Chomp Game Online Free
Take turns eating squares of a chocolate bar. Each bite eats the square you pick and every square below it and to its right. Whoever has to eat the poisoned square loses.
Tap a square to see what it would eat, then tap it again to eat it.
What is Chomp?
Chomp is a two-player game played with a rectangular chocolate bar whose top-left square is poisoned. On your turn you choose any square and eat it, along with every square below it and to its right. The player who is left with only the poisoned square has to eat it and loses.
The game was popularised by the mathematician David Gale in 1974. It has a surprising property: there is a short proof that the first player can always win on any rectangle, but the proof doesn’t say which move to make. The computer on Hard works it out by checking every position.
How to play Chomp Game
- The bar starts whole. The top-left square, marked ☠, is poisoned. Blue moves first.
- On your turn, pick any square except the poisoned one. That square and every square below it and to its right are eaten.
- Tap a square to see which squares would go, then tap it again to eat them.
- When only the poisoned square is left, the player to move must eat it and loses. Play against the computer at Easy, Medium or Hard, or choose 2 Players to take turns on one device. Undo takes back your last move, and an unfinished game is saved if you leave the page.
Chomp Game skills
- Thinking ahead
- Spotting winning positions
- Logical reasoning
Level: Ages 7 and up
Tips for Chomp
If you can leave just the poisoned square’s row and column with the same number of squares in each, an L shape, copy your opponent’s bites on the other arm and you’ll win.
On a square bar, the first move is easy: eat the square diagonally next to the poison. That leaves an even L shape.
With two rows left, leave the top row one square longer than the bottom row. Every move your opponent makes, you can restore that shape.
Chomp Game questions and answers
How do you play Chomp?
Pick any square of the chocolate bar and eat it along with every square below and to the right of it. Players take turns, and whoever is forced to eat the poisoned top-left square loses.
Who wins Chomp?
The first player can always win on any rectangular bar. The proof is a “strategy-stealing” argument: if eating just the bottom-right square were a losing move, the first player could have played the winning reply instead. It proves a winning move exists without saying what it is.
Is there a strategy for Chomp?
For square bars and bars with two rows there are simple winning strategies (see the tips). For bigger rectangles no simple rule is known, so the winning moves have to be worked out by checking positions, which is what the computer does.
Is Chomp a math game?
Yes. It comes from combinatorial game theory, and it’s a classic example of a game where mathematicians know who wins but not how. It can also be described as a game of picking divisors of a number.