I really enjoyed the game and made it to Wave 11, where I spent a long while before finally giving up. I really love the enemy ships—the way they enter, the enemy gun variety, the colors. The way you did the laser cannon was awesome. I wasn't expecting to play for so long, but the way the levels start is so satisfying that I enjoyed watching it every time.
Making the enemies the same but varying their placement was also an incredibly effective way of keeping the levels fresh but still consistent across multiple attempts.
I had two major issues with the game: the first was that the game stuttered immensely for me for a few seconds after detonating the weapon. This was a problem in the later stages, because unless I managed to kill all of the enemies at once, I had a good chance of dying without recourse while my screen was frozen.
The other issue I had was that it was hard to know when my weapon would be ready, as glancing at the bar while trying to dodge so many bullets was not really a possibility. This is probably somewhere SFX could have been a really nice addition, though I surprised how little I minded the lack of audio in the game otherwise. I suppose space since space is silent, it matches up well. :)
Nice work overall! Your game might be the longest amount of time I've spent playing a game in the jam :)