Fire + Fire = 3x combo count
Wind + Wind = Shurikens on bamboo & street lights
Gold +Gold = 3x gold count
Thunder + Thunder = Shock wave which kills nearby zomblings
Wind + Gold = 1 gold per zombling hit
Fire + Thunder = Combo will not reset until effect wears off
Gold + Fire = Random 3:1 ratio for combo & gold counts
Thunder + Wind = Shurikens kill all except Berzerkers
Gold + Thunder = 1 gold per kill, even on bamboo & street lights
Wind + Fire = 3x combo per zombling hit
Any 3 = Obtain 4th automatically