Kill 5000 enemies
Kill 10000 enemies
Complete level 5
Complete level 10
Complete level 15
Complete level 20
Unlock all levels for all towers
Unlock all levels for all special attacks
Win a level without losing HP
Use 3 special attacks within 5 seconds
Use a 6x supercharge
Kill 10 enemies at once
Kill 20 enemies at once
Survived 50 events
Set fire to a gas drop