Cheat mode:
Hold A and power on the Genesis. Release A and press Up, Down, Left, Right, A, B, A, C, B at the title screen. Two additional options will appear on the configuration screen. Enable "Muteki" for invincibility. Use the "Window" option to adjust the screen size.

Level skip:
Press A + Start to jump to the next level.

Slow motion:
Pause game play and rapidly tap B.

Change color:
Press C + Start. Note: This may not work in later versions of the game.