Crystals is a small game of logic and deduction. The objective of the game is to find out where in a grid crystals are hidden. You can do that by firing laser beams into the grid and observing the refraction patterns.
A laser beam may cross the grid without being disturbed by a crystal, it can get refracted by a crystal and leave the grid somewhere else, or it can get absorbed by a crystal if it hits the crystal head on. You win the game if you are able to identify all the squares which hide a crystal, without failing.
There are several variations on the basic game. You can play on different difficulty levels, you can play on a custom board, you can play with or without a timer, you can play with or without knowledge of the number of crystals hidden, and you can play predesigned layouts, which are often a quite tricky. The game can also be used to create your own designs.
The game contains an extensive help file, and an introduction to help you start playing.