For a long time, it's been one of my (many and unrealised) gaming ambitions to come up with a system for running a game which I call Risus Elementalists. The concept is simple: it's a very high fantasy "fantastical" sort of setting which is mostly based around this sort of tonal palette, and the PCs are elementalists. You get four magical stats. The magical stats have to be Earth, Air, Fire and Water.
What I have so far is as follows:
When you want to cast a spell, you roll the requisite number of dice and describe what you want to do. If you get one or more '4's or above, you succeed. The more '4's the better. You have to be able to describe what you are doing in a vaguely plausible way: "I summon forces of fire to blast my enemy" is fine. "I summon forces of fire to telekinetically move the object across the room" isn't really.
Combat between elementalists is like rock, paper, scissors. Fire beats earth because it can scorch and melt it. Earth beats air because earth is immovable. Air beats water because water is movable. Water beats fire because, duh. If magical combat occurs, both of the Elementalists note down on a scrap of paper what element they are using. On the count of three, they reveal it. If one has fire and the other earth, the one with fire wins automatically - and so on through the elemental "oppositions". If, however, the two of them have come up with non-opposed elements (for example, earth vs water) they roll their respective abilities and the one with the most successes wins.
Everything else is done through role playing.