Parity Flip

Tap or click a cell to flip it and its orthogonal neighbours. Continue until the grid matches the target. The optimal-move counter shows the minimum-flip solution length.

Parity Flip is a logic puzzle where flipping one cell on a grid also flips its neighbours. The goal is to convert a starting pattern to a target pattern using the minimum number of flips. The format is the Lights Out puzzle from 1995 with cosmetic restyling.

What works is the mathematical underpinning. Lights Out puzzles can be solved using linear algebra over GF(2), and skilled players develop intuition for the underlying matrix structure even without naming it. The format teaches mathematical thinking through play, which I respect.

Eighty puzzles across three grid sizes from 3x3 up to 5x5. Smaller grids solve through trial and inference. Larger grids start requiring systematic approaches that mirror Gaussian elimination, though the game does not require you to formalise this.

Tested over three commute sessions on the Mumbai locals. Touch with tap-to-flip works fine. Mouse-click works the same. The format does not depend on input speed; it depends on planning.

Where the game starts to thin is the absence of variation beyond grid size. Every puzzle uses the same flip rule and the same square-grid format. The original Lights Out had diagonal-flip variants and hex grids, plus time-based constraint modes, and none of those variants appear here. A more ambitious developer could have expanded the format.

Where I would push back is the absence of a 'show solution' button after multiple failed attempts. Lights Out is solvable from any starting state via the linear-algebra approach, and a player who gets stuck would benefit from seeing a worked solution. The current design has no escape hatch for stuck players.

Three stars. Functional Lights Out implementation with mathematical depth. Does not extend the format and the missing solution-reveal hurts retention.