Well, its playing fine the game but something I don't like is that headshot don't do a critical hit. The enemy's AI need more work, all enemies are very dumb specially in how they react to the player, for example when I fight the mecha I just run around it while I was punched it to death.
Speaking of melee combat, I feel the damage inconsistent, sometimes I one hit a soldier an other time he need 3 hits to die. I think the speed of the character is affecting the damage, most of the time when I run and punch a soldier, he dies from one hit, I'm no sure if this is intended. Also, I don't think there's need for melees combat be separate from weapons, it should have it's own button, for example, in a WASD setup it can be the F.
The graphics are fine because it have a retro fell of a 2000 game, that say the rock part in the first level feel too dark for me, maybe lighten it up a little bit.
The game have potential but need more polish, maybe check out Far Cry Blood Dragon, I think it can give you a nice inspiration if still hasn't played yet.
I also liked the MC, so I made a little drawing of her. Looking forward to see your progress in the future.