Love your art, sound and level design, i just have one problem though: the health packs.
Now, in about 40 minutes of play, I've only encountered 2. And I'm not sure if you find that a problem or not, It just made me a little frustrated when i died because i couldn't heal myself. Now of course other games don't have healing items, but they make they're levels shorter. If you want to keep it as rare as it is, id suggest giving it more heal, about 3 hearts.
Another thing that I, personally, would like is directional grenade shots.
This is just my opinion. Love your game, keep up the good work