Cute game! I really enjoyed the progression in player ability as the game increased in difficulty. I think my favorite part was when the helicopters showed up and I had to scramble to get my cooldowns aligned to beat them.
That being said, I felt like the game was a bit too easy due to how dropping boulders and other effects on airborne enemies conveniently handles the grounded enemies as well. I would've liked to see an armored grounded enemy - something like a tank that could take a lot of damage, requiring you to divert your attention toward it and away from the many other stresses around you. Also, I did not realize until after I read the submission description that you could use the snowmen to launch snowballs, I did not feel like their inclusion was as meaningful as the cooldown abilities.
Regardless, I had a good time with your game - good job!