Swamp Monsters

An alien swamp is infested with monsters. You control a robot sent in to destroy them. The only way to do that is to move the stepping stones in the swamp so that the monsters will fall in and drown. However, the swamp monsters will try to destroy the robot first.

There are three kinds of monsters living on the surface and a fourth kind, the lake monster, which cannot be killed. The lake monsters are normally no trouble provided the robot keeps moving.

The red monsters are the least intelligent and are worth 100 points for each one your manage to drown. Yellow monsters are worth 200 points and white monsters 300 points. The white monsters may mutate into Lake Monsters when they fall in the water; the only way to prevent this is to drop a stone on them before the change starts. If you succeed, it is worth 500 points.

When you destroy one screenful, another will appear. The robot only has a limited power supply, how quickly this is used up depends on how many stones it is carrying. If it tries to carry more than two, then it will sink. You start off with three robots and will be given extra for each 5,000 points.