Man this game improved a lot since I last played it. Gameplay wise it's a lot more fun. I'll go over the stuff that I really like first, then we'll move on to some of the stuff that still needs some improvements.
1. I really like how it's a mix of space shooter + bullet hell, but with a points system instead.
2. The boss is challenging but not frustrating. Damaging her is a lot more intuitive, more logical. I'd say right now the boss is just about perfect.
3. I like how the game changes during the boss fight and that change goes through in the levels that come after. It's pretty clever and I wonder if it's fully intentional.
Lemme explain in detail. Before Trixie, the game gets progessively harder, but the focus is still mostly on shooting parasprites, not avoiding them. As you go on, you keep trying to shoot them even though the best option would be to avoid.
But the boss fight actually tells you: "sorry, no shooting, just avoid stuff - that's what matters!".
So everything up until the boss fight is like a tutorial level, a chance to try out the controls and get used to the flight pattern. After you passed Trixie, then the real game starts and you're prepared to avoid and shoot.
It puts the gamer in a different state of mind in a pretty clever way, conditioning them to focus on avoiding.
Now to move on to some things that I didn't like. There's two game design issues here and a couple of graphical and sound design issues.
1. I have no idea what my score is or what's adding score. Again, play Robot Unicorn Attack to see what I mean. Everytime you grab a fairy or dash into a star, you can see the amount of points you get. This goes all the way back to the NES days: hit a goomba, that's 100 points.
In a game where score matters, I'd like to know what my score is while playing. But looking means I have to take my eyes off the enemy, which I don't want. Robot Unicorn Attack has a grand solution: every 5000 points you get, a dolphin appears.
This is a small visual cue to tell the player: you just reached a certain milestone. That'd be great to do either for a certain amount of points or whenever you get to a new level.
Also the score is at the top center in RUA, as opposed to the right bottom corner in your game.
That brings me to the second point.
2. The HUD's confusing. The rainbow bar is in the middle bottom, so it makes me think that's the most important part. But isn't the health bar supposed to be the most important in a game where survival matters the most? For a while I actually thought the rainbow bar was my health bar.
Same thing with the score and level. Score matters in this game, after all. It'd be less of an issue if there were other visual cues to tell me what my score is, or what level I'm on.
It'd be an easy fix though. Move the health bar to the middle and make the score number and level number more obvious: now it's just black letters, boooring!
The HUD being on the bottom isn't that big of a deal, but you should know that most games have them at the top. Personally I think for a space shooter you'd rather have it on the bottom so I totally agree with that decision.
3. The power-ups
I have no idea what they do, which in the beginning would be fine.... If I knew when I could use them. I just tried out the game a second time and I think you need full rainbow bar for the "overdose" one and only a little bit for what I think is slowing down time? I was using Fluttershy at the time, I dunno if the characters have different special moves or not.
The overdose one is pretty clear after you've used it, but it's a complete waste if you use it before Trixie. A tip would be to 'unlock' the overdose, in the same way that you unlock Fluttershy. Alternatively, she can just tell you what it is.
Personally I'd seperate the power-ups from the Rainbow bar. You've obviously played Star Fox 64, so you know that the bombs are seperate items. You start with two, but you can gain more by shooting enemies.
Oh and the time slow really needs a visual cue. The overdose is pretty obvious, but one for the time slow would be nice.
And that brings us to the last issue.
4. Sound effects and music.
This is the biggest issue with the game by far, it's really gonna need some sound effects and music. I know it's not done yet, but it should be the next step.
Look at Super R-Type that I linked earlier, and Star Fox too. Super R-Type has a lot of really subtle sound effects with the shooting, charging, explosions, on their own they'd be boring and too soft. But since you're constantly shooting and there's constantly stuff exploding, they meld together really well.
And well, that's that. Hope this helps you out.