"Control a mechanical arm to catch and throw monkeys against platforms to free the islands of them."
In Cactus Bruce you control a mechanical arm with which you can catch and throw monkeys that are in different parts of the island to break the platforms that support them. If you are able to get them into the water, you get points and extra help to make the job easier.
The monkeys don`t make it easy for you. They defend themselves by throwing coconuts that you have to intercept before they hit you and you lose a valuable life.