10 +32,12 @@ extension JSON {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.addArrayMember.unsafelyUnwrapped($0) }
         }
 
+        /// Ends the current array.
         public func endArray() {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.endArray.unsafelyUnwrapped($0) }
         }
 
+        /// Starts a JSON object.
         public func startTable() {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.startTable.unsafelyUnwrapped($0) }
         }
@@ -48,28 +51,34 @@ extension JSON {
             }
         }
 
+        /// Ends the current object.
         public func endTable() {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.endTable.unsafelyUnwrapped($0) }
         }
 
+        /// Writes a `null` value.
         public func writeNull() {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.writeNull.unsafelyUnwrapped($0) }
         }
 
+        /// Writes a boolean value.
         public func writeBool(_ value: Bool) {
             withUnsafeMutablePointer(to: &encoder) {
                 (value ? $0.pointee.writeTrue : $0.pointee.writeFalse).unsafelyUnwrapped($0)
             }
         }
 
+        /// Writes an integer value.
         public func writeInt(_ value: Int) {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.writeInt.unsafelyUnwrapped($0, Int32(value)) }
         }
 
+        /// Writes a floating-point value.
         public func writeDouble(_ value: Double) {
             withUnsafeMutablePointer(to: &encoder) { $0.pointee.writeDouble.unsafelyUnwrapped($0, value) }
         }
 
+        /// Writes a string value.
         public func writeString(_ value: String) {
             value.withPlaydateCString { cString in
                 withUnsafeMutablePointer(to: &encoder) {
diff --git a/Sources/PlaydateKit/JSON/Enumerations/Value.swift b/Sources/PlaydateKit/JSON/Enumerations/Value.swift
index 7938136..10bed5e 100644
--- a/Sources/PlaydateKit/JSON/Enumerations/Value.swift
+++ b/Sources/PlaydateKit/JSON/Enumerations/Value.swift
@@ -1,12 +1,19 @@
 extension JSON {
     /// A decoded JSON value.
     public indirect enum Value {
+        /// A JSON `null`.
         case null
+        /// A JSON `true` or `false`.
         case bool(Bool)
+        /// A JSON number without a fractional part.
         case int(Int)
+        /// A JSON number with a fractional part.
         case float(Float)
+        /// A JSON string.
         case string(String)
+        /// A JSON array.
         case array([Value])
+        /// A JSON object.
         case table([String: Value])
     }
 }
diff --git a/Sources/PlaydateKit/JSON/JSON.swift b/Sources/PlaydateKit/JSON/JSON.swift
index c24323a..9b3a42f 100644
--- a/Sources/PlaydateKit/JSON/JSON.swift
+++ b/Sources/PlaydateKit/JSON/JSON.swift
@@ -1,8 +1,13 @@
 internal import CPlaydate
 
+/// The cached `playdate->json` C API table.
 var jsonAPI: UnsafePointer<playdate_json> { Playdate.jsonAPI.unsafelyUnwrapped }
 
 /// The JSON API: decoding to and encoding from a `Value` tree.
+///
+/// The C decoder is callback-based; this wrapper drives it to build a
+/// complete `Value` tree. The encoder is exposed both as a streaming
+/// `Encoder` and as a one-shot `encode(_:)` of a `Value`.
 public enum JSON {}
 
 extension JSON {
diff --git a/Sources/PlaydateKit/Lua/Enumerations/ClassValue.swift b/Sources/PlaydateKit/Lua/Enumerations/ClassValue.swift
index 2db98f7..5c97985 100644
--- a/Sources/PlaydateKit/Lua/Enumerations/ClassValue.swift
+++ b/Sources/PlaydateKit/Lua/Enumerations/ClassValue.swift
@@ -1,8 +1,11 @@
 extension Lua {
     /// A constant published on a registered class.
     public enum ClassValue {
+        /// An integer constant.
         case int(name: String, value: UInt32)
+        /// A floating-point constant.
         case float(name: String, value: Float)
+        /// A string constant.
         case string(name: String, value: String)
     }
 }
diff --git a/Sources/PlaydateKit/Lua/Lua.swift b/Sources/PlaydateKit/Lua/Lua.swift
index 7cdcc49..7f73b57 100644
--- a/Sources/PlaydateKit/Lua/Lua.swift
+++ b/Sources/PlaydateKit/Lua/Lua.swift
@@ -1,9 +1,14 @@
 internal import CPlaydate
 
+/// The cached `playdate->lua` C API table.
 var luaAPI: UnsafePointer<playdate_lua> { Playdate.luaAPI.unsafelyUnwrapped }
 
 /// The Lua bridge: registering C functions and classes, and exchanging
 /// values with Lua code.
+///
+/// Lua callbacks are C function pointers without userdata, so functions
+/// registered here must be `@convention(c)` (the `CFunction` typealias),
+/// not capturing closures.
 public enum Lua {}
 
 extension Lua {
@@ -168,26 +173,33 @@ extension Lua {
 
     // MARK: - Return values
 
+    /// Pushes nil onto the stack.
     public static func pushNil() {
         luaAPI.pointee.pushNil.unsafelyUnwrapped()
     }
 
+    /// Pushes a boolean onto the stack.
     public static func push(_ value: Bool) {
         luaAPI.pointee.pushBool.unsafelyUnwrapped(value ? 1 : 0)
     }
 
+    /// Pushes an integer onto the stack.
     public static func push(_ value: Int) {
         luaAPI.pointee.pushInt.unsafelyUnwrapped(Int32(value))
     }
 
+    /// Pushes a float onto the stack.
     public static func push(_ value: Float) {
         luaAPI.pointee.pushFloat.unsafelyUnwrapped(value)
     }
 
+    /// Pushes a string onto the stack.
     public static func push(_ value: String) {
         value.withPlaydateCString { luaAPI.pointee.pushString.unsafelyUnwrapped($0) }
     }
 
+    /// Pushes raw bytes (which may contain embedded zeros) onto the stack
+    /// as a Lua string.
     public static func push(bytes: [UInt8]) {
         bytes.withUnsafeBytes { buffer in
             luaAPI.pointee.pushBytes.unsafelyUnwrapped(
@@ -195,10 +207,12 @@ extension Lua {
         }
     }
 
+    /// Pushes a bitmap onto the stack.
     public static func push(_ bitmap: Graphics.Bitmap) {
         luaAPI.pointee.pushBitmap.unsafelyUnwrapped(bitmap.pointer)
     }
 
+    /// Pushes a sprite onto the stack.
     public static func push(_ sprite: Sprite) {
         luaAPI.pointee.pushSprite.unsafelyUnwrapped(sprite.pointer)
     }
diff --git a/Sources/PlaydateKit/Lua/Structures/UDObject.swift b/Sources/PlaydateKit/Lua/Structures/UDObject.swift
index afd73a7..0a3ec0b 100644
--- a/Sources/PlaydateKit/Lua/Structures/UDObject.swift
+++ b/Sources/PlaydateKit/Lua/Structures/UDObject.swift
@@ -11,6 +11,8 @@ extension Lua {
             UDObject(pointer: luaAPI.pointee.retainObject.unsafelyUnwrapped(pointer).unsafelyUnwrapped)
         }
 
+        /// Balances a `retain()`, allowing the object to be
+        /// garbage-collected again.
         public func release() {
             luaAPI.pointee.releaseObject.unsafelyUnwrapped(pointer)
         }
diff --git a/Sources/PlaydateKit/Network/Classes/HTTPConnection.swift b/Sources/PlaydateKit/Network/Classes/HTTPConnection.swift
index cf31564..1281d7c 100644
--- a/Sources/PlaydateKit/Network/Classes/HTTPConnection.swift
+++ b/Sources/PlaydateKit/Network/Classes/HTTPConnection.swift
@@ -1,9 +1,14 @@
 internal import CPlaydate
 
+/// The cached `playdate->network->http` C API table.
 private var httpAPI: UnsafePointer<playdate_http> { Playdate.httpAPI.unsafelyUnwrapped }
 
 extension Network {
     /// An HTTP connection to a server. Wraps `HTTPConnection`.
+    ///
+    /// The binding stores a back-reference to each wrapper in the
+    /// underlying object's userdata slot so callbacks can recover the
+    /// wrapper; the C userdata slot is therefore reserved by the binding.
     public final class HTTPConnection {
         let pointer: OpaquePointer
 
diff --git a/Sources/PlaydateKit/Network/Classes/TCPConnection.swift b/Sources/PlaydateKit/Network/Classes/TCPConnection.swift
index 999c1c5..21e122b 100644
--- a/Sources/PlaydateKit/Network/Classes/TCPConnection.swift
+++ b/Sources/PlaydateKit/Network/Classes/TCPConnection.swift
@@ -1,9 +1,14 @@
 internal import CPlaydate
 
+/// The cached `playdate->network->tcp` C API table.
 private var tcpAPI: UnsafePointer<playdate_tcp> { Playdate.tcpAPI.unsafelyUnwrapped }
 
 extension Network {
     /// A TCP connection to a server. Wraps `TCPConnection`.
+    ///
+    /// The binding stores a back-reference to each wrapper in the
+    /// underlying object's userdata slot so callbacks can recover the
+    /// wrapper; the C userdata slot is therefore reserved by the binding.
     public final class TCPConnection {
         let pointer: OpaquePointer
 
diff --git a/Sources/PlaydateKit/Network/Enumerations/NetError.swift b/Sources/PlaydateKit/Network/Enumerations/NetError.swift
index 6307d90..f80137e 100644
--- a/Sources/PlaydateKit/Network/Enumerations/NetError.swift
+++ b/Sources/PlaydateKit/Network/Enumerations/NetError.swift
@@ -21,8 +21,11 @@ extension Network {
         case notConnectedToAP = -16
         case notImplemented = -17
         case connectionClosed = -18
+        /// An error code not covered by `PDNetErr`.
         case unknown = 1
 
+        /// Creates an error from the C code, or `.unknown` for
+        /// unrecognized codes.
         init(_ error: PDNetErr) {
             self = NetError(rawValue: Int32(error.rawValue)) ?? .unknown
         }
diff --git a/Sources/PlaydateKit/Network/Network.swift b/Sources/PlaydateKit/Network/Network.swift
index 2318e0c..7f67483 100644
--- a/Sources/PlaydateKit/Network/Network.swift
+++ b/Sources/PlaydateKit/Network/Network.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->network` C API table.
 private var networkAPI: UnsafePointer<playdate_network> { Playdate.networkAPI.unsafelyUnwrapped }
 
 /// The network API: wifi status, HTTP, and TCP.
@@ -18,6 +19,7 @@ extension Network {
         error == NET_OK ? nil : NetError(error)
     }
 
+    /// The device's current wifi status.
     public static var status: WifiStatus {
         WifiStatus(rawValue: UInt32(networkAPI.pointee.getStatus.unsafelyUnwrapped().rawValue)) ?? .notConnected
     }
diff --git a/Sources/PlaydateKit/Playdate/Enumerations/AccessReply.swift b/Sources/PlaydateKit/Playdate/Enumerations/AccessReply.swift
index 7eca6bd..57b2778 100644
--- a/Sources/PlaydateKit/Playdate/Enumerations/AccessReply.swift
+++ b/Sources/PlaydateKit/Playdate/Enumerations/AccessReply.swift
@@ -1,6 +1,10 @@
 /// The user's answer to a permission request (microphone, network).
 public enum AccessReply: UInt32, Sendable {
+    /// The user has not answered yet; the request's completion delivers
+    /// the answer later.
     case ask = 0
+    /// The user has already denied access; the completion is not called.
     case deny = 1
+    /// The user has already granted access; the completion is not called.
     case allow = 2
 }
diff --git a/Sources/PlaydateKit/Playdate/Enumerations/SystemEvent.swift b/Sources/PlaydateKit/Playdate/Enumerations/SystemEvent.swift
index a74bcbd..71b689c 100644
--- a/Sources/PlaydateKit/Playdate/Enumerations/SystemEvent.swift
+++ b/Sources/PlaydateKit/Playdate/Enumerations/SystemEvent.swift
@@ -3,19 +3,34 @@ public import CPlaydate
 /// A Swift view of `PDSystemEvent` with the key code folded into the
 /// key events.
 public enum SystemEvent {
+    /// Sent once at startup, before the first update.
     case initialize
+    /// Sent when the Lua runtime is ready, for registering custom
+    /// functions and classes.
     case initializeLua
+    /// The device was locked.
     case lock
+    /// The device was unlocked.
     case unlock
+    /// The game was paused (e.g. the system menu opened).
     case pause
+    /// The game resumed after a pause.
     case resume
+    /// The game is about to be terminated.
     case terminate
+    /// A simulator key was pressed.
     case keyPressed(keyCode: UInt32)
+    /// A simulator key was released.
     case keyReleased(keyCode: UInt32)
+    /// The device is about to power down because the battery is low.
     case lowPower
+    /// A Mirror session started.
     case mirrorStarted
+    /// A Mirror session ended.
     case mirrorEnded
 
+    /// Creates an event from the C event and its argument, or `nil` for
+    /// events unknown to this binding.
     public init?(event: PDSystemEvent, argument: UInt32) {
         switch event {
         case kEventInit: self = .initialize
diff --git a/Sources/PlaydateKit/Playdate/Playdate.swift b/Sources/PlaydateKit/Playdate/Playdate.swift
index 4d18dd3..9d528a7 100644
--- a/Sources/PlaydateKit/Playdate/Playdate.swift
+++ b/Sources/PlaydateKit/Playdate/Playdate.swift
@@ -1,8 +1,12 @@
 public import CPlaydate
 
-/// The raw C API bootstrap. Everything else in this module (System,
-/// Graphics, Sprite, Sound, ...) lives at the top level of the `PlaydateKit`
-/// module and requires `initialize(with:)` to have been called first.
+/// The raw C API bootstrap.
+///
+/// The C API is delivered as a `PlaydateAPI` struct of function pointers
+/// that the firmware hands to the game's `eventHandler` entry point. Call
+/// `initialize(with:)` from that entry point before using any other API in
+/// this module. Everything else (System, Graphics, Sprite, Sound, ...)
+/// lives at the top level of the `PlaydateKit` module.
 public enum Playdate {
     /// The raw C API. Populated by `initialize(with:)`.
     ///
diff --git a/Sources/PlaydateKit/Playdate/Structures/PlaydateError.swift b/Sources/PlaydateKit/Playdate/Structures/PlaydateError.swift
index d1a720a..6692e22 100644
--- a/Sources/PlaydateKit/Playdate/Structures/PlaydateError.swift
+++ b/Sources/PlaydateKit/Playdate/Structures/PlaydateError.swift
@@ -1,11 +1,15 @@
 /// An error reported by the Playdate OS.
 public struct PlaydateError: Swift.Error, Sendable {
+    /// The message reported by the OS, or a description of the failure.
     public let message: String
 
+    /// Creates an error with the given message.
     init(message: String) {
         self.message = message
     }
 
+    /// Creates an error by copying an OS-provided C string; a nil pointer
+    /// produces "unknown error".
     init(cString: UnsafePointer<CChar>?) {
         self.init(message: String(playdateCString: cString) ?? "unknown error")
     }
diff --git a/Sources/PlaydateKit/Scoreboards/Scoreboards.swift b/Sources/PlaydateKit/Scoreboards/Scoreboards.swift
index 8ebdbdb..8026588 100644
--- a/Sources/PlaydateKit/Scoreboards/Scoreboards.swift
+++ b/Sources/PlaydateKit/Scoreboards/Scoreboards.swift
@@ -1,8 +1,13 @@
 internal import CPlaydate
 
+/// The cached `playdate->scoreboards` C API table.
 var scoreboardsAPI: UnsafePointer<playdate_scoreboards> { Playdate.scoreboardsAPI.unsafelyUnwrapped }
 
 /// The scoreboards API for games with online leaderboards.
+///
+/// The C callbacks carry no userdata, so one completion per operation kind
+/// is tracked at a time; starting a second request of the same kind before
+/// the first completes replaces the stored completion.
 public enum Scoreboards {}
 
 extension Scoreboards {
diff --git a/Sources/PlaydateKit/Scoreboards/Structures/Board.swift b/Sources/PlaydateKit/Scoreboards/Structures/Board.swift
index c1461b9..e602429 100644
--- a/Sources/PlaydateKit/Scoreboards/Structures/Board.swift
+++ b/Sources/PlaydateKit/Scoreboards/Structures/Board.swift
@@ -3,7 +3,9 @@ internal import CPlaydate
 extension Scoreboards {
     /// A board belonging to the game.
     public struct Board {
+        /// The board's identifier, used in the other scoreboard calls.
         public let boardID: String
+        /// The board's display name.
         public let name: String
 
         init(_ board: PDBoard) {
diff --git a/Sources/PlaydateKit/Scoreboards/Structures/BoardsList.swift b/Sources/PlaydateKit/Scoreboards/Structures/BoardsList.swift
index 3ac0515..46f7027 100644
--- a/Sources/PlaydateKit/Scoreboards/Structures/BoardsList.swift
+++ b/Sources/PlaydateKit/Scoreboards/Structures/BoardsList.swift
@@ -3,7 +3,9 @@ internal import CPlaydate
 extension Scoreboards {
     /// The game's boards.
     public struct BoardsList {
+        /// When the list was last updated, in seconds since the epoch.
         public let lastUpdated: UInt32
+        /// The game's boards.
         public let boards: [Board]
 
         init(_ list: PDBoardsList) {
diff --git a/Sources/PlaydateKit/Scoreboards/Structures/Score.swift b/Sources/PlaydateKit/Scoreboards/Structures/Score.swift
index 43c6f06..cd2533d 100644
--- a/Sources/PlaydateKit/Scoreboards/Structures/Score.swift
+++ b/Sources/PlaydateKit/Scoreboards/Structures/Score.swift
@@ -3,9 +3,13 @@ internal import CPlaydate
 extension Scoreboards {
     /// A score on a board.
     public struct Score {
+        /// The score's position on the board, starting at 1.
         public let rank: UInt32
+        /// The score's value.
         public let value: UInt32
+        /// The name of the player who posted the score.
         public let player: String
+        /// The board the score belongs to, when known.
         public let boardID: String?
 
         init(_ score: PDScore) {
diff --git a/Sources/PlaydateKit/Scoreboards/Structures/ScoresList.swift b/Sources/PlaydateKit/Scoreboards/Structures/ScoresList.swift
index 0045e07..c957e84 100644
--- a/Sources/PlaydateKit/Scoreboards/Structures/ScoresList.swift
+++ b/Sources/PlaydateKit/Scoreboards/Structures/ScoresList.swift
@@ -3,10 +3,15 @@ internal import CPlaydate
 extension Scoreboards {
     /// The scores on a board.
     public struct ScoresList {
+        /// The board the scores belong to.
         public let boardID: String
+        /// When the list was last updated, in seconds since the epoch.
         public let lastUpdated: UInt32
+        /// Whether the current player's score is included in the list.
         public let playerIncluded: Bool
+        /// The maximum number of scores the list can hold.
         public let limit: UInt32
+        /// The scores, ordered by rank.
         public let scores: [Score]
 
         init(_ list: PDScoresList) {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/BitCrusher.swift b/Sources/PlaydateKit/Sound/Effect/Classes/BitCrusher.swift
index bb14230..c3f29a1 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/BitCrusher.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/BitCrusher.swift
@@ -28,6 +28,7 @@ extension Sound {
             BitCrusher.api.pointee.setDepth.unsafelyUnwrapped(pointer, depth)
         }
 
+        /// Modulates the crush depth.
         public var depthModulator: SignalValue? {
             get { SignalValue.wrap(BitCrusher.api.pointee.getDepthModulator.unsafelyUnwrapped(pointer)) }
             set {
@@ -41,6 +42,7 @@ extension Sound {
             BitCrusher.api.pointee.setDownsampling.unsafelyUnwrapped(pointer, downsampling)
         }
 
+        /// Modulates the downsampling amount.
         public var downsamplingModulator: SignalValue? {
             get { SignalValue.wrap(BitCrusher.api.pointee.getDownsamplingModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/DelayLineTap.swift b/Sources/PlaydateKit/Sound/Effect/Classes/DelayLineTap.swift
index b272e04..290ffc3 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/DelayLineTap.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/DelayLineTap.swift
@@ -24,6 +24,7 @@ extension Sound {
             DelayLineTap.api.pointee.setTapDelay.unsafelyUnwrapped(pointer, Int32(frames))
         }
 
+        /// Modulates the tap's delay.
         public var delayModulator: SignalValue? {
             get { SignalValue.wrap(DelayLineTap.api.pointee.getTapDelayModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/Effect.swift b/Sources/PlaydateKit/Sound/Effect/Classes/Effect.swift
index 3df534d..a76e784 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/Effect.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/Effect.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->sound->effect` C API table.
 private var effectAPI: UnsafePointer<playdate_sound_effect> { Playdate.effectAPI.unsafelyUnwrapped }
 
 extension Sound {
@@ -48,6 +49,7 @@ extension Sound {
             effectAPI.pointee.setMix.unsafelyUnwrapped(pointer, level)
         }
 
+        /// Modulates the wet/dry mix.
         public var mixModulator: SignalValue? {
             get { SignalValue.wrap(effectAPI.pointee.getMixModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/OnePoleFilter.swift b/Sources/PlaydateKit/Sound/Effect/Classes/OnePoleFilter.swift
index 11187b4..2228e7a 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/OnePoleFilter.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/OnePoleFilter.swift
@@ -24,6 +24,7 @@ extension Sound {
             OnePoleFilter.api.pointee.setParameter.unsafelyUnwrapped(pointer, parameter)
         }
 
+        /// Modulates the filter's cutoff parameter.
         public var parameterModulator: SignalValue? {
             get { SignalValue.wrap(OnePoleFilter.api.pointee.getParameterModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/Overdrive.swift b/Sources/PlaydateKit/Sound/Effect/Classes/Overdrive.swift
index c887166..3997c48 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/Overdrive.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/Overdrive.swift
@@ -28,6 +28,7 @@ extension Sound {
             Overdrive.api.pointee.setLimit.unsafelyUnwrapped(pointer, limit)
         }
 
+        /// Modulates the clipping limit.
         public var limitModulator: SignalValue? {
             get { SignalValue.wrap(Overdrive.api.pointee.getLimitModulator.unsafelyUnwrapped(pointer)) }
             set {
@@ -41,6 +42,7 @@ extension Sound {
             Overdrive.api.pointee.setOffset.unsafelyUnwrapped(pointer, offset)
         }
 
+        /// Modulates the DC offset.
         public var offsetModulator: SignalValue? {
             get { SignalValue.wrap(Overdrive.api.pointee.getOffsetModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/RingModulator.swift b/Sources/PlaydateKit/Sound/Effect/Classes/RingModulator.swift
index dcaac75..39bf760 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/RingModulator.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/RingModulator.swift
@@ -23,6 +23,7 @@ extension Sound {
             RingModulator.api.pointee.setFrequency.unsafelyUnwrapped(pointer, frequency)
         }
 
+        /// Modulates the modulation frequency.
         public var frequencyModulator: SignalValue? {
             get { SignalValue.wrap(RingModulator.api.pointee.getFrequencyModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Classes/TwoPoleFilter.swift b/Sources/PlaydateKit/Sound/Effect/Classes/TwoPoleFilter.swift
index 4216e97..0f7dfca 100644
--- a/Sources/PlaydateKit/Sound/Effect/Classes/TwoPoleFilter.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Classes/TwoPoleFilter.swift
@@ -29,6 +29,7 @@ extension Sound {
             TwoPoleFilter.api.pointee.setFrequency.unsafelyUnwrapped(pointer, frequency)
         }
 
+        /// Modulates the filter's frequency.
         public var frequencyModulator: SignalValue? {
             get { SignalValue.wrap(TwoPoleFilter.api.pointee.getFrequencyModulator.unsafelyUnwrapped(pointer)) }
             set {
@@ -46,6 +47,7 @@ extension Sound {
             TwoPoleFilter.api.pointee.setResonance.unsafelyUnwrapped(pointer, resonance)
         }
 
+        /// Modulates the filter's resonance.
         public var resonanceModulator: SignalValue? {
             get { SignalValue.wrap(TwoPoleFilter.api.pointee.getResonanceModulator.unsafelyUnwrapped(pointer)) }
             set {
diff --git a/Sources/PlaydateKit/Sound/Effect/Enumerations/TwoPoleFilter.Kind.swift b/Sources/PlaydateKit/Sound/Effect/Enumerations/TwoPoleFilter.Kind.swift
index 96b4362..166b57a 100644
--- a/Sources/PlaydateKit/Sound/Effect/Enumerations/TwoPoleFilter.Kind.swift
+++ b/Sources/PlaydateKit/Sound/Effect/Enumerations/TwoPoleFilter.Kind.swift
@@ -1,11 +1,13 @@
 internal import CPlaydate
 
 extension Sound.TwoPoleFilter {
+    /// The filter's response type.
     public enum Kind: UInt32, Sendable {
         case lowPass = 0
         case highPass = 1
         case bandPass = 2
         case notch = 3
+        /// A parametric EQ filter.
         case peq = 4
         case lowShelf = 5
         case highShelf = 6
diff --git a/Sources/PlaydateKit/Sound/Enumerations/Format.swift b/Sources/PlaydateKit/Sound/Enumerations/Format.swift
index 787dcb3..50b3d5e 100644
--- a/Sources/PlaydateKit/Sound/Enumerations/Format.swift
+++ b/Sources/PlaydateKit/Sound/Enumerations/Format.swift
@@ -13,8 +13,11 @@ extension Sound {
         init(_ format: SoundFormat) { self = Format(rawValue: UInt32(format.rawValue)) ?? .mono16bit }
         var cValue: SoundFormat { SoundFormat(SoundFormat.RawValue(rawValue)) }
 
+        /// Whether the format has two channels.
         public var isStereo: Bool { rawValue & 1 != 0 }
+        /// Whether samples are 16-bit (rather than 8-bit or ADPCM).
         public var is16bit: Bool { rawValue >= 2 && rawValue < 4 }
+        /// The size of one sample frame, in bytes.
         public var bytesPerFrame: Int { Int(SoundFormat_bytesPerFrame(cValue)) }
     }
 }
diff --git a/Sources/PlaydateKit/Sound/Enumerations/MicSource.swift b/Sources/PlaydateKit/Sound/Enumerations/MicSource.swift
index b6c03c9..55e6e94 100644
--- a/Sources/PlaydateKit/Sound/Enumerations/MicSource.swift
+++ b/Sources/PlaydateKit/Sound/Enumerations/MicSource.swift
@@ -1,8 +1,12 @@
 extension Sound {
     /// The microphone used when recording.
     public enum MicSource: UInt32, Sendable {
+        /// Use the headset microphone if one is connected, otherwise the
+        /// built-in microphone.
         case autodetect = 0
+        /// Always use the built-in microphone.
         case internalMic = 1
+        /// Always use the headset microphone.
         case headset = 2
     }
 }
diff --git a/Sources/PlaydateKit/Sound/Signal/Classes/ControlSignal.swift b/Sources/PlaydateKit/Sound/Signal/Classes/ControlSignal.swift
index 27b58b1..8d7c077 100644
--- a/Sources/PlaydateKit/Sound/Signal/Classes/ControlSignal.swift
+++ b/Sources/PlaydateKit/Sound/Signal/Classes/ControlSignal.swift
@@ -21,6 +21,7 @@ extension Sound {
             }
         }
 
+        /// Removes all events from the signal's timeline.
         public func clearEvents() {
             ControlSignal.api.pointee.clearEvents.unsafelyUnwrapped(pointer)
         }
@@ -32,6 +33,7 @@ extension Sound {
                                                          interpolate ? 1 : 0)
         }
 
+        /// Removes the event at `step`, if any.
         public func removeEvent(step: Int) {
             ControlSignal.api.pointee.removeEvent.unsafelyUnwrapped(pointer, Int32(step))
         }
diff --git a/Sources/PlaydateKit/Sound/Signal/Classes/Envelope.swift b/Sources/PlaydateKit/Sound/Signal/Classes/Envelope.swift
index 09be698..53d0bf3 100644
--- a/Sources/PlaydateKit/Sound/Signal/Classes/Envelope.swift
+++ b/Sources/PlaydateKit/Sound/Signal/Classes/Envelope.swift
@@ -22,18 +22,22 @@ extension Sound {
             }
         }
 
+        /// The attack time, in seconds.
         public func setAttack(_ attack: Float) {
             Envelope.api.pointee.setAttack.unsafelyUnwrapped(pointer, attack)
         }
 
+        /// The decay time, in seconds.
         public func setDecay(_ decay: Float) {
             Envelope.api.pointee.setDecay.unsafelyUnwrapped(pointer, decay)
         }
 
+        /// The sustain level, 0...1.
         public func setSustain(_ sustain: Float) {
             Envelope.api.pointee.setSustain.unsafelyUnwrapped(pointer, sustain)
         }
 
+        /// The release time, in seconds.
         public func setRelease(_ release: Float) {
             Envelope.api.pointee.setRelease.unsafelyUnwrapped(pointer, release)
         }
@@ -66,6 +70,7 @@ extension Sound {
             Envelope.api.pointee.setRateScaling.unsafelyUnwrapped(pointer, scaling, start, end)
         }
 
+        /// The envelope's current value.
         public var value: Float {
             Envelope.api.pointee.getValue.unsafelyUnwrapped(pointer)
         }
diff --git a/Sources/PlaydateKit/Sound/Signal/Classes/LFO.swift b/Sources/PlaydateKit/Sound/Signal/Classes/LFO.swift
index eaeddba..61f170e 100644
--- a/Sources/PlaydateKit/Sound/Signal/Classes/LFO.swift
+++ b/Sources/PlaydateKit/Sound/Signal/Classes/LFO.swift
@@ -89,6 +89,7 @@ extension Sound {
             LFO.api.pointee.setRandomSeed.unsafelyUnwrapped(pointer, seed)
         }
 
+        /// The LFO's current value.
         public var value: Float {
             LFO.api.pointee.getValue.unsafelyUnwrapped(pointer)
         }
diff --git a/Sources/PlaydateKit/Sound/Sound.swift b/Sources/PlaydateKit/Sound/Sound.swift
index 1dc274b..658af3d 100644
--- a/Sources/PlaydateKit/Sound/Sound.swift
+++ b/Sources/PlaydateKit/Sound/Sound.swift
@@ -1,5 +1,6 @@
 internal import CPlaydate
 
+/// The cached `playdate->sound` C API table.
 var snd: UnsafePointer<playdate_sound> { Playdate.soundAPI.unsafelyUnwrapped }
 
 /// The sound API: channels, players, synths, sequences, and effects.
diff --git a/Sources/PlaydateKit/Sound/Source/Classes/FilePlayer.swift b/Sources/PlaydateKit/Sound/Source/Classes/FilePlayer.swift
index 5bc36a0..b41dd42 100644
--- a/Sources/PlaydateKit/Sound/Source/Classes/FilePlayer.swift
+++ b/Sources/PlaydateKit/Sound/Source/Classes/FilePlayer.swift
@@ -52,10 +52,12 @@ extension Sound {
             FilePlayer.api.pointee.play.unsafelyUnwrapped(pointer, Int32(repeatCount)) != 0
         }
 
+        /// Pauses playback.
         public func pause() {
             FilePlayer.api.pointee.pause.unsafelyUnwrapped(pointer)
         }
 
+        /// Stops playback.
         public func stop() {
             FilePlayer.api.pointee.stop.unsafelyUnwrapped(pointer)
         }
diff --git a/Sources/PlaydateKit/Sound/Source/Classes/SamplePlayer.swift b/Sources/PlaydateKit/Sound/Source/Classes/SamplePlayer.swift
index 2a4a758..305a3e4 100644
--- a/Sources/PlaydateKit/Sound/Source/Classes/SamplePlayer.swift
+++ b/Sources/PlaydateKit/Sound/Source/Classes/SamplePlayer.swift
@@ -46,10 +46,12 @@ extension Sound {
             SamplePlayer.api.pointee.play.unsafelyUnwrapped(pointer, Int32(repeatCount), rate) != 0
         }
 
+        /// Stops playback.
         public func stop() {
             SamplePlayer.api.pointee.stop.unsafelyUnwrapped(pointer)
         }
 
+        /// Pauses or resumes playback.
         public func setPaused(_ paused: Bool) {
             SamplePlayer.api.pointee.setPaused.unsafelyUnwrapped(pointer, paused ? 1 : 0)
         }
diff --git a/Sources/PlaydateKit/Sound/Synth/Classes/Instrument.swift b/Sources/PlaydateKit/Sound/Synth/Classes/Instrument.swift
index e63ee14..b940bcc 100644
--- a/Sources/PlaydateKit/Sound/Synth/Classes/Instrument.swift
+++ b/Sources/PlaydateKit/Sound/Synth/Classes/Instrument.swift
@@ -72,10 +72,13 @@ extension Sound {
             Instrument.api.pointee.setPitchBend.unsafelyUnwrapped(pointer, bend)
         }
 
+        /// The range of `setPitchBend(_:)`, in half-steps.
         public func setPitchBendRange(halfSteps: Float) {
             Instrument.api.pointee.setPitchBendRange.unsafelyUnwrapped(pointer, halfSteps)
         }
 
+        /// Transposes played notes by `halfSteps` (fractional values
+        /// allowed).
         public func setTranspose(halfSteps: Float) {
             Instrument.api.pointee.setTranspose.unsafelyUnwrapped(pointer, halfSteps)
         }
@@ -85,20 +88,24 @@ extension Sound {
             Instrument.api.pointee.noteOff.unsafelyUnwrapped(pointer, note, when)
         }
 
+        /// Releases every playing voice at time `when` (0 = now).
         public func allNotesOff(when: UInt32 = 0) {
             Instrument.api.pointee.allNotesOff.unsafelyUnwrapped(pointer, when)
         }
 
+        /// Sets the volume of the left and right channels, 0...1.
         public func setVolume(left: Float, right: Float) {
             Instrument.api.pointee.setVolume.unsafelyUnwrapped(pointer, left, right)
         }
 
+        /// The volume of the left and right channels.
         public var volume: (left: Float, right: Float) {
             var left: Float = 0, right: Float = 0
             Instrument.api.pointee.getVolume.unsafelyUnwrapped(pointer, &left, &right)
             return (left, right)
         }
 
+        /// The number of voices currently playing.
         public var activeVoiceCount: Int {
             Int(Instrument.api.pointee.activeVoiceCount.unsafelyUnwrapped(pointer))
         }
diff --git a/Sources/PlaydateKit/Sound/Synth/Classes/Sequence.swift b/Sources/PlaydateKit/Sound/Synth/Classes/Sequence.swift
index f29e57f..b21779d 100644
--- a/Sources/PlaydateKit/Sound/Synth/Classes/Sequence.swift
+++ b/Sources/PlaydateKit/Sound/Synth/Classes/Sequence.swift
@@ -47,10 +47,12 @@ extension Sound {
             }
         }
 
+        /// Stops playback.
         public func stop() {
             Sequence.api.pointee.stop.unsafelyUnwrapped(pointer)
         }
 
+        /// Whether the sequence is playing.
         public var isPlaying: Bool {
             Sequence.api.pointee.isPlaying.unsafelyUnwrapped(pointer) != 0
         }
diff --git a/Sources/PlaydateKit/Sound/Synth/Classes/SequenceTrack.swift b/Sources/PlaydateKit/Sound/Synth/Classes/SequenceTrack.swift
index 07826e0..b08ff88 100644
--- a/Sources/PlaydateKit/Sound/Synth/Classes/SequenceTrack.swift
+++ b/Sources/PlaydateKit/Sound/Synth/Classes/SequenceTrack.swift
@@ -45,10 +45,12 @@ extension Sound {
             SequenceTrack.api.pointee.addNoteEvent.unsafelyUnwrapped(pointer, step, length, note, velocity)
         }
 
+        /// Removes the note at `step`, if any.
         public func removeNote(step: UInt32, note: MIDINote) {
             SequenceTrack.api.pointee.removeNoteEvent.unsafelyUnwrapped(pointer, step, note)
         }
 
+        /// Removes all notes from the track.
         public func clearNotes() {
             SequenceTrack.api.pointee.clearNotes.unsafelyUnwrapped(pointer)
         }
@@ -94,6 +96,7 @@ extension Sound {
             return ControlSignal(pointer: signal, isOwned: false)
         }
 
+        /// Removes all control signal events from the track.
         public func clearControlEvents() {
             SequenceTrack.api.pointee.clearControlEvents.unsafelyUnwrapped(pointer)
         }
@@ -103,10 +106,12 @@ extension Sound {
             Int(SequenceTrack.api.pointee.getPolyphony.unsafelyUnwrapped(pointer))
         }
 
+        /// The number of notes currently playing.
         public var activeVoiceCount: Int {
             Int(SequenceTrack.api.pointee.activeVoiceCount.unsafelyUnwrapped(pointer))
         }
 
+        /// Mutes or unmutes the track.
         public func setMuted(_ muted: Bool) {
             SequenceTrack.api.pointee.setMuted.unsafelyUnwrapped(pointer, muted ? 1 : 0)
         }
diff --git a/Sources/PlaydateKit/Sound/Synth/Classes/Synth.swift b/Sources/PlaydateKit/Sound/Synth/Classes/Synth.swift
index 2c3ef26..5b3b6d8 100644
--- a/Sources/PlaydateKit/Sound/Synth/Classes/Synth.swift
+++ b/Sources/PlaydateKit/Sound/Synth/Classes/Synth.swift
@@ -108,18 +108,22 @@ extension Sound {
 
         // MARK: Envelope
 
+        /// The envelope's attack time, in seconds.
         public func setAttackTime(_ attack: Float) {
             Synth.api.pointee.setAttackTime.unsafelyUnwrapped(pointer, attack)
         }
 
+        /// The envelope's decay time, in seconds.
         public func setDecayTime(_ decay: Float) {
             Synth.api.pointee.setDecayTime.unsafelyUnwrapped(pointer, decay)
         }
 
+        /// The envelope's sustain level, 0...1.
         public func setSustainLevel(_ sustain: Float) {
             Synth.api.pointee.setSustainLevel.unsafelyUnwrapped(pointer, sustain)
         }
 
+        /// The envelope's release time, in seconds.
         public func setReleaseTime(_ release: Float) {
             Synth.api.pointee.setReleaseTime.unsafelyUnwrapped(pointer, release)
         }
@@ -142,6 +146,7 @@ extension Sound {
             Synth.api.pointee.setTranspose.unsafelyUnwrapped(pointer, halfSteps)
         }
 
+        /// Modulates the synth's frequency.
         public var frequencyModulator: SignalValue? {
             get { SignalValue.wrap(Synth.api.pointee.getFrequencyModulator.unsafelyUnwrapped(pointer)) }
             set {
@@ -150,6 +155,7 @@ extension Sound {
             }
         }
 
+        /// Modulates the synth's amplitude.
         public var amplitudeModulator: SignalValue? {
             get { SignalValue.wrap(Synth.api.pointee.getAmplitudeModulator.unsafelyUnwrapped(pointer)) }
             set {
@@ -170,12 +176,14 @@ extension Sound {
             Synth.api.pointee.setParameter.unsafelyUnwrapped(pointer, Int32(parameter), value) != 0
         }
 
+        /// Modulates a generator parameter.
         public func setParameterModulator(_ parameter: Int, _ modulator: SignalValue?) {
             retain(modulator)
             Synth.api.pointee.setParameterModulator.unsafelyUnwrapped(pointer, Int32(parameter),
                                                               modulator?.pointer)
         }
 
+        /// The modulator installed on a generator parameter, if any.
         public func parameterModulator(_ parameter: Int) -> SignalValue? {
             SignalValue.wrap(Synth.api.pointee.getParameterModulator.unsafelyUnwrapped(pointer, Int32(parameter)))
         }
diff --git a/Sources/PlaydateKit/Sound/Synth/Enumerations/Synth.Waveform.swift b/Sources/PlaydateKit/Sound/Synth/Enumerations/Synth.Waveform.swift
index e78929f..7de492a 100644
--- a/Sources/PlaydateKit/Sound/Synth/Enumerations/Synth.Waveform.swift
+++ b/Sources/PlaydateKit/Sound/Synth/Enumerations/Synth.Waveform.swift
@@ -8,8 +8,11 @@ extension Sound.Synth {
         case sine = 2
         case noise = 3
         case sawtooth = 4
+        /// A Pocket Operator-style phase-distortion waveform.
         case poPhase = 5
+        /// A Pocket Operator-style digital waveform.
         case poDigital = 6
+        /// A Pocket Operator-style VOSIM (voice simulation) waveform.
         case poVosim = 7
 
         var cValue: SoundWaveform { SoundWaveform(SoundWaveform.RawValue(rawValue)) }
diff --git a/Sources/PlaydateKit/Sprite/Classes/Sprite.swift b/Sources/PlaydateKit/Sprite/Classes/Sprite.swift
index aad29cd..2089237 100644
--- a/Sources/PlaydateKit/Sprite/Classes/Sprite.swift
+++ b/Sources/PlaydateKit/Sprite/Classes/Sprite.swift
@@ -1,10 +1,16 @@
 internal import CPlaydate
 
+/// The cached `playdate->sprite` C API table.
 private var spriteAPI: UnsafePointer<playdate_sprite> { Playdate.spriteAPI.unsafelyUnwrapped }
 
 /// A sprite: a drawable object with position, z-order, and collision
 /// support. Wraps `LCDSprite`. Static members wrap the global sprite
 /// system functions.
+///
+/// The binding stores a back-reference to each `Sprite` wrapper in the
+/// underlying `LCDSprite`'s userdata slot, so callbacks and queries can
+/// recover the wrapper. Do not mix these wrappers with C code that sets
+/// its own sprite userdata; use `userdata` for per-sprite storage instead.
 public final class Sprite {
     let pointer: OpaquePointer
     let isOwned: Bool
@@ -269,11 +275,13 @@ public final class Sprite {
         set { spriteAPI.pointee.setUpdatesEnabled.unsafelyUnwrapped(pointer, newValue ? 1 : 0) }
     }
 
+    /// Whether the sprite participates in collisions.
     public var collisionsEnabled: Bool {
         get { spriteAPI.pointee.collisionsEnabled.unsafelyUnwrapped(pointer) != 0 }
         set { spriteAPI.pointee.setCollisionsEnabled.unsafelyUnwrapped(pointer, newValue ? 1 : 0) }
     }
 
+    /// Whether the sprite is drawn.
     public var isVisible: Bool {
         get { spriteAPI.pointee.isVisible.unsafelyUnwrapped(pointer) != 0 }
         set { spriteAPI.pointee.setVisible.unsafelyUnwrapped(pointer, newValue ? 1 : 0) }
diff --git a/Sources/PlaydateKit/Sprite/Enumerations/CollisionResponse.swift b/Sources/PlaydateKit/Sprite/Enumerations/CollisionResponse.swift
index a0ec242..bb2d95d 100644
--- a/Sources/PlaydateKit/Sprite/Enumerations/CollisionResponse.swift
+++ b/Sources/PlaydateKit/Sprite/Enumerations/CollisionResponse.swift
@@ -3,9 +3,13 @@ internal import CPlaydate
 extension Sprite {
     /// How a sprite reacts when a collision occurs.
     public enum CollisionResponse: UInt32, Sendable {
+        /// The sprite slides along the edge of the other sprite.
         case slide = 0
+        /// The sprite stops at the point of collision.
         case freeze = 1
+        /// The sprite passes through, still reporting the collision.
         case overlap = 2
+        /// The sprite bounces off the other sprite.
         case bounce = 3
 
         init(_ response: SpriteCollisionResponseType) {
diff --git a/Sources/PlaydateKit/Sprite/Structures/Rect.swift b/Sources/PlaydateKit/Sprite/Structures/Rect.swift
index d01f8b0..deaa8b0 100644
--- a/Sources/PlaydateKit/Sprite/Structures/Rect.swift
+++ b/Sources/PlaydateKit/Sprite/Structures/Rect.swift
@@ -7,6 +7,7 @@ public struct Rect: Sendable {
     public var width: Float
     public var height: Float
 
+    /// Creates a rect from an origin and size.
     public init(x: Float, y: Float, width: Float, height: Float) {
         self.x = x
         self.y = y
diff --git a/Sources/PlaydateKit/Support.swift b/Sources/PlaydateKit/Support.swift
index 3e074a5..7098972 100644
--- a/Sources/PlaydateKit/Support.swift
+++ b/Sources/PlaydateKit/Support.swift
@@ -1,5 +1,10 @@
 internal import CPlaydate
 
+/// Internal C-string helpers shared by the wrappers.
+///
+/// The conversions are implemented manually (rather than with
+/// `String(cString:)` / `withCString`) so the module stays within the
+/// Embedded Swift subset used for device builds.
 extension String {
     /// Creates a string by copying a null-terminated UTF-8 C string.
     init(playdateCString pointer: UnsafePointer<CChar>) {
diff --git a/Sources/PlaydateKit/System/Classes/MenuItem.swift b/Sources/PlaydateKit/System/Classes/MenuItem.swift
index 98a3113..48dcbe0 100644
--- a/Sources/PlaydateKit/System/Classes/MenuItem.swift
+++ b/Sources/PlaydateKit/System/Classes/MenuItem.swift
@@ -8,6 +8,8 @@ extension System {
         /// Retains C strings passed to the OS for option titles.
         private var retainedOptionTitles: [UnsafeMutablePointer<CChar>] = []
 
+        /// Wraps the C menu item; fails (and frees the retained titles) if
+        /// `pointer` is nil.
         init?(pointer: OpaquePointer?,
               retainedOptionTitles: [UnsafeMutablePointer<CChar>] = [],
               onSelect: @escaping (MenuItem) -> Void) {
diff --git a/Sources/PlaydateKit/System/Structures/Info.swift b/Sources/PlaydateKit/System/Structures/Info.swift
index ce0aa1b..a5ea6fc 100644
--- a/Sources/PlaydateKit/System/Structures/Info.swift
+++ b/Sources/PlaydateKit/System/Structures/Info.swift
@@ -1,8 +1,11 @@
 extension System {
     /// OS, language, and pdx version information, mirroring `PDInfo`.
     public struct Info: Sendable {
+        /// The Playdate OS version.
         public let osVersion: UInt32
+        /// The system language.
         public let language: Language
+        /// The version of the game's pdx.
         public let pdxVersion: UInt32
     }
 }
diff --git a/Sources/PlaydateKit/System/Structures/PowerStatus.swift b/Sources/PlaydateKit/System/Structures/PowerStatus.swift
index 1ddb178..5abf7e9 100644
--- a/Sources/PlaydateKit/System/Structures/PowerStatus.swift
+++ b/Sources/PlaydateKit/System/Structures/PowerStatus.swift
@@ -6,8 +6,11 @@ extension System {
         public let rawValue: UInt32
         public init(rawValue: UInt32) { self.rawValue = rawValue }
 
+        /// The battery is charging.
         public static let charging = PowerStatus(rawValue: UInt32(kPDPowerStatusCharging.rawValue))
+        /// Power is supplied over USB.
         public static let usb = PowerStatus(rawValue: UInt32(kPDPowerStatusUsb.rawValue))
+        /// Power is supplied through the accessory screw terminals.
         public static let screws = PowerStatus(rawValue: UInt32(kPDPowerStatusScrews.rawValue))
     }
 }
diff --git a/Sources/PlaydateKit/System/System.swift b/Sources/PlaydateKit/System/System.swift
index a3d9989..3b687ce 100644
--- a/Sources/PlaydateKit/System/System.swift
+++ b/Sources/PlaydateKit/System/System.swift
@@ -4,6 +4,7 @@ internal import CPlaydate
 public enum System {}
 
 extension System {
+    /// The cached `playdate->system` C API table.
     private static var api: UnsafePointer<playdate_sys> { Playdate.systemAPI.unsafelyUnwrapped }
 
     // MARK: - Memory
@@ -34,6 +35,7 @@ extension System {
 
     // MARK: - Time
 
+    /// The system language setting.
     public static var language: Language { Language(api.pointee.getLanguage.unsafelyUnwrapped()) }
 
     /// Milliseconds since the game launched. Wraps around after about 49 days.
@@ -53,21 +55,25 @@ extension System {
     /// High-resolution timer value, in seconds.
     public static var elapsedTime: Float { api.pointee.getElapsedTime.unsafelyUnwrapped() }
 
+    /// Resets the high-resolution timer to zero.
     public static func resetElapsedTime() { api.pointee.resetElapsedTime.unsafelyUnwrapped() }
 
     /// Offset from UTC of the user-set timezone, in seconds.
     public static var timezoneOffset: Int32 { api.pointee.getTimezoneOffset.unsafelyUnwrapped() }
 
+    /// Whether the user prefers 24-hour time display.
     public static var shouldDisplay24HourTime: Bool {
         api.pointee.shouldDisplay24HourTime.unsafelyUnwrapped() != 0
     }
 
+    /// Converts seconds since the 2000-01-01 epoch to a calendar date.
     public static func convertEpochToDateTime(_ epoch: UInt32) -> DateTime {
         var dateTime = PDDateTime()
         api.pointee.convertEpochToDateTime.unsafelyUnwrapped(epoch, &dateTime)
         return DateTime(dateTime)
     }
 
+    /// Converts a calendar date to seconds since the 2000-01-01 epoch.
     public static func convertDateTimeToEpoch(_ dateTime: DateTime) -> UInt32 {
         var cValue = dateTime.cValue
         return api.pointee.convertDateTimeToEpoch.unsafelyUnwrapped(&cValue)
@@ -135,6 +141,8 @@ extension System {
 
     nonisolated(unsafe) private static var buttonCallback: ((Buttons, Bool, UInt32) -> Int32)?
 
+    /// Enables the given peripherals (e.g. the accelerometer), disabling
+    /// the rest.
     public static func setPeripheralsEnabled(_ peripherals: Peripherals) {
         api.pointee.setPeripheralsEnabled.unsafelyUnwrapped(PDPeripherals(PDPeripherals.RawValue(peripherals.rawValue)))
     }
@@ -153,6 +161,7 @@ extension System {
     /// The crank position in degrees; 0 points along the +Y axis.
     public static var crankAngle: Float { api.pointee.getCrankAngle.unsafelyUnwrapped() }
 
+    /// Whether the crank is folded into the device.
     public static var isCrankDocked: Bool { api.pointee.isCrankDocked.unsafelyUnwrapped() != 0 }
 
     /// Disables or enables the crank dock/undock sounds. Returns the previous setting.
@@ -164,6 +173,7 @@ extension System {
     /// Whether the user has the "flipped" system setting enabled.
     public static var isFlipped: Bool { api.pointee.getFlipped.unsafelyUnwrapped() != 0 }
 
+    /// Disables or re-enables the automatic screen lock.
     public static func setAutoLockDisabled(_ disabled: Bool) {
         api.pointee.setAutoLockDisabled.unsafelyUnwrapped(disabled ? 1 : 0)
     }
@@ -272,6 +282,7 @@ extension System {
     /// Battery charge, 0...100.
     public static var batteryPercentage: Float { api.pointee.getBatteryPercentage.unsafelyUnwrapped() }
 
+    /// The battery voltage, in volts.
     public static var batteryVoltage: Float { api.pointee.getBatteryVoltage.unsafelyUnwrapped() }
 
     /// Flushes the CPU instruction cache after loading code at runtime.
@@ -323,6 +334,7 @@ extension System {
     /// The system volume, 0...1.
     public static var volume: Float { api.pointee.getVolume.unsafelyUnwrapped() }
 
+    /// The battery and power supply state.
     public static var powerStatus: PowerStatus {
         PowerStatus(rawValue: UInt32(api.pointee.getPowerStatus.unsafelyUnwrapped().rawValue))
     }