Level select (Japanese version):
Press Left or Right at the title screen to change the starting level number in the lower left corner of the screen.
Invincibility (Japanese version):
Pause game play and press X. The word ‘Muteki’ will appear on the life gauge to confirm correct code entry. Note: ‘Muteki’ is ‘Invincible’ in Japanese.
Successfully complete the game under the Easy difficulty setting without using any continues to get two bonus credits for the Normal difficulty setting. Successfully complete the game under the Normal difficulty setting without using any continues to earn four extra credits for the Hard difficulty setting (if you began with the Easy difficulty setting), or two extra credits otherwise.
Select hard mode in ‘Level’ at the ‘Set Up’ screen. Start the game and finish it. After the credits, the game will begin again, but at a higher difficulty. Finish the game again. In the final sequence of credits, the message ‘SEE YOU LATER IN AXELAY 2’ will appear in the upper right corner of the screen.