Laser and mirror logic puzzle
How to play PRISM
PRISM is a free daily logic puzzle you play in your browser. A laser fires from a fixed emitter and travels in a straight line until it hits a wall, leaves the grid, or is bent by a mirror you place. Tap cells to lay down angled mirrors and route the beam through every target ring on its way to the receiver - using as few mirrors as you can from a strictly limited budget.
Play PRISMHow to play
- 1Watch the beam leave the emitter and travel in a straight line.
- 2Tap an empty cell to place a mirror; tap again to flip its angle, and once more to remove it.
- 3Route the beam so it passes through every glowing ring before reaching the receiver.
- 4You can only have so many mirrors down at once - remove one to free up the budget and try a different route.
- 5The beam can never cross a cell it has already passed through, so plan bends that don't double back on themselves.
Tips and strategy
- Work backwards from the receiver as often as forwards from the emitter - the last bend is usually the easiest to pin down.
- A mirror only ever turns the beam 90 degrees, never straight through or back the way it came - use that to rule out angles fast.
- Removing a mirror is free, so experiment. There is no penalty for trying a bend and undoing it.
- Fewer mirrors than the budget earns extra stars, so once you find a working route, look for a shorter one.
Frequently asked questions
Is PRISM free to play?
Yes. PRISM is completely free to play in any web browser, with no download and no sign-up required.
What is the daily challenge?
Every day at midnight PRISM generates three new boards that are identical for every player in the world. Clear them and share your mirror count with friends.
Is there an endless mode?
Yes. In endless mode the boards keep growing and a shared mirror bank only partially refills after each one - spend mirrors wisely, because the bank eventually runs out.
Why can't I place a mirror on some cells?
Mirrors can't sit on walls, the emitter, the receiver, or a target ring - only on plain empty cells the beam can freely pass through.