As of this writing, I have yet to finish the game, but I think I'm pretty far (btw, I like that the continue option implements the block mechanic). Anyway...
Really cool concept The power-up was very creative and very fun to use, especially blasting enemies with high speed bullets. T
he level layout was also straightforward and easily understandable, even when I had to backtrack I had a fairly good idea of where I was going because I had noted the obstacles and power-ups on the initial journey (primarily the two gun upgrades, but also the upgrade that gave me the Line ability).
I also appreciated that you locked the door in the room with the Boost ability, there's no way I would have figured out how to use that if I hadn't been stuck in that room.
Finally, although super situational, the minigun was super satisfying to use.
Some things to consider:
1. I found the movement a bit stiff and felt a little bit unconfident about my own jumping abilities. This led me to approaching a lot of jumps hesitantly rather than at breakneck speed. I don't know if this was your intention or not, but it slowed down the pacing quite a bit.
2. I liked the variety of enemies, their telegraphs, and some of the situations you put me in were pretty cool (like the room with 4 cannons), but at the same time I was often attacked by enemies which were off-screen (particularly the cannons and the rock spitting guys, but I also got nailed by an off-screen bee once too). This is something I struggled with in my game as well, especially on the couple of vertical sections.
3. The screen boundaries felt a bit inconsistent, I could never tell if I was going to go off screen or not by walking a few steps backwards. This cropped up in a few rooms where you spawn in very close to enemies, I'd want to get defensive and end up running back into the previous room even though I felt like I was fully within the bounds of the previous room.
4. Small thing, but I couldn't tell if the shotgun was doing anything or not? The guns having some SFX attached to them would have helped immensely with feedback.
But yeah, overall a super cool concept and I'm hoping that I can go back and finish it later today. The section I'm at is pretty difficult so I had to take a breather, but I know I can pass it. Overall great job!