How Siege Chess works

You play a chess engine, one human against one machine. It's standard chess — no new pieces, no new moves.

• You defend as Black. The engine attacks as White, at full strength, every game. (The quiet link under Play swaps sides if you'd rather defend as White.)
• It bets it can checkmate you by move N. You pick N (15–60) with the slider — the ELO under the number says roughly how strong a player that goal is.
• Reach move N alive and you win. A draw counts as surviving — stalemate, repetition, insufficient material, the 50-move rule: all yours.
• Win and the next game suggests a longer N; lose and it suggests a shorter one. The deadline is the difficulty — the engine is never weakened.
• The timer changes the pressure, not the bet. Slide it anywhere from 1 to 10 minutes — or all the way right to No Timer for a game you can park and resume for up to 3 days.