Pixelknight delivers, as ever.
There is very little you can say against a PIxelknight game, except that I wish there was more now that I've beaten it. A couple of notes, though: I see some other complaints below about the second boss. I had a frustrating time with that one myself. It's unclear even after beating him what causes him to attack toward mid-screen instead of chasing the character across the entire field, but once it happens you can get locked into a loop of fleeing straight into his next spawn point with every pass, which is duly frustrating since he's fast enough there's almost no room to turn around and fire back at him once that begins. The boss feels really out of line with the game's difficulty curve, and was definitely a frustrating point in an otherwise good experience.
Also, while running privoxy your continue function freezes the game just before loading the submit high score function, and if I try to quit then continue from the main menu, it comes up with every button highlighted red and unresponsive. If this were any other game, I would probably refuse to play on principle if it refuses to play with my proxy up. I'll work around it because this is Pixelknight, but it would be much appreciated if I didn't need to do that.