FYI, ammo doesn't work yet (and lots of other stuff is unfinished)
WSAD / Arrow keys / Right Click to move
Left Click on items or hold Space / E to pick stuff up
Left Click the items in the inventory to rearrange them
Left Click somewhere on the ground to drop the current item there from your mouse
Left Click anywhere else to fire your weapons
Right Click items in your inventory to use them (med kits, for example)
U to show / hide the UI
F to toggle fullscreen
I made all of the art and code myself; use whatever you want