The third is a pyramid. You do have to travel back and forth between them. Warning a few hints that may spoil the game for some players. When playing with planets, remember there are nine of them. Teeth in a disc can move.
Rainbows are very pretty.
Grass can hide many things. Before you start playing this game, download the patch from the Dreamcatcher web site. The bug will prevent your progress though the game. You will only get the benefits from the patch from a new game. If your cursor is not in the center of the screen, you start slowly spinning in place.