FIDE: 5-fold & 75-move are automatic draws; a resign with no mating material is a draw. USCF: no automatic 5-fold/75-move draw (the 3-fold/50-move claim still works) and a resignation always loses. Move rules, interface, clocks are identical.

1 = no limit. ≥2 would cap each side to one draw offer per N of their own full moves (a 50-move/3-fold claim is always allowed). Reserved: offer throttling is being reworked and is currently inactive — every offer goes through regardless of this value.

L5: every rule (current behaviour). L4: drops resign, the draw offer/agreement, and the flag-fall can't-mate draw (a fallen flag always loses); the 5-fold/75-move automatic draws move down to automatic 3-fold/50-move. Result codes: checkmate, stalemate, insufficient material, 3-fold, 50-move, win-on-time. L3: everything L4 drops, and also no insufficient-material draw and no repetition draw — only the 50-move rule survives. With no repetition key, the en-passant target is set on any two-square push (the capture is still filtered for legality, so play stays correct). Result codes: checkmate, stalemate, 50-move, win-on-time. L2: everything L3 drops, and also no clock at all (no time control, tick, flag-fall or clock display — the whole Time-mode axis is inert) and no 50-move rule. Only checkmate and stalemate remain. L1: everything L2 drops, and also no castling, no en-passant, and no two-square pawn push — pawns move exactly one square (promotion still works). Castling was the only thing that differed between Standard and Chess960 in the move engine, so at L1 the Standard/Freestyle choice no longer changes the engine — only the starting arrangement differs. L0: everything L1 drops, and also no check detection at all — every piece, the king included, is a pure geometric mover. Self-check is legal, there is no checkmate or stalemate, and the game ends when a king is captured (removed from the board). Promotion is always to a queen (no choice). Result codes: WK / BK (whoever took the enemy king) and D! — once only the two kings remain, the side to move gets one more half-move; if it doesn't capture the enemy king, it's a draw.

R plays a uniformly random legal move for Black — it reuses the engine's own move generator, so pins, check evasion, castling, en passant and promotion are all correct; it simply has no idea which move is good. Works in every interface and at every level. Cost: +79 B (clickable) / +92 B (text & prompt). Board rotation and the draw-offer limit are disabled while a bot is on: you always play White, and the bot never offers or accepts a draw. B1–B5 (search bots) are not yet enabled. Search depth (plies): 1 2 3 4

Multi-period (input · DOM · prompt). Each side gets the added time when it completes the threshold move. Per-period inc (blank = same as period 1) lets the increment activate later, e.g. 0→30s; input/DOM only. All increments 0 ⇒ sudden template (minimum bytes).

Empty = initial position. Works together with 960 too; castling rights are checked against the arrangement rooks. The castling field accepts classic (KQkq) or Shredder-FEN (rook file letters: A-H white, a-h black).