If there is a bug when you play, and the cars don't move, then click the green flag again. It is a 2 player race. For blue car, you use arrow keys to move, for red car you use wasd. The goal is to collect the most amount of gems before the timer runs out, each time you collect a gem, it adds 1 second to the clock, try to avoid snowballs and you can push the other car of the track. If you hit the snowball or go off track, you will spin out of control for a bit.
DONT FORGET TO CLICK THE GREEN FLAG TWICE! The book "Coding Games in Scratch" helped me