It's a hard, but fun game.

Although the graphics are simple in comparison to the others, it has a lot of detail, thanks to the story, the bullet patterns and specially the soundtrack.

When playing it for the first time, dying is inevitable. Thankfully, retries are infinite, so it's possible to keep playing to gather skill until reaching the end. There's also a practice mode in case you just want to observe the patterns or watch the ending faster.

I only have a few issues:

• The 45º rotation is a little bit annoying to aim and shoot, and sometimes you can get confused with which button will rotate left/right. This can be observed in the first level, when you're supposed to dodge bullets by moving around counter-clockwise. It would be cool to be able to aim directly with the mouse, or having a smooth rotation instead of the instant 45º switch.
• Cutscenes can't be skipped after retrying. While it doesn't repeat literally everything from the start, it's still a little annoying to spam the skip button until you start over.

The game itself is pretty short, with only 3 bosses and 1 extra boss after the ending. But bullet patterns are pretty diverse and there are a plenty of them, so in order to master each one to defeat every boss can take some time. You can also try playing again for a faster time or for a no-damage run, which could add to replayability.

Very well designed overall!