This project is a library to extract and edit act and nut files. It was created for the files in the game Touhou 14.5 ~ Urban Legend in Limbo, and was only tested with files from this game.
Nut files are Squirrel 3.x closure files. It was created by reading the source code of the Squirrel sq_readclosure function, and by rewriting it in my own way. I tried to keep the same class names. My understanding of the format is here.
I don't know what Act files are, but they are everywhere in the game, and they contain nut files. All the knowledge from these files comes from reverse-engineering and guessing. There may be some places where I didn't understand correctly the format, and most class names are guessed.