Infinite continue
Up, Zoom1, Right, Zoom2, Down, Zoom3, Left, Zoom2, Up, Zoom1.

Wizard mode
Press Z, C, Z, C, [Up], [Down], [Up], [Down], [Left], [Right] at the main menu. Game play will be faster in this mode.

Do all the following codes at the difficulty menu screen. Depends on how you config the keyboard. Press [f6] key for your current keyboard config. (eg. Zoom1 is default to "A" key)

No dragon
Press [Up], A, [Right], A, [Down], A, [Left], A, [Up], S, D during game play.

Invincible mode
Turn Left, Turn Left, Turn Right, Turn Right, Up, Down, Left, Right (It should display "Invincible Mode" after you've type it. Please note the Turn Left key isnt the same as the Move Left key. If you can't make it working, try config the Turn Left key to "Q" and Turn Right key to "E". Then type Q,Q,E,E,Up,Down,Left,Right should be okay)

Stage Select
Up, Up, Down, Down, Left, Right, Left, Right, Zoom1, Zoom2, Zoom3.