ReverseChess

How it works

The Last Move

1. You are shown a chess position, never the game that led to it.
2. Drag a piece backwards to the square it came from.
3. If it captured something, say what, and put it back.
4. Only one answer keeps the whole story legal.

Unwind

1. Unwind gives you a goal, such as “Before the black pawn left a7”.
2. Take back several moves in a row, one at a time, and the last position you reach must meet the goal.
3. Wrong steps are allowed until you press Check, which flags the first one that could not have happened.
4. Only one chain of take-backs gets there.

Proof Game

1. You are shown a position reached by a real game from the starting position, and told how many half-moves it took.
2. Take every move back, one at a time, until the board is the starting position again.
3. Castling rights and the en passant square must come out right as well, not only the pieces.
4. Only one game gets there. Move order matters.

The Rota

1. You are shown where each worker ended up on the site, and where the rota meant them to be.
2. Pick two workers to unswap them, one step at a time, until everyone is back on the intended rota.
3. Every clue must hold for the whole sequence of swaps, and no longer sequence fits them.
4. Then name the opening gambit: which of the first two workers to swap started it.