This was really nice! The main thing you did was shooting enemies, but it felt really satisfying each time you hit one. The blood splash, together with the sound effect and the dollar sign that came up. To make it feel even better a (subtle) screenshake would add a lot I think. Walking around also worked smoothly and worked great.
I think the main point of feedback I have is that there is not so many interesting decisions to make during the shooting. Of course there is the shop, but during the gameplay itself it does not really matter what you do. If there was a way to take damage, for example, then there would be risk-reward scenarios. Like, do I continue playing a little bit longer for some extra money, or do I go to the store now and not risk dying? Adding damage is not the only way to get these kind of decisions, but it might be something to think about :D
Anyway, a good and solid submission! You did a great job with the game feel, especially considering this is your first published game! Good luck with all the other games you will make :D