Press * to pause game play.
At the title screen push: Up, Up, Right, Down, Up, Left, Left, Up
At any time during the game, pause and push Down, Down, Up, Right, Right, Right, Left, Up
Mr Do can shoot through tunnels that are separated by very thin walls.
Collect the prize in the middle of the screen while the "Extra" apple at the top of the screen is on a red letter.