You are in control of a circular heap of planets with a dead gray planet at its center. During the game, planets appear from all directions moving towards the center and sticking to the heap. Line up 3 or more planets of the same color to make them pop and vanish.
The heap can be rotated using [LEFT] and [RIGHT] arrow keys, which allows you to change where the planets stick. Gray planets will not pop and vanish if you line three or more of them up. But they will burst if the planets next to them pop. Planets stuck in the heap for too long will turn into dead gray planets. The heap grows until it crosses the circular heap boundary at which point the game is over. Good luck!