Bubble Train as the name suggests is a train of bubbles travelling along a track where the last carriage is the driving force instead of the front one. The bubbles come streaming along the track trying to reach the end of the line. You are equipped with a bubble firing cannon, where you fire bubbles into the trains. When there are 3 or more carriages of the same colour they explode and the train shrinks. So you must blow up all of the carriages in all of the trains before any train reaches the end of its track.