Kill 3000 enemies
Kill 2500 enemies
Fully upgrade two of the characters
Unlock the third character
Unlock all items
Beat the 4th level
Unlock a new item
Beat the 3rd level
Beat the 2nd level
Kill 1500 enemies
Fully upgrade one of the characters
Unlock a third character
Kill 750 enemies
Unlock a new character
Beat the 1st level