Crystal Mine is a relaxing game, without any headache, whose goal is to collect a minimum of 80 crystals in less than 8 strokes. By touching an unenclaved crystal (you will recognize it, it shines), you collect all adjacent crystals of the same color, and all other unenclaved crystals of the same color.
Bonuses will be there to support you but will become increasingly rare as you progress through the levels.
Good luck!