sentences:  A level is cleared when there are no more passengers to pick up, and the player then moves onto the next level which is a different layout, bigger or smaller with more dead ends.Also, the bonus stations appear more frequently and, on later levels, one or more Crazy Trains will be on screen at the outset.If the player creates a closed loop of track and rides on it for several seconds, a "Loop Sweeper" appears which moves around the loop behind it.