This game is almost impossible to beat without cheating! But the boss was fun, even when I was cheating. Because I couldn't shoot when I was hit, it was a fun challenge to bet the boss quickly. It wasn't about if I could do it or not, as I literally couldn't die, it was about how fast I could do it.
I found it annoying how I sometimes just couldn't move vertically and sideways to dodge enemies, but I think I can guess why this is; This is actually a vertically scrolling shooter, like Xevious, where the players movement is limited to a box. However, instead of having the view of the camera imply where the "box" is, the camera is attached to the player and the "box" is invisible. I suppose it's fine to remind everyone why designing the camera to show where the player can move has been a staple for 40 years now :p