I love the blood splatter and death effect, having to shoot using right mouse button and actually aim in a side scroller is a bit of a weird choice but made for a different kind of shooter.
Also great job on making everything yourself, definitely not something everyone can achieve in 2 days.
One tiny problem I had was with UI not scaling properly, for example I couldn't click on Skip button in full screen and when I wasn't in full screen, the skip button and shop button covered the whole screen.
I quite enjoyed it, great job overall!