Game File: 

NightmareSquadInstaller_DoorFix.7z

Made for TheCube for Christmas. Sorry I'm late!
This game isn't particularly Christmas-themed, but that just means you can play it year-round.
Game includes completely original music, sounds, sprites, and backgrounds. Font is Casual Encounter by Anna Antropy.

Long ago, an evil queen attempted to rule the world with a dark cloud. Although she has been long slain, fragments of her powerful magic remain, and have been invading the Dreamscape, a world where minds go when their bodies sleep. Four agents calling themselves the Nightmare Squad have come to put a stop to these abominations!
Game isn't particularly buggy, but I've only finished two levels so far, so it's a little short.
The goal of each level is to find all the keys needed to unlock the boss door, and then to defeat the boss monster. There are several shops in each level as well, and your friendly neighborhood Charles the Giant Carnivorous Plant will be happy to sell you items in exchange for Quartz pieces you find around the level! Various items include Bombs, which you can throw to destroy rocks and heavily damage enemies, Carafes, which will instantly refill your health before you die, and life-extending potions. Each character also has 5 Star Cards hidden around each level. These can be collected by shooting as well as touching them.

Controls:
A and D: Move left and right
W: Jump
Q: Throw bomb (if you have any)
Shift: Attack (you can hold it to constantly fire)
E: Go through doors, activate switches
Esc: Pause/Forfeit level (will prompt you)
(Warning: There are some debug keys that probably either instantly kill you or restart the game still bound, so try not to bang your keyboards much)

Character's attacks:
Sammy: Rapid fire, short range, easy to hit with wave attack that can go through walls.
Crockett: Long range, slower shooting snipe shot that does more damage than Sammy but can be harder to hit with.
Ulix: Small area-of-effect sphere that constantly damages any enemy caught in it.
Izzy: Long range tackle that sends you flying straight forward and does massive damage on a successful hit. Will collide with walls. Izzy can be VERY easy to die as, so be warned.

Attack types (Changes based on the kind of element card you collect)
Fire: Higher damage than normal attacks, as well as an added burst effect that harms nearby enemies as well.
Water: Lower damage, but goes through enemies and can push certain ones.
Electric: High damage and goes through enemies. Can also activate generators, toggling generator blocks (marked with a lightning bolt) on and off.
Ice: Buggy. Does higher damage than normal and will turn enemy into an ice cube if their health is low enough, allowing for a faster kill and a platform. Can get you temporarily stuck some times, though, so watch out!

Some enemy behavior can be buggy as well (especially Dojies, who will charge at you if they spot you).
The game will save and load high score data (tracks cards collected for each character, highest quartz at end of level, and levels unlocked), but I'm not entirely sure if it created a fresh file, so don't be surprised if any levels are already unlocked or there's high scores already there.
Use mouse in menus and in the store.

If there are any other questions, please ask! I'm still working on the game and plan on adding tons more levels and things.