On the title screen, when the Push Start Button flashes, enter Up, Down, Left, Right, B, A. If done correctly the Gleylancer logo will turn gold and the Mania setting will be available in the Options menu.
When "STAGE 1 START" appears, press B, B, C, A, Up, Down. The screen now functions as a stage select.
While the game is paused, press Up, Down, A, B, C, Left, Right, C, B, A to add one life. This code can be entered more than once for more lives.
While the game is paused, press B, A, C, A, Down, A, C, A, Right, A, B, Up, Right, Up, B, Up, Right, Up, Down, A. This opens a menu with lots of options, including MUTEKI (invincibility).