is a 20-level puzzle game; on each level, there is an assemblage made of colored blocks, and numerous balls of various colors are lazily floating around it, bouncing off walls and blocks. By clicking and dragging a selection square around one or more balls, the player makes these balls succumb to gravity and fall--on the way down, they erase all blocks they touch, provided the block is the matching color. The goal on each level is to erase all the blocks (except for black blocks of "stone" that are impervious to almost all balls).
There are two special ball colors. White balls can erase any block color; red balls do likewise, and they can also erase the "stone" blocks.