Pendulous

On the bonus playground (marked "B" on the level select screen), you're free to play around without any danger of being hurt, but there's no obvious exit. If you touch the topmost anchor, it says, "No secrets here...nope, nope." This is a hint. If you attach to every anchor in the playground AND touch at least one of the bumpers, then the game says, "You're at the top of your game, Operator." Return to the top and the pipe will have pulled back revealing the exit.