You get to drop balls from certain positions.
You can aim or choose the drop point in many cases.
The balls interact with the environment: glassware, supports, possibly moving platforms or obstacles.
Physics matters: timing, angle, force, obstacle clearance.
Your goal is to spill all the liquid from the glasses. You do this by using the balls: drop, throw or position them so that they hit the glasses (directly or via bouncing or rollovers) and cause the liquid inside to spill out.