Cover, rapid-fire snowballs, 10 waves. That's all I need for 5 fun minutes.
It's fun, but it feels like speccing almost entirely in attack speed is the only way to play. Otherwise you can't really deal with the big hordes at the end of waves.
And with the attack speed boosted, there aren't many twists nor difficulties in the end. In that regard it's a good thing the game's not endless actually.