Quite a nice game, has an arcade feeling to it.
First time playing it and reading that I had to collect ammo made me think that I had to save my ammo and tried to shoot less, but as I played on I realized I had unlimited ammo so I started unloading. A suggestion would be to make the unlimited ammo clear, or change the goal to collect something like medical/food packs.
The sounds are great and the player movement feels good. Well done! and in just 2 days amazing :)