Plug in the paddle controllers. Now, press both buttons, and your tank will speed up.
Select game 9 and start the game like normal. Rotate the tank on the left 180 degrees and fire. If done correctly, the shot will bounce around the screen and hit the right tank. Both tanks should fly approximately three screens to the left before stopping.
Keep a hold of Reset on the console and the fire button on the joystick to make your tank shoot to the other side of the screen.
Select game 9 and start the game like normal. Then rotate the tank that is on the right 180ยบ, then fire. If it's done correctly, both of the tanks should switch positions.
Place your tank just to the right of the top left corner and fire into that corner. The shot will leave the screen and re-appear from the top right corner.