The game feel really nice to play. The controls are responsive, and I like the long jumps as well. The shooting works really well, and it feel really good when you can hit multiple bats with a single bullet!
I just thought that the it was really frustrating how little ammo I got, and how easy I could die. I could shoot once, maybe kill one or two bats, but then I had to run around to collect another bullet, dodging bats in the meantime. Once I had the bullet, there would be so many bats that it was basically impossible to get the next bullet. At least that felt a bit frustrating to me, but perhaps that is just me :)
Finally I thought it was a bit mean that you could not quite jump up to the higher platform from the bottom of the level. You had to make this long jump all the way from the lower platforms on the side. This made it very hard to dodge the bats as well, and just felt a little annoying to me.
Hopefully I was not too critical! I am truely impressed that you managed to make this in three hours, and I completely understand that you did not have time to do this stuff. It was really nice that you managed a few sound effects, which I think really helped with the game feel. Together with the nice and big bullets I think the main mechanic worked very well, as you said. Great job! :D