java -jar PetitPrix.jaror, in Windows, double click the corresponding icon (provided you have installed JDK 1.2 or later in your system).
When you move the mouse over the available positions, a grid of squares indicates the available positions in the next turn. You can also use the keys on the numeric pad to select the position.
After you have clicked an available position (or pressed enter if you are using the keyboard), your car moves to the new position and the velocity vector is updated. If you have no available position where to move, your car will crash and stay immobile as many turns as were your speed at the moment of impact. After that, you can continue the race by starting from standstill.