An equation built from matchsticks — and it is false. Fix it with the smallest change allowed: move a stick, remove one, or add one. On hard, you get two.
You get a simple equation — an addition or a subtraction — drawn in matchsticks, and the result is wrong as it stands. Make it true using only the change the puzzle allows:
Digits change as their sticks change: one stick turns 6 into 5, 7 into 1, 9 into 8. The operator can change too — a single stick turns + into −, which is the move most people see last.
Each level unlocks after five wins on the one before it.
There is no puzzle library behind this game. Every puzzle is generated the moment you ask for it: the site starts from a true equation and breaks it using the reverse of the change you will be asked to make — so for a remove puzzle, the generator adds a stick, and taking it away is the answer.
Then comes the guard: a solver that tries every possible change before the board reaches your screen. No puzzle without a solution is ever shown, the number of solutions is known, and the easy level accepts only puzzles whose solution is unique.
Digits are drawn on a straight seven-segment grid, and the symbols for multiplication and division are diagonal. Adding a diagonal would mean distorting every other shape to accommodate it — so the puzzles stay on two operators, plus an equals sign that can itself be rebuilt on the hard level.
Psychologists call these insight puzzles: the answer does not arrive by step-by-step calculation but by breaking an assumption you did not notice you were making. Nearly everyone starts by hunting for a change in the digits, and only later realises the operator itself is made of sticks too.
What practice reliably improves is your performance on these puzzles — you start checking the operator sooner. Whether it carries over to solving problems outside the game is far less certain, and the evidence for that kind of transfer is weak.
Completely free with no subscription, and it runs in the browser with nothing to install. You start instantly as a guest; signing in is optional and only saves your points across devices.
Press Undo to take the step back, or Reset to start the puzzle again. Nothing is lost by trying.
Not at first. The first hint tells you where to look, the second lights the stick, and only the third reveals the solution — which passes the puzzle with no points.
NumGrid: four numbers and one target across 500 levels. Sudoku with four tiers that scale forever. And if you want numbers on your own speed, memory and focus, take the brain test.