Pebble Universe [iPhone]
When the soot monsters explode, they hurl out more debris - use this to your advantage when attempting to clear out the entire stage.
You only need to slay the Soot King on each level to complete it, but killing every single monster on a level will earn you a bonus.
When starting a new level, always use your first few attempts to experiment. Get an idea of how the environment affects the movement of your pebbles before mounting any serious challenge.