Hey Ted, awesome little game!
I was playing on mac and didn't hear any sounds, I've heard thats a HTML5 issue. I like the concept, I think you need to make it more clear that the bomb pick up re loads you ammo, even after reading the tutorial I was confused by that. Maybe the first time I use all my bullets you can pause and point to a pick up, More ammo here!
Are there any different types on enemies? don't think I lived long enough to see any.