I have been working on a small simple brick breaker game that goes on forever. As time passes the bricks move down and a new row appears the rate that this happens speeds up over time. If enough time passes or you clear the game of bricks a boss battle triggers. After you beat the boss the level refills with bricks and the rate that they move down continues to increase. You can go to an upgrade shop to increase the effectiveness of the power items so you can last longer and longer.