This already feels very polished, with good enemy and weapons variety, fitting sound effects, and a nice retro pre-rendered 3D sprites aesthetic, great job! The level design was also really well done, keycard based progression felt right for this style of game and made the maps flow well. The levels also felt distinct from each other and made sense internally. Add some music to this, and this game could hold its own against some retro shooters!
My only complaint would be that mouse acceleration seemed to be activated? I usually prefer no acceleration for more accurate snap aiming. Maybe it was just my browser though ;)