Write RUNCHEAT to get unlimited lives.

To enter Cheat Mode, first pause the game (space).
When you have paused, write DSIMAGIC and then space again. Now, catch the little thing that falls down. Now you can summon things with these keys:

B - Opens door and gives you bonuspoints.
C - The ball gets stuck
D - The ball will split into 3 balls.
L - Laser 
P - Extra player
S - Slows down ball 
F - Transports you to the last level 
Enter - Next level