Your job as a robot is to guide the ball launched from the blue portal into the orange portal. You cannot interfere with the ball directly — instead, place reflectors and other gimmicks to steer it toward the goal. To clear a stage, count the ball until the number displayed at the top reaches zero. Learn the properties of each gimmick and maximize your count as efficiently as possible. Don't worry — every time a new gimmick appears for the first time, there's a dedicated tutorial stage to introduce it. Each one is carefully crafted to ease you in :)