How it works
Every tap is its own undo: pressing the same light twice changes nothing. So a solution is simply a set of lights to press once, and the order does not matter. Each grid on the site is built so that exactly one such set exists.
Easy grids are 6×6 and need four to six presses. Medium grids are also 6×6 with eight to twelve, hard grids are 7×7 with fourteen to twenty. The counter shows your presses, and the hint lights up a press that belongs to the solution.
The chasing method
There is a reliable way through any grid. Work from the top row down: for every light that is on in a row, press the light directly below it. This switches off the row above without touching the rows you have already cleared.
When you reach the bottom, some lights in the last row will usually still be on. That pattern tells you which lights of the top row should have been pressed at the start. Press those in the top row, chase down again, and the grid goes dark.
Chasing finds a way out, not always the shortest. To trim it, remember that any light pressed twice cancels, and look for presses that match the starting picture.
Why each press counts once
A press always flips the same five lights, so two presses on one light cancel out and the order of presses never matters. Lights is therefore a puzzle about choosing which lights to press, not about finding a sequence. The counter on screen counts every tap, mistakes included, so a clean solve shows exactly the number of presses the solution needs.
Undo takes back one press at a time, and the board is stored in this browser for later.
Questions
Do diagonal neighbours flip?
No. Only the light you tap and the four lights that share an edge with it change.
Why are there no 5×5 grids?
On a 5×5 board some starting pictures have several different solutions. The site uses sizes where every picture has exactly one set of presses.
How fast should I be for the lamp?
Lights is the quickest Puzzle lamp: under one minute on easy days, two and a half on medium, four on hard, without a hint, gives three rays.
Are there numbered Lights puzzles?
Yes, 42 of them, each with its count of lit cells and the smallest number of presses that solves it.