This was a very cute experience, and quite ambitious of a scope. This made me like Renko a lot, and hopefully that's a good way of expressing how much I enjoyed it~
I know you all don't need me to mention the bugs, so I won't lol except for one in particular. What ended up happening, I think, is that I during the Flandre game, the challenge ended on the same frame, or maybe just within a certain amount of frames, as Flandre touched me. I did briefly see the cleared message, but this caused the game to freeze on the loading screen. I thus assumed I hadn't cleared it since it hadn't felt like I did anything, it just ended suddenly and I never reloaded back into the room with Remilia.
Internally, however, the game still treated the challenge as being completed, which I didn't know due to how saving works. It just records whether the challenge has been completed without saving the state of the room when it's completed, so as far as I knew I still hadn't completed the challenge.
As it turns out, the Flandre challenge will not end if you try it again when the game thinks you have completed it. Or, at the very least, I had somehow entered a state where that was the case. You can make ever Flandre pshing into point items and it will still never end. I spent a very long time being stuck at this point, and restarting the game multiple times after beating all the Flandres and waiting while nothing happened, until I looked up a video of someone else playing it. At that point I put two and two together and realized I must've completed it at some point, and sure enough I was able to go to the last room after restarting again.
To jump off of this, what this extended play time brought to my attention was the controls. It was uncomfortable from the beginning, but, as someone who deals hand/finger pains repetitive key presses and holding keys down, playing for an extended period of time caused it to get close to pain territory. Particularly the combination of running while constantly moving, which was the whole purpose of the Flandre challenge. This would be pretty easily remedied with controller support, I feel, since this wouldn't happen if moving was mapped to a stick while, say, running was mapped to a trigger. I imagine controller support had to have been considered, but wasn't added for whatever reason. Time or maybe the lead developer doesn't have a controller themselves to test it with, stuff happens.
I'm not holding it against the game very much, though. It was a bug and partly my own fault as well that I ended up playing for so long, and the game wasn't intended to be played for that long, so no worries. I just wanted to use that anecdote to highlight the importance of controls and supporting multiple options. Sometimes it's not just a matter of convenience, but accessibility as well.
Given all of that, I want to be clear and emphasize that I still thought this was a wonderful, charming experience. The aesthetic was very cute and unique, the music was very calming and also mysterious, which fit the tone wonderfully. The writing was charming and felt very Touhou. Being the huge Sanae fan that I am, her making me laugh at the very beginning gave a very good impression, and the ending concluded it on a very heartwarming note~
In terms of the puzzles/challenges themselves, they were neat but kind of a mixed bag. Youmu's room was a straightforward platforming challenge, which in hindsight feels kind of strange given how little focus platforming has in the rest of the game. Byakuren's riddle was cute, I gave her the origami hat. I'm guessing the iron dome thing was also a solution? Though when I tried it on another run it didn't work, though maybe that was an issue with the save system somehow since I had already cleared the room. She didn't react when I brought it to her.
Aya's room was weird. I had gotten stuck here. I'm not sure if presenting a picture of the fish on the wall in any way can be a solution, but eventually I did go and take a picture of Youmu since Aya mentioned her when talking to her again. I hadn't tried this since I kind of assumed it was more of a joke than a hint. I'm not sure if there's actually a solution that involves the room Aya's in and something she says initially before talking to her again. If there isn't, then I think it's strange to basically require the player to talk to Aya again to know what the solution is.
Remilia's room, despite what I ended up doing to myself, was very funny. Suddenly being chased down by multiple Flandre's got a good laugh out of me, and I thought the puzzle was good as well! Though, I'm not sure what the actual clear requirements are. It doesn't seem like you need to actually make Flandre clone disappear? I think that might've made for a more obvious goal once you realize what happens when you take pictures of them, rather than the challenge seemingly just ending suddenly.
All in all, despite my criticisms, I think this was very good and had a very unique, charming atmosphere. Great job to all of you!