In the beginning, you can only drive one vehicle, and it has pretty mediocre stats. But as you advance in the game and collect coins, you can buy different ones and also upgrade the ones you already have, improving their speed, grip, and tilt stats.
The controls in MMX Hill Climb are pretty typical: the brake is on the left of the screen, and the gas pedal on the right. Be careful when pressing on the pedal, though, as if you accelerate too much your vehicle can turn on its head and crash. If you go too slow, though, you might run out of gas instead. Decisions, decisions, eh.
Visually speaking, MMX Hill Climb is a spectacular game. The gameplay can be hard, but it's still a lot of fun. You'll have trouble completing even the first track, but that's actually what makes it so entertaining.