I liked overall aesthetics of the game.
Shooting is fun, exploding mech effect and fire on it is cool, backgrounds are nice and atmospherics, locations are clearly distinguishable. Effect of acquiring powerup is nice.
I played through to the fly boss and didn't find where to go further.
The game lacks music and sounds, they can boost atmosphere even more.
A small irritating bug I've noticed: character stucks on some edges where it seems unnecessary to jump, on screenshot I'm pressing right arrow button but not moving
Camera motion feels very jumpy. I can be shot from another screen or need to jump to nowhere because camera doesn't move. It's ok to keep camera still on each location but then location transitions should be rethought in some places. Also, it is unclear where is a chasm and where it is a safe fall. But it's forgiving because it doesn't take too much health.
Movement is a bit too fast to my taste, jumps feel a bit off, but it can be just me, so doesn't matter much. Moreover I get used to it fast, because platforming is easy here.
Text is a bit fast to disappear as for me, but I'm not native speaker, so I had to pass the place triggering text twice to fully read it.
It's sad to lost acquired abilities after death. I didn't notice checkpoints at first, but after first death recalled description on the game page where you explain checkpoints and after that looked for them more carefully. It would be greate to make checkpoints more obvious.
I also noticed invisible walls, kinda makes you fall of the game flow.
In general, I liked the idea and implementation, it just not finished, but very fun to play!