A bunch of kids find an advertisement for a rocket powered swing, that costs $50,000. Of course they need it, but being children they don't have the money. But the idea is settled upon to earn money by jumping off the swingset they do have. Jump off the set earning more money for flips, distance traveled, time elapsed, and bouncing off birds. Use money earned along the way to upgrade your swingest and increase the abilities of the children.