Multiple, by 
I’m being kind to you because this is your first level. The general idea of your level is ok, but you need to:
-make the level entirely solid down there, so that you can’t fall off.
-make the walls thicker than one tile
-place the enemies in a better way (lab rats??? Skeletons??)
-make the level harder, longer and more challenging (because this was crappy short)
-at least fill in something in the music and next level entries
-remove the weak coop element
-USE the tileset and USE the different layers
-remove the exit sign near the endboss, ‘cause if you shoot it the level will be ended
-make the level more logical; is there anny point to what you’re playing through?
You will probably want to gain some more experience, but this isn’t bad for a first level! Mine was so much worse…
