From the title of the game itself, I bet that you have already a clue on how this game goes. As you can guess, the truck itself is unbalance and will easily fall on its back. Though the terrain adds some reason why the truck would tip over, the truck is also lightweight that it can easily fall on its back.
The object of the game is to get to the finish line as fast as you can and in one piece. Since there are many ramps in the game, you need to balance your truck from left right to keep it from crashing.