"Riding a bike is fun. Riding a bike over obstacles is more fun. Jumping through loops on fire 200 meters in the air is fun. Falling off a bike is not fun. Watching someone else fall off a bike is fun. Trials HD is game about doing just that. You get to be a biker on a stunt bike, and not have to worry about any physical harm.
The concept of Trials HD is very simple. You control a bike and its rider's balance. The bike moves along a 2D plane in a beautiful 3D world. You accelerate the bike and lean the rider forward and backward. Realistic physics takes over and this allows the bike to jump, wheelie, do backflips and ultimately crash in a thousand different ways."