Super fun, a little short though.
HOW TO BEAT SANTA: Collect just 3 emps, and go to the bottom of map, right underneath Santa, and go fast upwards using gas, and then use your emps to jump as high as you can, and try to hit him with you mouth. SNOWBALLS DO NO EFFECT! Also, after that, he falls to the ground and you have to hit him again, although he is very hard. After you kill him then, he becomes Mecha santa, and I am stuck there, but I think you have to hit him in the mouth again, but it's so hard when he uses his fire walls, so I can't help you there.
Hope this helps!