Thank you for the kind words, really made my day. Particularly glad that you picked up on what I was trying to achieve thematically / plot-wise with the death / rebirth being in a similar but different world. It wasn't just me duplicating the Scene and chopping bits out... OK, it was a bit, but that's lame so I made sure what I kept was interesting - plus it hopefully aided the player a bit re: environment familiarity. Right, this is a long reply, hope you'll bear with me...
I didn't have time to implement real-time plot exposition (those start of level messages were something I literally added during the last hours). So in the end I left it to the player's imagination, which you have definitely taken and run with. Again, as I commented on your game - you pulled it off very well indeed.
The theme I have in my mind was the player was killed in a space battle, and those (invincible) boss encounters are fragments of that last battle, each 'death' strengthening their link to their soul, the changes to the level reflecting increased memories of what happened... Until eventually they have the strength to finally defeat their daemons and be laid to rest / join the singularity / put down that oh-so-lickable hypnotoad. But I definitely would want to make that a path of realisation. You can probably tell I'm struggling to articulate it ;) This is definitely an area I want to focus on next in general as I LOVE games with an immersive storyline. So long as they don't get in the way of the core gameplay.
On the bugs / issues: yeah things chugged a lot at the end on WebGL. For the next jam / iteration of the game I'll get object pooling in. Game has way too much real time GameObject instantiation going on. It's pretty rockin' on desktop though, but I definitely had to stop at the 5 bullet spread on the main gun.
The shooting whilst dead... I left that in deliberately / lazily as a nod to the theme (note the enemies don't shoot after they die - as that would be [was] super annoying) but I agree it's rather glitchy and a bit lame, so I'd better ditch it or have a better indication that it's intentional.
Boss not being tough enough: yeah, agreed - 1000hp seemed like a lot but with L4 upgrades you're basically a mobile death star. Tweaks I made to the player ship speed probably made it too sluggish to track the player too.
Again thank you so much for the review, after the first weekend I basically had the physics, gunplay, most of the tiles, explosions and particles in, but not much of a game (or particularly an idea). I poured everything I had into this over the 3 days before submission time. Kinda broke me for a few days after ;)
With a bit of luck this Game Jam and wonderful feedback / motivation from people like yourself will finally give me a kick up the arse to follow my dream proper and release something of a commercial grade. Cheers!