Puzzle

ASCII Lights Out

Switch off every light on a grid, where pressing one cell also flips the four cells around it.

Loading Lights Out...

Every game plays locally in your browser. Nothing about your play is uploaded to a server. Your high scores are kept in this browser on this device only, and you can clear anything these games have saved from the privacy page.

Controls

Arrow keys or WASDMove the cursor between cells.
Space or EnterPress the cell under the cursor, flipping it and its neighbours.
Arrow pad and buttonMove the cursor and press, on a touch screen.
RDeal a fresh board.

How to play

  1. Each board is a grid of lit and unlit cells. Move the cursor to a cell and press it to toggle that cell and its four orthogonal neighbours.
  2. Pressing a cell twice returns the board to where it was, and the order of presses does not matter, so the puzzle is a set of cells to press once each.
  3. Work the board row by row rather than chasing single lights, clearing one row at a time by pressing the row beneath it.
  4. Switch off every light to win. Your score is the number of presses it took, so a tidy solution beats a lucky one.

About Lights Out

Lights Out is a puzzle that looks like a toy and hides a piece of mathematics. Pressing a cell flips it and its four orthogonal neighbours, so every press undoes part of what the last one did, and poking at it by instinct tends to make a tidy board messy again. The trick the game is quietly teaching is that order does not matter and pressing a cell twice is the same as never pressing it - which means a solved board is just the right set of cells pressed once each.

Each new board is built by starting from all-dark and pressing a handful of random cells, so it is always solvable, and your job is to find the pressing that reverses it. A tidy solution is often shorter than it looks once you stop chasing single lights and work row by row. Your best is the fewest presses you have ever cleared a board in, saved on this device.

Frequently asked questions

Yes. Each board is built by starting from an all-dark grid and pressing a handful of cells at random, so the sequence that undoes those presses always exists. You may not find the shortest one, but there is never a board that cannot be cleared.

That is the rule the whole puzzle is built on. A press toggles the cell you aim at and its four orthogonal neighbours, the ones directly above, below, left and right. Cells on an edge have fewer neighbours, so they flip fewer lights, which is part of what makes the corners useful to think about.

Work from the top down. Clear the top row by pressing the cells in the row directly beneath each light that is still on, then repeat down the board. It feels wrong because you are lighting new cells as you go, but the pattern left on the bottom row tells you the small correction needed to finish.

While you are here

BNS Data Tools

The same team builds a set of free, privacy-first data and developer utilities - formatters, converters, validators and calculators - that run in your browser the same way these games do.

Open BNS Data Tools