This is a fun and at times incredibly frustrating game. It's part of the nature of upgrade shooters you have to die in order to really have those upgrades stack properly. As you defeat more bad guys, you get better upgrades, faster elf minions frost, fire and poison damage and more. But as you progress so do your enemies and you will find yourself pitted against more than one foe at a time scrambling to both avoid the red bubbles of your foes, as well as their dark friends.
If you can survive through 15 waves of evil Christmas will be saved. If you can't, well, you get to keep your upgrades and try again.
You can play for free at www.kongregate.com.