You must collect all the colored perls, but in the right order, or the floor that disappears under your feet will prevent you to continue. Usually, you'll have to leave the red perls to the end. If you do it well, you'll be able to pass to the next level, or go back to a previous one, by following the arrows that appear at the end of each level.
Arrow keys to move, space bar to restart level. Mouse click for special actions.