How to play
You get a square panel of lamps, some lit and some dark. The goal is a completely dark panel.
Pressing a lamp toggles it and the lamps directly above, below, left and right of it. A lit lamp goes dark, a dark one lights up. So one press in the middle of the panel changes five lamps, a press on an edge changes four, and a press in a corner changes three. Diagonal neighbours are never affected.
The bar above the panel tracks three numbers: Moves (how many presses you’ve made), Best (the fewest presses that can solve this panel) and Lit (how many lamps are still on). A clock starts with your first press.
Buttons
- New puzzle deals a fresh panel at the current difficulty.
- Undo takes back your last press and its move.
- Restart puts the panel back the way it started. Your move count keeps running, so a restart costs you the chance of a perfect score.
- Hint presses one lamp for you, chosen from a shortest solution of the panel as it stands. It counts as a move and is recorded as a hint.
Pick a level with Easy, Medium or Hard 7×7; changing level starts a new puzzle. You can also play with the keyboard: arrow keys move between lamps and Enter or Space presses one.
Levels and the “Best” number
Every panel is built by pressing lamps on a dark board, so it can always be switched off again. The game then works out the shortest possible solution, and that count becomes Best.
- Easy is a 5×5 panel made from three to five presses, so you can often see the answer by spotting the crosses.
- Medium is also 5×5 but scrambled by pressing about half the lamps at random. Best is always at least five.
- Hard 7×7 scrambles a bigger panel the same way.
Finish in exactly the Best number of moves without any hints and the end screen calls it a perfect solve. Otherwise you’ll see your presses next to the best possible, your hints and your time.
A curious detail: on the 5×5 panel, any solvable pattern has four different sets of presses that clear it, and the game picks the smallest. On 7×7 there’s only ever one set, so Best is simply its size.
Strategy
Two facts make this puzzle far less random than it feels at first.
Order doesn’t matter. Pressing A then B gives the same panel as B then A. And pressing a lamp twice cancels out completely. A solution is therefore just a set of lamps, each pressed once. If you’ve pressed something twice, you’ve wasted two moves.
You can clear everything but the bottom row mechanically. This is called chasing the lights:
- Look at the top row. For every lamp that’s lit there, press the lamp directly beneath it, in the second row. That press turns the top lamp off and doesn’t touch the rest of the top row.
- Now do the same for row two, pressing in row three. Carry on down the panel.
- When you reach the bottom, only some lamps in the last row will be lit.
The leftover bottom-row pattern tells you which top-row lamps to press. Make those presses, then chase down once more and the panel goes dark. Working out the right top-row presses for each leftover pattern takes some experimenting; if you get stuck, a single Hint often shows you the opening press.
Chasing always works, but it rarely matches Best. For a perfect score, try these instead:
- Look for plus signs. Five lit lamps in a cross shape vanish with one press in the centre. On Easy, the whole panel is often a few overlapping crosses.
- Read overlaps. Where two crosses share lamps, those lamps are dark again (pressed twice). A pattern with a strange gap often means two presses next to each other.
- Don’t chase the Lit counter. A correct press often lights more lamps than it turns off, especially early on. Fewer lit lamps doesn’t mean you’re closer to the end.
- Use Undo to test ideas. Since undoing costs nothing in the final count, you can try a press, look, and step back.
If you enjoy puzzles with a provable shortest answer, the Sliding Puzzle and Tower of Hanoi are two more classics to try.
If you enjoy Flip Lights, try Futoshiki or Gumball Pop next.
