Hey, fun game! First things first, I'm not a fan of text based tutorials. I hate reading, but I love playing. So I recommend letting players experience the tutorial rather than reading it.
Also, I'm not sure if it's just my computer or not, but I tried playing the game in a browser and it froze each time. Sometimes before the level started, sometimes while fighting enemies. Not sure if that's just my machine or the game itself.
I really liked the speed of my projectile. It made it feel good to hit enemies. I also like that you give visual feedback that enemies are hit with a small knockback, good job on that. I think I also would've liked a small flash of red on the enemies or some other visual indicator in addition to the knockback to make it just a little more obvious. I found it got a little hard to see who got knocked back when the tanks were in a crowd sometimes.
I also really liked the death animation and the sense of permanence between levels since the dead tanks stay where you killed them. The particle effects around that were also really cool.
That being said, I didn't care too much for the speed of the enemy tanks' projectiles. They were so fast that I couldn't really dodge them very easily. It made it too hard and my health was too low to do anything meaningful with it. I never made it past wave 2, I think in large part due to this. So, turning the projectile speed down for enemies I think would help make it a little easier.
One final nitpick, I'm not sure how this fits the theme of "join together". But, I had fun, so it doesn't matter too much for me.
Overall, I think you have a fun game here, it just needs a little more feedback and polish for the sake of gamefeel. Good job!