I played as ice first and I kept thinking there was just no way to win, but I eventually figured out that using the lvl 5 special attack with a combination of the top two tiered units would eventually push fire back. I think its Kosheek (sp?) was the reason I was able to damage the enemy tower. The lvl 5 unit could only do melee damage and so it was having a hard time actually getting to fires tower but it could push far enough that Kosheek(sp?) could throw some snow attacks onto their tower while also damaging their units.
It had me going at first. I would also agree that towards the end you are spamming attacks but its a classic of who can click faster and use their special attacks in the right moment.
I had fun so its definitely a decent game. Also that music is great and suits the game play.
Great work on this one!