Switch Off in Games by Zaweba: fifty bulb puzzles to solve
Switch Off in Games by Zaweba has fifty 5 by 5 bulb puzzles where each press flips a bulb and its neighbours. Turn them all off and aim for gold.
Twenty five glowing bulbs sit in a 5 by 5 grid, and you want them all dark. That sounds easy until you press one. Switch Off is a set of fifty bulb puzzles on the Puzzles shelf of Games by Zaweba, and every press does more than you might expect.
What a press does
Pressing a bulb flips it, on to off or off to on. It also flips the bulbs directly above, below, left and right of it. Diagonals are untouched. So one press changes up to five bulbs at once, and turning one bulb off often turns its neighbours back on.
Your aim is to turn every bulb off.
Levels, par and gold
The fifty puzzles come in sets of ten levels. Each level has a par, the fewest presses that will solve it. Solve a level in exactly that number and you earn gold. The challenge is to clear each set with as few presses as you can.
Click a bulb to press it. Use the panel to pick a level, or press Left and Right to change level. Press Z to undo a press, R to restart the level, and H for a hint.
Two useful facts
Two properties of the puzzle make it far easier to think about.
First, the order of your presses does not matter. Pressing A then B gives exactly the same board as pressing B then A, because each bulb simply flips once for every press that touches it.
Second, pressing the same bulb twice undoes itself. So in a good solution, each bulb is pressed either once or not at all. That turns every puzzle into a question of which bulbs to press, not when.
Chasing the lights down
A well-known method works on any solvable 5 by 5 board. Look at the top row. For every bulb that is lit there, press the bulb directly below it in the second row. That turns the top row dark. Now do the same for the second row, pressing in the third. Carry on down to the bottom.
At the end, only the bottom row may be lit. The pattern left there tells you which bulbs in the top row to press before you start chasing again. You can work this out by experiment and undo, or press H for a hint about where to begin. The second time down, the lights should all go out.
This method always reaches a solution, but not always the shortest. To match par for gold, look for presses that cancel out, since a bulb pressed twice in your sequence can be left out altogether.
Getting better at it
Once you know the chase method, try solving a level by eye first, looking for a cross shape of lit bulbs that one press will clear. Many of the earlier levels are built from a few such crosses.
Restart freely with R when a level gets messy. There is no penalty in starting again, and a clean run from the beginning is often quicker than untangling a muddle.
In the app
Switch Off sits on the Puzzles shelf of Games by Zaweba with Slide Puzzle and Marble Solitaire, where a set pattern has to be reached through careful moves. Its ten level sets make it a good game for steady progress, a level or two at a time. Press Esc to pause and F1 for the rules.
