AFE-33A-19E Kill 1 enemy to go to next level
FAB-CEE-4C1 Infinite hearts
3E8-39F-081 + 138-3AF-D5E + 008-3BF-E6D Start on round 20
3E8-39F-081 + 278-3AF-D5E + 008-3BF-E6D Start on round 40
3E8-39F-081 + 3B8-3AF-D5E + 008-3BF-E6D Start on round 60
015-5CE-E66 Start with 1 heart
065-5CE-E66 Start with 6 hearts
095-5CE-E66 Start with 9 hearts
C97-8AE-E66 No big bubbles appear
FA5-58E-4C1 + FAB-46E-4C1 + FAB-63E-4C1 Run into 1 enemy and you remain invincible 
for the rest of the game