The Nintendo DS version of "Monsters Vs Aliens," based on the movie of the same name, offers younger players a series of adventure-themed levels featuring the movie's characters. One level features the movie's mad scientist character, Dr Cockroach, as host of a refraction-based puzzle that must be solved before the level can be passed. Solving the puzzle is deceptively simple, but requires careful placement of the mirrors given to you.
Drag a mirror directly under the green circle closest to the switch.
Place a mirror on the square to the left of the switch.
Place the last mirror to the right of the green circle closest to the switch to complete the light's path over all the green circles.