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).
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).
Theme changes the piece style (2D/3D/Neo).
Save/Load lets you export or restore a game state.

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)
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.
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.
Colors (desktop): Orange (default), Shift = Green, Ctrl = Red, Alt = Blue.
Clear (desktop): Left-click anywhere on the board.

        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.
Highlight squares: Double-tap a square.
Clear all: Tap the Clear swatch (black square with a red X).
Erase mode: Tap the Erase swatch to toggle erase mode. While enabled, double-tap removes an existing square highlight and a touch-drag removes an existing arrow.

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.

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).

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.

Bot (Optional)

Classic Chess supports optional bot opponents. Open Game Panel → Bot and set White and/or Black to a tier (Beginner / Intermediate / Strong).

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 to resume bot”). Tap the toast itself to
        resume.
      

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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