dorado-hd/docs/apps/checkers.md

Checkers

• Official package: Checkers.exe (checkers)
• Corpus: Zune HD Apps (Decompiled)/checkers (external, untracked)
• Wave: W2 · Category: games
• Status: native · Complexity: TBD
• Dorado-HD id: checkers

Synthesized from the decompiled reference. No Microsoft code, strings, or assets are copied; behavior is re-derived and all content is re-authored.

1. Device behavior (mined)

Assembly	Types	Methods	Source lines
Checkers.exe	58	273	7603
Microsoft.Xna.Zune.dll	110	825	15694
ZuneCoreLib.dll	64	253	5197
ZuneGamesLib.dll	25	129	2513

• Native 272x480 portrait Zune HD app; board is a 34 px grid starting at y=92, with a board-flip flag for playing Black from the top.
• The engine is an 0x88 draughts search core (16x16 array with rank<<4|file indexing, SQUARE/RANK/FILE), not the visual 8x8 coordinates.

2. Screens & navigation

• Boot: LoadingScreen → MainMenuScreen with five entries — Single Player, Multiplayer, Learn To Play, Records, Options. (Checkers!MainMenuScreen..ctor)
• Single Player opens SinglePlayerSetUpScreen if no autosave exists, else a LoadSaveScreen asking to resume. Setup has Mode (Regular/Suicide), Difficulty (easy/intermediate/hard), Play As (side) and Color/theme toggles, then a Play button or Back. (Checkers!SinglePlayerSetUpScreen..ctor)
• Multiplayer chain: MultiplayerModeScreen → HostScreen / SearchScreen / LobbyScreen / WifiGameScreen over NetworkManager session state.
• In game: HUD shows player/opponent names, the current game-mode label, a difficulty strip drawn at (106,455), a status/thinking animation, and two buttons — but_undo (bottom right) and but_pause (bottom left). The last move and any multi-jump squares are highlighted. (Checkers!GameScreen..ctor)
• Pause: SinglePlayerPauseScreen (or MultiplayerPauseScreen) with resume / options / learn / main-menu entries; leaving mid-game saves a SaveSlot.
• End of game pushes EndOfGameScreen (win/lose/draw banners); a DrawOfferScreen exists for offered draws. Records are shown on RecordsScreen; rules and controls live in two scrollable tabs of LearnToPlayScreen.

3. Rules, scoring & progression

• 8x8 board, 12 men per side, play only on dark squares. Men move one square diagonally forward; kings move one square in any of the four diagonals. (Evaluate.normaldir, Evaluate.crowndir)
• Capture by jumping an adjacent enemy piece to the empty square beyond; men jump forward only, kings any diagonal direction. Captures are mandatory: move generation emits only jump moves when any exist (ForceJumpEnabled = true; generation sets OnlyJumpsAvailable). (Checkers!Evaluate.generate_move_list_for_player)
• Multi-jumps are recursive chains; a chain move is encoded with special = 2 (MOREJUMPS) plus a jumped_squares list, and a man that finishes on rank 0/7 is crowned (special = 1, promoted_piece = KING). (Checkers!Evaluate.create_multijump_move, Checkers!Evaluate.move_type)
• Evaluation is material + positional: man = 1000, king = 1399; center-square bonus table (0/1/2/4), per-rank advancement bonus up to 1500 for a man one rank from crowning, mobility, attack/defense bonuses; constants include MULTI_JUMP_BONUS = 1000 and CROWNING_BONUS = 200. (Checkers!Evaluate.piece_value)
• Search is negascout/minimax, iterative deepening, with killer moves, history and static-exchange pruning (MaxPly = 100, MaxGenMoves = 250). The game asks for a fixed depth per difficulty, with a companion time budget: easy = 1 ply, intermediate = 3 plies, hard = 8 plies. Hint is a 4-ply search. (Checkers!engine.Ziggurat_move, Checkers!engine.Ziggurat_depth_move, Checkers!engine.GetHint)
• No opening book: engine.make_opening_book_move always returns false.
• Suicide mode inverts the evaluator's sign so the search plays to lose (misère); regular mode is normal. Draws/stalemates end the game. (Checkers!engine.Ziggurat_move, Checkers!Evaluate)
• Progression is stat tracking, not unlockables: StatTracker keeps wins/losses/draws per difficulty (easy/intermediate/hard) and per WiFi, separately for Regular and Suicide modes; RecordsScreen displays them. (Checkers!StatTracker.IncreaseWin)
• SaveSlot persists FEN string, difficulty, colors, flipped board, suicide mode and both players' elapsed times; GetFenString/LoadFenString back the in-game save/restore. Undo takes back two half-moves; a warning popup appears once four undos have been used. (Checkers!GameScreen..ctor)

4. Controls

• Tap own piece → tap a highlighted destination to move. Tap selection is validated against engine move starts, not raw board geometry. (Checkers!BaseGameScreen.HandleTouchesBegan)
• Press-and-drag from an own piece switches to a "ghost" piece that follows the finger; release over a legal destination commits the move. (Checkers!BaseGameScreen.HandleTouchesMoved, ...HandleTouchesEnded)
• Buttons: undo and pause; board coordinates flip when playing Black so the human's pieces are always at the bottom.

5. Content inventory (must be re-authored)

• 92 files total: 71 PNG images, 16 XNB sounds, 5 XML text files (Text/Strings/en.xml, es.xml, fr.xml, Text/Fonts.xml, Text/Text.xml).
• Board art (wood theme, bg_game, bg_main, bg_loading), piece sprites (piece_* base/man/king), selection/glow/explosion/beam effects, win/lose banners, and two full rule/control illustration sets for Learn To Play (ltp_board, ltp_move, ltp_jump, ltp_forcejump, ltp_multijump, ltp_king, ltp_slide1/2, ltp_drag, ltp_pause, ltp_undo).
• Sound inventory includes ButtonDown, PieceMovement, PieceJump, PieceDestruction, KingMeGood/KingMeBad, DefeatFanfare, DrawFanfare and ScreenTransVert. All art/sound/text must be re-authored.

6. Implementation plan

• Pure-Kotlin engine as an object + immutable state/data class in ui/apps/games/; Compose screen through DetailScaffold; zero corner radius; colors/sizes from LocalDoradoColors/DoradoTokens; moves through SfxBank; stats/records through graph.games; persistence through graph.appState.
• Engine surface sketch:

  object CheckersEngine {
      fun legalMoves(state: CheckersState, color: CheckersColor): List<Move>
      fun apply(state: CheckersState, move: Move): CheckersState
      fun bestMove(state: CheckersState, level: Int): Move?
  }
  

• Unit tests in app/src/test/java/com/heretek/dorado_hd/LogicTest.kt.

Fidelity deltas vs existing CheckersEngine (MoreGames.kt)

1. No difficulty levels. Existing AI is a single greedy aiMove that picks the longest jump. Official needs easy/intermediate/hard = 1/3/8-ply negascout, plus a 4-ply hint, with positional evaluation (center, rank, mobility) rather than jump distance.
2. No Suicide mode. Setup Mode toggle and sign-inverted evaluation are missing; add it to the engine state and score/records.
3. No undo. Official takes back two half-moves (with a warning after four undos); the Kotlin engine has no move history.
4. No save/resume. Official persists a FEN + difficulty + clock via SaveSlot; grid state is only in Compose memory today.
5. No records. StatTracker wins/losses/draws per difficulty/mode and a Records screen are absent; only a single graph.games.record call exists.
6. AI is synchronous in UI. The official engine searches on a worker with an IsAIThinking flag; the Kotlin call must move to Dispatchers.Default and show a thinking state.
7. Rules are otherwise faithful — forced captures, recursive multi-jump, crowning and "no move = loss" are already correct; add explicit tests for forced-jump and king capture-direction parity.

7. Citation log

• Checkers!engine.game_difficulty · Checkers!engine.Ziggurat_move
• Checkers!engine.Ziggurat_depth_move · Checkers!engine.GetHint
• Checkers!Evaluate.generate_move_list · Checkers!Evaluate.generate_move_list_for_player
• Checkers!Evaluate.create_multijump_move · Checkers!Evaluate.move_type
• Checkers!Evaluate.piece_value · Checkers!BaseGameScreen.HandleTouchesBegan
• Checkers!BaseGameScreen.HandleTouchesMoved · Checkers!BaseGameScreen.HandleTouchesEnded
• Checkers!MainMenuScreen..ctor · Checkers!SinglePlayerSetUpScreen..ctor
• Checkers!GameScreen..ctor · Checkers!LearnToPlayScreen..ctor
• Checkers!StatTracker.IncreaseWin · Checkers!SaveSlot · Checkers!Evaluate.normaldir · Checkers!Evaluate.crowndir