If you are looking for different concept of game, tricky but exciting and also educational, try this one.
Rather than controlling main character, who moves alongside predefined path, you are controlling his obstacles. By tapping on screen, you move the joint of four rods, therefore resizing holes on them, so the main character called Bob can safely pass through. May seem complicated, but once you get used to the concept you gonna love it.
Paths you are about to cross are called polar curves. So there's a way to learn their names, from Kepler's folium to Scarabeus, from Neoid to Fermat's spiral. Some of them are well known to mathematicians, others were invented during the course of this very game's development.