I've added a stamina meter, as well as slowing down the speed at which the work meter goes down. After deciding that the main game wasn't enough, I've added a second game. In Shooter, you must protect yourself from falling rocks, and pushing the walls back so they don't crush you. Every 5 seconds, your bullet speed gets faster, but also the speed that the walls move in, and the time in between rocks.

I'm thinking of adding a third game, in which you are trying to survive as long as you can in a room in which the floor under you is constantly falling.