Though the iPhone version is about a month old, Digital Chocolate has recently released the iPad version of their physics-oriented, puzzle’esque racing game, Underground 3D Rollercoaster Rush HD. If the name sounds familiar, that’s likely due to its base stemming from an older Digital Chocolate title, New York 3D Rollercoaster Rush HD. However, where direct multiplayer held in the older app may be lost, the newer game takes a different social approach by joining the OpenFeint network.

Like its predecessor, Underground challenges players to race on, quite possibly, the worst designed roller coasters ever. Wrought with steep drops, collapsing tracks, and half finished loops, players use physics to try and complete each level in the fastest time, whilst trying to earn the highest score possible. These bizarre tracks, combined with the fast-paced nature of a racing game makes for a very curious marriage of features that could be best described as a “racing-puzzle game.” Though, it can be frustrating at times, it still makes for a fun creation, and with direct social integration, gives the game an extra level of depth the previous Rush title did not quite have.

Though the premise of the game is a bit different from most games, the overall play is actually quite simple. Players a presented with a very unsafe underground roller coaster, with the sole objective of reaching the end – preferably in one piece. In the more unique mode to Underground — “Underground Mode” — users control a single coaster car that the engineers never locked into the track. Basically means that every incline, dip, or flip can and will send you careening off course.

Controls on the iPad are simple enough, as players touch a pair of sizable arrows to move left of right and a pair of others to rotate forward or backward (though you can turn on the accelerometer to control through tilting the device). The idea is that every time one of these obstacles sends the car off in some, whacked-out, direction, the player must use the controls to reorient it so that it lands wheels down, and, frankly, it’s almost like a puzzle — trying to figure out what direction to rotate, how fast to go, and so on. Failing to do so will result in the vehicle either landing on its roof or plummeting into the void beneath the track.

There are a ton of twists and turns to deal with, so it takes a good eye and a lot of practice to prevent either of these results from occurring, and one might think it frustrating. Surprisingly, it’s not that bad, because neither causes the player to fail. Each track actually has a number of check points to hit, and should the user get stuck or fall, they merely restart at one of these locations. That isn’t to say there is not penalty for failure, however, as the objective is to get the fastest time possible, and the clock does not stop or reset for redos.

After each level, players earn a final score and star rating based on how they did. With the rating alone, an extra level of longevity is added for players that like to earn achievements. Furthermore, considering the speed in which cars move, getting those top ratings and scores will prove most difficult.

As a matter of fact, the latter can be even trickier as there are a myriad of stunts that can be performed to boost points earned as well. As if reaching the end weren’t hard enough sometimes. Players can do flips, catch air, and any number of other “acrobatics” in order to increase their score, and in turn, add a significantly higher level of challenge.

Further challenge is also layered into Underground with OpenFeint. Expectantly, this means a truck load of achievements to earn and share, but since the game is oriented around high scores and fastest times, the competition that comes from leaderboards will be most attractive to many players. Unfortunately, the Bluetooth, head-to-head multiplayer from the New York title has, apparently, been lost.

Underground 3D also has a Classic Mode that is worth mentioning. Here, players control a full three cart coaster through each level. However, since the coaster is three cars long, the rotation element doesn’t really do much, and it really just comes down to speed. Compared to Underground Mode and the single car, it is significantly easier, and very hard to fail. Likely, it’s just there for users to mess around with a bit.

All in all, Underground 3D Rollercoaster Rush HD is a pretty fun game. It’s hard to say how it’s almost puzzle-like racing will appeal to players, but if the previous New York title is any indication, with its generally high user approval, it ought to do well. That said, the game runs $2.99, but for those on the fence regarding its value, there is a nice free version to sate the appetite (which also incorporates OpenFeint). Overall, the game is an amusing addition for iPad owners, and while it doesn’t feel “great,” it is still better than most.