Aqua Aqua gives you a square of land (viewed from a corner - think Populous) onto which you must drop blocks of 'uppers' and 'downers', Tetris-style, to create lakes. You want to do this because sometimes you don't get a block but a quantity of water, which you have to drop into a lake. Sometimes you get a fireball, which you can drop into a lake to evaporate the water. This is desirable because if a lake overflows and the water runs off the edge of the land it collects in a gauge at the side of the screen. When the gauge is full, you lose. Simple.
Of course, it's many years since a game was allowed to be _that_ simple. So there are complications: bombs, which punch holes in the land; earthquakes, which demolish your lakes if the land gets too mountainous; and a wide range of arbitrary and non-intuitive bonuses. You can't ignore these, as if you want to see the whole game you occasionally have to score a certain number of points within a time limit to avert disaster. It's...