Lights Out

Overview

Press one cell and four neighbors flip with it, which is why Lights Out behaves less like a grid puzzle and more like a quiet exercise in modular arithmetic. The board is a 5×5 array of lights, each on or off, and the only move is to tap a cell — which toggles that cell plus its orthogonal neighbors. The goal is to drive every light to off. Because every press flips a fixed cross of cells regardless of order, the question is not what sequence to press in but which subset of cells to press at all; solve it once and the order is irrelevant. This build ships twenty hand-set puzzles graded easy through hard, full-history undo so you can walk a move back without restarting, and a randomize button that generates a fresh scrambled board for as much play as you want. On a win, the game shows its optimal solution alongside yours, which is a quick way to learn how inefficient your path actually was.

How to Play

Click a cell (or tap it on touch) to toggle it and its up-to-four orthogonal neighbors. There are no other controls in the main game: every interaction is a single press on a single cell. Use undo freely — it rewinds your full move history one press at a time, which is the safest way to experiment without losing your line. Pick from the twenty preset puzzles to learn the feel, or hit randomize for a fresh scrambled board. When you clear a board, the optimal-solution comparison appears so you can measure your press count against the shortest possible.

Tips & Strategy

The classic approach is light-chasing: work from the second row down, pressing each cell in row N exactly when the cell directly above it in row N−1 is still lit, which clears the previous row as you go. Once you reach the bottom, only the final row's pattern tells you whether the puzzle is solvable from that opening — and which cells in the top row you should have pressed to fix it. Because toggling is its own inverse, pressing a cell twice is the same as not pressing it, so never press the same cell twice in a solution. Undo is your diagnostic tool: if you have made a mess, rewind to a known state rather than pressing forward. On the presets, the easy puzzles are small enough that intuition works, but the hard ones reward the chasing method plus a memorized table of bottom-row patterns. Compare your press count to the optimal on each win — a gap of more than a few presses usually means you are toggling cells that cancel each other out.