I'm consistently reaching the second stage now, although the crawler from the second part of the first one still takes me some life. The difficulty might be ramping up from there, which is perfectly fine, or maybe I'm not using my shield enough here, either way it's possible that I don't complete the game before the end of the jam so I'll just comment now.
A detail, (playing the downloadable version) sometimes the level 1 does not load properly. I don't know exactly but it seems linked to passing through the pre-screen too fast, like pressing just Enter really fast, not even pressing C or X before, I think it's consistently reproducible although I've not gone deep inside either. One time I could swear the last boss of the first part of the first stage did not appear either, although this happened only once if it really did.
The game is excellent, super fun to play, except for the weak theme integration I only have good things to say about it. It sounds great and looks awesome, with tons of details, reaching the second part of the first stage then the second stage ... wow all these environment as well as what populates it looks so different and so great ! This crawler ! Gameplay feels perfect, I don't think the shield thing adds that much but I kind of like it anyway. Up to where I played the enemy formations and patterns were already good, crawler is great again, and it seems the more you advance the better it gets so what I've not seen is probably even better. The game is extremely polished, that's stunning.
Congratulations !