Well to actually explain the game with no spoilers: its a rougelike game where you roam around a stage trying to open chests for items, then power up a teleporter to move to the next level, rinse and repeat till you are at the final boss (or you loop, restarting the run with the same items). The main draw of the game is the constantly rising difficulty: starting off as easy and finishing with "i can see you","im coming for you" and "HAHAHAHAHA", at which point you are basically fucked as enemies deal 2 times your health in damage and you can barely chip them,chests cost as much as bill gates worth and the screen is a clusterfuck of item effects. You have a wide variety of characters, such as:

Guy with 2 guns
girl with homing bow
Spy tf2
A robo plant
demoknight tf2
engieneer tf2
2009 honda civic with a railgun
demoknight tf2: grappling gun edition
POISON PUPPY :3
Dumb stupid dumb dumb space lady

and 2 dlc characters

sniper tf2
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I suggest buying the dlc if you can, it adds more items and, most importantly, GUP

finally, always remember to B U N G U S