It's good enough as a jam game.
Gannio already commented on the gameplay and balance, so I'll drop a thought about the music instead.
The composition is not amazing but not bad neither. The ZUN style is budding...
I have no music composition nor actual music theory experience (just that I have experienced the soundtrack by playing the Touhou games over the years) but:
Consider using other instruments for the main melody for variation. ZUNpets are great for emotional and/or strong song segments, but overused or misused they're overpowering - which I feel is the case for your song.
Try also having a secondary instrument accompaniment that supports the ZUNpet main melody with a similar intensity, to balance out that overpower.
The chord progression also feels like the ZUNpet is always in a chorus/climax state, without lowering its intensity to a lower energy state. That stagnation in this climax state makes it seem like the ZUNpet is perpetually screaming rather than singing a song's strong, memorable point.
I can still advise you to maybe use several of ZUN's songs as case study.
More in particular I'm thinking of:
- "The Gensokyo the Gods Loved": The ZUNpet is used for verse, bridge, and chorus, so it's effectively more like a singing voice. A good song to study basic song progression for a single instrument.
- "Emotional Skyscraper ~ Cosmic Mind": The song starts strong with the ZUNpet but only for the explosive intro. It's follwed by a rather calm verse. Then the ZUNpet comes in again, it's the same as the intro but it's soon turned as a build up that grows in intensity and then becomes the chorus. Then at last the ZUNpet lets go with a resolution. The main thing here is that the ZUNpet "has its moments", it comes suddenly for impact, and it "says a temporary goodbye" for its next strong return.
- "Unlocated Hell": The song has 3 main instruments that take turns. It starts with the electric guitar and the piano, which play off eachother, -with call-and-response, then duet then countermelody. In the second third of the song, the song's structure is the same but the piano's taking a break, the ZUNpet's here instead!
The main takeaway in this case is how the 2 main instruments are completing and sometimes competing with eachother, as to balance eachother out.
Now, of course I'm not asking you to be the next ZUN, but to me it seemed like this original composition of yours is important so I think in-depth feedback on it is relevant. Besides, I already like how you already kinda got the composing style's basics down.