In the game the player collects good things like health from the hospital, ammo from the pharmacy and attitude from home.
The player then faces monsters representing the side effects of cancer - a fever monster throws fireballs, a giant, evil chicken represents chicken pox and a robot called Robarf hurls a green gooey mess.
Ben said: "I just want children to learn what the medicine is doing to their body and how it's helping it," he explained.
"And I hope that they'll learn not to give up, to stick with it or you won't make any progress. And to just hang in there and have fun."
To play Ben's Game, go to www.makewish.org/ben where you can download the game, as well as read messages from Ben and find out more about the project.