If you’ve ever played Tetris, you know that the game has a clear goal: to prevent the blocks from stacking up to the top of the screen for as long as possible.

You accomplish the goal and win, or you lose and start all over again.

Other games, like The Sims, don’t have a clear goal. Its sole purpose is to continue the play. You can build houses, find a job for your Sim, and even drown him at the pool…but the game per se never ends — only when you turn off the computer.