Hey, this was a fun game! First thing I'd like to mention is that I didn't read the game's webpage or controls menu before starting. The game should teach you how to play as you play. I was able to figure it out since the controls are really simple. But, I do wish there was a tutorial that I could play through instead of reading to understand how to play.
I think the shooting gameplay is fun. However, the number of enemies was way too much for me. Going from 30-ish enemies that could be cleared in less than a minute in wave 1 to 132 enemies that I didn't clear and lost to after 2-4 minutes was a bit much for me for only the second wave.
I wasn't sure if I was ever actually hitting or damaging enemies or not. There's no in-game communication telling me I hurt enemies until they disappear. This can be done by making them flash red when they're hit, play a sound effect, etc. Just give something to make it clear that the enemies were hit. This wouldn't matter if they all died from one hit. But, if that's not what you want, I think it's important to give that feedback so people know that damage happened.
In regard to polish, if you wanted to put sound effects in, giving the gun a sound effect would have been really cool to make it feel more powerful.
Occasionally, there were parts of the environment that would slightly block my view of enemies since the environment was higher than them in the world. It wasn't a huge issue for me, it only happened a few times. This is a small nitpick, but I didn't really understand how the game fit the theme of "joined together".
Overall, I think the actual gameplay and shooting the enemies with the gun is fun. But, I think I need more indication as to when I'm hitting enemies and a basic tutorial so I know how to play without reading a controls menu or the game's webpage. Great job on this game, I think with some polish it could be even more fun!