StackWorks — Classic Chess Help & Rules

Classic Chess uses standard chess movement and check rules: check, checkmate, stalemate, castling, en passant, and promotion.

Rules Overview
Movement & Check
Special Moves
Repetition & Draws
Using the Interface
PGN Import & Export
FEN Copy/Share
Notation

Rules Overview

Movement (Chess)

Pieces move like chess: King, Queen, Rook, Bishop, Knight, Pawn.
Check rules apply: you may not make a move that leaves your king in check.
Castling and en passant exist when allowed by the current state.
Promotion happens on reaching the final rank.

Repetition & Draws (Chess-style)

Threefold repetition (claimable draw): if the same position occurs at least 3 times, the player to move may claim a draw.
Fivefold repetition (automatic draw): if the same position occurs at least 5 times, the game is drawn automatically.

Movement & Check

Select a piece to see legal destinations. Legal moves are highlighted.

        Check reminder: A move is illegal if it leaves your king in
        check.
      

Special Moves

Castling

Castling is a king move of two squares on the home rank; the rook moves to the square next to the king.
You cannot castle out of, through, or into check.

En Passant

When a pawn advances two squares, it may be captured en passant on the immediately following move.

Promotion

When a pawn reaches the final rank, it is promoted.

Repetition & Draws

Repetition is based on repeating the same position, not repeating the same moves.

        The same position means: same player to move, same piece placement, and
        the same relevant rights (castling rights and en passant state).
      

Using the Interface

Undo/Redo are available in Option Actions.
Flip board rotates the board 180°.
Coordinates toggles file/rank labels.
Layout (Options → Layout) switches between Panels (sidebars) and Menu (tap ☰ to open panel sections as dialogs).
Evaluation (right panel → Evaluation) can show Engine Eval (Stockfish), Material, Mobility, Center, or Threats.
In Engine Eval mode, enable Show on board to display the vertical eval bar beside the board.
Engine Eval also shows a move-by-move evaluation graph for the current line. The graph follows the whole game, including terminal mate/draw positions, and you can click it to jump to a position in Move History.
Inside squares draws coordinates on the board itself: lowercase file letters in the bottom row (lower-right of each square) and rank numbers in the left column (upper-left of each square). The label color uses the opposite square’s base color for contrast.
Board theme changes the checkerboard background (Classic/Green/Blue/Stone/Burled Wood/Candy).
Theme changes the piece style (2D/3D/Neo/Candy).
Save/Load lets you export or restore a game state. After loading a Chess save, playback returns to Start so you can run forward from the beginning of the saved line.

Keyboard shortcuts

Shortcuts use Ctrl (Windows/Linux) or Cmd (macOS). Shortcuts are disabled while typing in a text field.

Undo: Ctrl/Cmd+Z
Redo: Ctrl/Cmd+Y or Ctrl/Cmd+Shift+Z
Save: Ctrl/Cmd+S
Toggle analysis: Ctrl/Cmd+Shift+A
Resign: Ctrl/Cmd+Shift+X
Full Screen: Ctrl/Cmd+Shift+F (or the Full Screen button)
Toggle layout: Ctrl/Cmd+Shift+L
Toggle toast messages: Ctrl/Cmd+Alt+T
Playback play/pause: Space (during playback)
Bot pause/resume: Space (during live play when a bot is enabled and playback is not active)
Bot speed: Alt+↑/Alt+↓ (when the bot speed control is available)
Playback speed: Alt+Shift+↑/Alt+Shift+↓
Show keyboard shortcuts: Ctrl/Cmd+Shift+? (also works as Ctrl/Cmd+Shift+/)
Right-click menu: Right-click outside the board → Show Keyboard Shortcuts

Analysis mode (private sandbox)

Toggle via the Analysis button or Ctrl/Cmd+Shift+A.
In online rooms, moves made in Analysis mode are local-only and are not submitted to the server.
Your opponent does not see your Analysis mode or analysis moves.
AI/bots are paused while analysis is enabled, and restored when you exit.
Move any piece freely: Both sides' pieces are selectable—click a piece of either color to move it using legal moves. The evaluation panel stays live so you can assess each hypothetical position.
Leaving Analysis returns you to the live game state.

Board visualization (arrows & highlights)

Draw arrows (desktop): Right-click and drag from one square to another.
Knight arrows: If the drag is a knight move (2×1), the arrow draws as a 90° “L” shape.
Highlight squares (desktop): Right-click a square (default, or press S).
Circle highlight: Press C while / after right-clicking.
Push pin: Press N while / after right-clicking.
Protect: Press P while / after right-clicking.
Number labels: Press 0-9, then right-click a square.
Remove: Press X on desktop to arm selective erase, then right-click a square — removes number first, then pin/protect, then square/circle.
Colors (desktop): Orange (default), Shift = Green, Ctrl = Red, Alt = Blue.
Clear all annotations: Alt+X (works even on layouts where Alt changes the typed character).

Move Preview

In-game move previews are controlled via left panel → Options → Move preview. This single selector replaces the older split between preview hints and square-highlighting.

Use it to switch between Off, Classic, Classic squares, and Modern, which emphasizes the selected square and shows empty destinations as dots and occupied capture targets as rings.

When Move preview is set to Off, the separate Selection option lets you keep a Classic ring, Classic square, or Modern selected-square highlight.

        Touch / tablet (Analysis mode): On touch devices, a small swatch
        palette appears below the board while Analysis is enabled.
      

Pick color: Tap a color swatch (Orange/Green/Red/Blue) to set the annotation color.
Draw arrows: Touch and drag from one square to another.
Play moves: Tap the Play type button, then tap squares to move pieces. (Turning on Play disables Erase.)
Place annotation: Tap a type button (Square / Circle / Pin / Protect / 0-9) then tap a square.
Remove annotation: Tap the Erase button then tap a square; or tap the Remove type button (X) then tap a square — removes number first, then pin/protect, then square/circle.
Clear all: Tap the Clear swatch (black square with a red X).

PGN Import & Export

You can import/export games using PGN (Portable Game Notation). This is useful for sharing games with other chess tools or importing a game from elsewhere.

Import (Paste or Upload)

Open Option Actions and choose Import PGN (paste) or upload a .pgn/.txt file.
Import rebuilds the game from the standard starting position and populates the Move History.

Note: PGN import is offline-only for now. In online rooms, the server is authoritative and imported moves are blocked.

Warning: If a game is already in progress, clicking either Import PGN button will show a confirmation prompt before proceeding. The current game will be lost once you confirm.

Export (Current Line)

Export PGN exports the game up to the currently selected position in Move History.
If you've jumped back in history, exporting will export that line (not necessarily the full game).
Games ended by resignation are exported correctly — the resignation is recorded in the PGN result header and does not appear as a phantom move.
Filenames: Chess PGN exports and Chess JSON saves use the same filename format; only the extension differs (.pgn vs .json).
If a bot is playing a color, that color name is used in the filename for that side (white or black). If a human player has no name set, human is used.
The Include move times checkbox applies to both Save Game and Export PGN. When enabled, JSON saves keep recorded move times and PGN exports include [%emt] comments; when disabled, both exports omit move timing.
The Include engine evals checkbox applies to Export PGN. When enabled, exported PGNs include cached engine comments as [%eval]. When importing a PGN that already contains [%eval] comments, the evaluation panel and graph replay those embedded values first and only fall back to Stockfish for positions that do not have them.

FEN Copy/Share

FEN (Forsyth–Edwards Notation) is a compact string that describes a single chess position.

        Copy FEN from any move: Right-click any Move History entry and
        choose Copy FEN. This copies the FEN for that exact position to
        your clipboard.
      

You can paste the FEN into chess analysis tools, share it with a friend, or use it to report/debug a position.

Players (Optional)

Classic Chess supports optional bot opponents. Open Game Panel → Players. For each side, first choose Human or Bot. If you choose Bot, a second dropdown lets you pick a tier (Beginner / Intermediate / Advanced / Master).

Speed uses a slider (milliseconds). The current value is shown as an ms readout.
Use the ↺ button to reset speed to the default.

        Warmup note: The first time Stockfish loads, it may take a while
        (WASM compile/download). The UI will show a warmup message while it
        initializes.
      

        Pause/resume: When the bot is paused on its turn, an on-screen
        toast appears (for example:
        “White’s turn. Tap here ore press spacebar to resume bot”). Tap
        the toast itself to resume.
      

        Playback timing: If Use recorded move times is checked in
        Playback, the fixed playback speed slider is disabled and replay uses
        the saved per-move timing instead.
      

Local engine option: If in-browser Stockfish doesn’t work well on your device, you can run the local Stockfish HTTP server and configure the web app with VITE_STOCKFISH_SERVER_URL.

Notation

The move list uses a simple square-to-square notation, using → for moves and × for captures.

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