Here, the huge amount of stored water causes a score-multiplying rainbow to appear. Too bad that descending fireball will evaporate it all. Unlike water bubbles, you can't control the weather. This means your entire landscape must be enclosed to prevent rain from leaking out. And before long, bombs and fireballs will drop from the sky.
Bombs blow up an entire chunk of landscape, creating a hole in the bottom where water can leak out.
Fireballs evaporate lakes of water, and then there are the special events. You'll have to deal with earthquakes, rainbows, rubber ducks, mines, smart bombs, ice cubes, and more. There are a bunch of gameplay modes to mess with, including a pretty darn fun multiplayer mode. Single player modes include classic, pro, practice, challenge, and handicap. I personally found classic mode to be difficult enough for me, and spent most of my time with that.