I really like the idea of this game, it has a lot of potential for expanding. But I encountered some problems. First when I disable the tutorial, my character couldn't move anymore, it got stuck for some reason. This also happened with tutorial on, I would click play, pass all that text, and then I couldn't move as well. Second, when I lost and clicked the X button instead of OK, the game just stays frozen and I don't know if I missed it, but there were no pause button so I had to restart the browser tab itself. Also, the rightmost and leftmost enemies were very hard for the plane to hit, even with all max upgrades, they were the reason for all my losses, the plane would just bounce off the wall and not hit the planes when they got too small. (Also this is more my problem than anything but as always, I was pretty unlucky, I often got 4 to 5 back to back downgrades, and since they stay a lot of time on the ground, they would make me lose some upgrades if I didn't want to get them to get to the upgrade)
Other than that, I found the game pretty good, the character was very charming with his voice lines, and the sprites were very good as well. Congrats on the game!