Prism

A light puzzle with one rule and no clock.

A lamp stands on the bottom row and fires a single beam straight up. Mirrors sit in its way at forty-five degrees, and each one turns the light a quarter turn — left or right, depending on which way it is set. The receiving stone is somewhere on the top row. Tap the mirrors until the beam reaches it.

Every board keeps a par: the smallest number of turns that solves it. That number is not a designer's guess. It is found by trying every combination of mirror settings before the board is ever shown to you, so when the board says PERFECT it means there was no shorter answer. On all twenty-four boards there is exactly one — every mirror has to end up right.

Twenty-four boards, five columns wide and nine rows tall. The first eight put two mirrors in front of you, the next eight four, the last eight six, and blockers stand in the squares the light must not take. Each board is built backwards from a beam path that already works, so all of them can be solved — and a separate pass re-checks every one by brute force before it ships.

There is no timer, no lives, no energy, no daily streak and nothing to wait for. Any board can be reset as often as you like, and the level list remembers which ones you have finished.

Fully offline. No account, no ads, no purchases and no data collected: the app makes no network requests at all and works in airplane mode. The list of boards you have solved is written to your own device and stays there.

The interface is in English.

Credits
Wood texture from "RPG GUI construction kit v1.0" by Lamoot, used and modified under CC BY 3.0.
https://opengameart.org/content/rpg-gui-construction-kit-v10
https://creativecommons.org/licenses/by/3.0/
Droid Serif by Steve Matteson / Ascender Corp, licensed under the Apache License 2.0.
https://www.apache.org/licenses/LICENSE-2.0