At the title menu you can press the tabulator key to open a command prompt, where you can input the codes mentioned below.
Secret
There is a bit of extra stuff in the game. To access it, defeat the boss of the fourth world but do not leave the level; instead let the cannons shoot you. Well, you can also take a shortcut and enter "drdrd" at the prompt mentioned above.
Cheats
More codes that work at the prompt:
- "booya": infinite lives
- "12345": access all worlds
The catches: Cheating disables permanent save of progress, and even the ending. You cannot have both cheats active at the same time. The cheats will automatically become inactive when you return to the title menu.