Wetrix was originally released for the Nintendo 64, the pieces shapes are like tetris the "L," the simple square, the helpful straight line, and the multi-purpose "T." But the mechanics of Wetrix are quite different. The playing field is an isometric square. Each piece you drop raises the landscape to create ridges of the appropriate shape. You'll need to quickly build canyons to prepare for the inevitable water pieces, which you'll need to drop within your makeshift storage bins in order to contain the flood. Your goal is to let as little water as possible drip from the sides.
That wouldn't be so difficult were it not for the other elements that conspire to hinder your progress. The water acts realistically, dripping over the sides of your ridges when a particular basin is full, so it's helpful to create a series of high walls and deep valleys. There's no safety in this strategy, though, because as your walls get higher, the threat of a devastating earthquake (which sends the whole map topsy-turvy) grows greater. Pieces that lower your ridges help in this respect, and fireballs occasionally appear to evaporate the water in selected areas without penalty. There are also bombs, which put a hole in the map, causing any water in the area to rapidly drain, and ice cubes, which freeze any water they touch, effectively turning water to walls for a short period of time.
Not only must you try to keep watertight, but you're also going for a high score. You get bonuses based on how many lakes (enclosed areas containing water) you have built, and deeper lakes will earn a rubber ducky, which floats and quacks on the water, multiplying your score when present. It's maddening, and addictive.