Thank you for playing my game! I'm glad you liked it. I agree 5 bullet and especially lighting 5 were much weaker than fire and ice, this is something I figured it few days after deadline through playtesting,
Also cool insight in game's development, in start , there was no mechanics of enemies carrying mana crystal, but then I figured out there is no way for player to get stronger while enemies keep sending stronger and stronger units. Mana crystals was the quick solution, which worked super well in the end.