To their credit, developer Idol Minds has managed to squeeze several play modes out of the game's simple play mechanic. The single-player game includes the standard "bounce around and earn points" mode as well as Clown Toss, which plays exactly like the original's Mime Toss, only instead of tossing white-faced mutes through glass, you're tossing clowns into explosive crates. Another is Hot N Cold, where you try to find a specific exploding teddy bear hidden among hundreds scattered around the park. Before launch, you can get a general direction of where the target bear is by viewing the map. Bears closer to the target are red while more distant ones are blue. Of all the modes available, Hot N Cold is probably the best - mostly because it has an actual goal beyond building up a score on what is essentially one big crapshoot of a mechanic.
PAIN: Amusement Park also adds a handful of multiplayer modes. TRUMA is a variation of HORSE where players try to match each other's launches. The mode is expanded in Call Da' Shot, which is a bit like the old Jordan vs. Bird "...nothing but net" McDonald's commercial. Opponents call a trick shot and bet on whether or not the player will be able to make it. After two tries, the person who set up the course must complete it, or risk losing points. With the right people, Call Da' Shot can be fun, though you'll have to gather up your friends if you want to try it out since there's not online multiplayer.
The only really interesting mode is PainLAB. Each week, new mini-games are uploaded to the PainLAB, which acts as a testing ground for new gameplay ideas that could possibly turn up in future expansions.