Loved it! From a technical stand point, excellent implementation of AxRom, great clean graphics that make it clear what's going on generally.
I have lots of nitpicks with it - feel free to ignore all of these, as they are purely my thoughts and opinions:
I had a tough time controlling it - I think we spoke on the discord, and if you are going to map a or b to accelerate, it will make it a lot easier to control. Once I did this in Mesen I could really get in to the control. It was still tricky but it felt less like I was fighting a control scheme.
I felt the difficulty ramped up to an extremely high level - I'm not sure if this was on purpose, but there were two missions I just couldn't beat quite far in and I had to figure out how to freeze some memory values to stop the timer and health depletion to get further in the game. I still haven't quite completed it. I feel like some of the later stages could use a longer timer, especially those in which you are encouraged to move slowly, as it would be a nice mix-up of the formula for that to be more relaxed in terms of a timer.
The other mission I couldn't complete without a cheat just seemed to have an insane difficulty, even when my particular ship was maxed out, but this could just be me not being very good at the game! To avoid any spoilers, this was the red level.
The game also crashed on me quite a few times before I was freezing memory. I've saved some savestates of when it happened if you wanted them, let me know.
I found the movement patterns and constant respawning of the bots (the triangle like enemies moving in cardinal directions) a little unfair and not particularly fun - I don't see a good strategy for defeating them or avoiding them given how quickly they move and respawn.
Finally, there seems to be a min-maxing issue with the ships - one of them seems to be much more useful then the others, and one is not very useful later in the game. They also cap quite quickly, which is useful in a way as you reset them to level 1 on destruction, but also means they never get particularly powerful. Some more pronounced variation between them and possibly more of a ramp up in terms of power acquired might be good, with less resetting of power levels possibly.
I thought this was great and really enjoyed it, thanks for making it!