Really fun and challenging shooter, and great use of the theme too, nice twist on the setting. The shooting mechanics and gameplay was really fun and smooth. Especially liked the patterns of the envelopes and linkedin monsters, were difficult to dodge, but you had to learn their movements and then it became easier. I would have liked it if keeping the mouse pressed would shoot, instead of having to click for every bullet, but thats a minor issue, not a big deal. The pizza and soda bottle were also fun little options for weapons to add some variety and had a nice risk/ reward for the player.
The artstyle was nice, i loved the color palette and the different sprites used. One thing maybe could have helped was to make the background elements which were not interactable to have a little less saturation to make the interactable ones more prominent.
There was a nice feel to the shooting, but maybe could be 'juiced up' even more with screen shakes and particles, i think it would add to the fun element. THe integration with the theme was also perfect and very organic.
What could have added more variety was having a differnet 'boss' visually each time one was destroyed. The difficulty definitely ramps up (i reached the 3rd level after attempting a few times and it was definitely harder!) but having it look just a bit differnet would add to the feeling of progressing.
Overall though this was a really fun entry and well polished, great job :)