Unlockables give this jump-physics Flash game some pretty strong replay value. I spent at least 30 minutes tricking out my cart and practicing midair handstands.
The object, bobsled your shopping cart down a hill and then up a ramp, collecting dollars for the distance, height and difficulty of your jump. Use them to buy upgrades such as better wheels, rocket boosters, and ride-along groupies, all of which alter the trajectory and length of your jumps. While you have unlimited lives, crashing will kill any groupies onboard, and you'll have to go back and "buy" them up all over again.
Protip: There doesn't seem to be any performance bonus to hopping in the cart (up arrow) when the game prompts you to do so. And with an engine-equipped cart, your afterburner kicks on as soon as you hop in. Just hold down the run key at the start as long as you can; the guy will hop in automatically, and your jets will stay on longer through midair.
Shopping Cart Hero [Monkey Want Banana]