Alphabet is a rhythm game written in SDL. It can load any Taiko beatmap from the rhythm game osu!. (If you don't have osu!, you can still try an example beatmap included in the release; just enter "ex" after you run the game.)
ARForest - Altros [Futsuu] by Eyenine
When running Alphabet.exe, if you get an error about MSVCP140.dll or VCRUNTIME140.dll, make sure you have both the x86 and x64 versions of Microsoft Visual C++ Redistributable for Visual Studio 2015, 2017 and 2019 installed.
If Windows Defender SmartScreen appears, click "More info" and "Run anyway". (I know this doesn't look good, and I don't know how to fix this...)
First, make sure your map can be opened and played in osu!. (In other words, make sure the mapset .osz file is extracted.)
Then enter the map path; make sure to get the full name. For example, given an osu! installation in the default path, you could enter:
C:\Users\<Username>\AppData\Local\osu!\Songs\1184727 ARForest - Altros\ARForest - Altros (Eyenine) [Futsuu].osu
A quick way to get the path is to open the beatmap in the osu! editor, and then go to File > Open Song Folder.
This game is difficult compared to the traditional osu! gamemodes. Even if you are experienced in rhythm games, I'd suggest starting at a Futsuu difficulty or below. Scoring an S rank on a Muzukashii difficulty would be very impressive. :)
Source of the included example map: Ray - Nagi [Kantan] by mingmichael