Infinite Undiscovery Cheats

Unlockable: Tough Difficulty

Finish the whole game with normal difficulty level for at least once and then you would be able to unlock the hard difficulty settings.

Ikaruga Cheats

Unlockable: Infinite Continues

To get an infinite amount of continues, register eight hours of total gameplay. Keep in mind that as you go up in hours (from one, to two, to three and so on), you’ll unlock more and more continues until you hit eight hours, which will unlock infinite continues.

Unlockable: Prototype Mode

To unlock a new mode in the game called Prototype Mode, beat the game once through in its entirety.