A room with four colourful candles and an equally colourful floor.

Each time you step on a coloured tile, the candle of the matching colour lights up, or goes out if it’s already alight.  The exit only unlocks when all four candles are burning.

Here’s a simple procedure for escaping from this room.

Walk over to the exit.  If it’s unlocked then well done!  You’ve solved the puzzle.

If the exit is still locked then choose one of the candles that needs to be lit, and walk until you’re standing on a tile that matches the candle’s colour.  Then walk back to the exit following exactly the same path you came by.  The candle you chose will now be alight while the other candles are the same as before.

Repeat this until all four candles have flames.