How to play
You start with every cell lit. Clicking a cell toggles it along with the cells directly above, below, left, and right of it (diagonal cells aren't affected). Turn off every light to make the screen completely dark and clear the puzzle.
The logic behind this puzzle
This is a classic logic puzzle where each cell is treated as a two-state switch β on or off β and the effect of a click on nearby cells can be calculated mathematically usinglinear algebra over the field of 2 (mod-2 arithmetic). Clicking the same cell twice returns it to its original state, so in the end each cell only ever needs to be pressed or not pressed β finding the right combination is the key to solving the puzzle.
Frequently Asked Questions
Is every puzzle always solvable?
Yes β this game always starts from a state that's guaranteed to be solvable. The starting screen is generated by working backward from a solution and applying random clicks, so there's always a way to turn off every light.
Are there other logic puzzles?
Yes β check out the Nonogram Puzzle Game for another kind of logic puzzle.