throw colored marbles against each other. If two marbles of the same color make contact, they merge and upgrade to the next color. Your lifebar diminish with the number of balls on the field. If you lifebar is empty, you enter in a sudden death mode, and your last ball must save you by removing some balls.

Pro-tips :

dark and grey balls do more damage to your life bar, so avoid keeping to many at the same time
score system depend on number of rebound before merging and on balls colors
a usefull technique is to quickly throw two dark ball and make them merge at the first collision
try to avoid exploding pink balls as long as you can, you can expect making more point in the final explosion