Immortal Rex Chess: Chess variant with a T-Rex hunting each king

About Immortal Rex Chess

Chess with two T-Rexes nothing can stop: each stomps one step towards a king every four moves. Checkmate first, or keep running.

Immortal Rex Chess is chess with a T-Rex hunting each king. Every piece moves as in ordinary chess, and you play White against the computer. Two Rexes stand in the middle of the board, the black Rex on e5 and the white Rex on e4, and no one moves them. After every fourth move by the computer, which plays Black, both take one step towards the king they hunt.

A Rex cannot be captured, and no piece can move onto it or past it. It destroys any piece on the square it steps onto, of either colour. If it steps onto the king it hunts, that side loses; checkmate still wins as well. A king left at home is eaten after about sixteen moves, so every game is a race: mate the computer first, or make room around your king and dodge around the Rex. A win against Medium scores the number of moves it took, and the fewest go on the monthly leaderboard.

How to play

Pick a level — Medium is the ranked one — and press Start. You play White and move first.
Tap a piece to see where it can go, then tap a square to move it. Pieces move as in ordinary chess.
Watch the Rexes: the board marks the square each will step onto next, and counts the moves until they step.
After every fourth move by the computer, both Rexes step towards their kings, destroying whatever stands on that square.
Checkmate the computer, or let its Rex catch its king, before the black Rex catches yours.
A win against Medium scores the moves it took. Sign in to put it on the monthly board.

Tips

Count before you move: the marked squares show exactly where the Rexes go next, so you can always see the danger coming.
Give your king room early. A king boxed in by its own pawns cannot get out of the Rex’s way in time.
A Rex is a wall. Use it to block a check, or to shield a piece from a rook or a bishop.
Do not leave a piece on a Rex’s next square unless you mean to lose it — the Rex takes your pieces as well as the computer’s.
The computer’s king is hunted too. Keeping it boxed in can win the game without a checkmate.

Questions players ask

How is a win scored?

By the number of moves you made: fewer is better. Only wins against Medium go on the board; losses, draws and resignations are recorded but never score.

Can a Rex be stopped?

No. It cannot be captured or blocked. A Rex only waits when every square nearer its king is taken by the other Rex or the other king.

What if both kings are eaten at once?

Both Rexes step in the same round, so it can happen. The game is then a draw.

When does the leaderboard reset?

On the 1st of every month at 00:00 UTC. The final standings are kept: the top three of each month receive an honour on their profile, and your best never resets.

Do I need an account to play?

No. Press Start and you play straight away under a guest name. Sign in with an account you already have to put your wins on the monthly leaderboard.