First off: the presentation is great. It all looks somewhat professional, and it's really pretty. The technical aspect is great, too - the menus work well, player selection is good, and the programming itself seems very well-done.
However, the actual danmaku design needs a LOT of work. The stage is just streaming with a single instance of dodging unfairly fast rings, and that's it. Play some actual Touhou stages, note what makes them interesting and fun, and make your own. There was a post about stage design somewhere (the PoSR thread maybe?), so ask around for that if you're interested.
In addition, Aya wasn't that interesting of a boss fight (although, like I said, the presentation and graphics are great). All her attacks suffered the same problems - it's either basic dodging with no uniqueness (as in her first nonspell) or gimmicky ones that will kill everyone that plays them unless they know what's coming, like the fast tengu bullets from the side. Her last attack, where the challenge is outsmarting the camera, is pretty much impossible until you've died once or twice to know what's going on. However, though gimmicky, those two attacks looked pretty fun and well-designed, just not suited for a full game. Imagine playing a 30-minute game, then failing on the last boss because you didn't memorize the pattern beforehand! Remember, your players don't know how any given attack works until they see it first.
As a suggestion, I think you would be better off making a StB/DS-style "spell card compilation" rather than a full sequential game, with everything just selected from a menu like in spell practice. Gimmicky attacks (which seem to be your specialty) are much more well-suited for that, since dying has no penalty at all and restarting is quick. The player can take as long as they want to figure out a card and they're not penalized for it since restarting only takes a few seconds, therefore attacks like Aya's spell cards in that video become much more fair and fun! If you released a series of spell cards like that, I'd certainly play it, but I'd be a lot more reluctant if it was a full 6-stage game and I had to go through boring stages and memorize things as I go.
Summary: stage needs work; nonspells are generic; spell cards are fun but not well-suited for a continuous game; make a series of single spell cards instead.
