TXT format can only be displayed in the font of your computer. TXT text itself is plain text, and there is no format at all. If you want to learn calligraphy, you must convert the Chinese page of the book into a picture format, which generally supports JPG. You can download some calligraphy in JPG format in your computer (you can directly search for "calligraphy" in Baidu pictures), and then turn it over with software to make the pictures smaller and easier for mobile phones to read.
Or have proprietary calligraphy software in JAR or JAD format, but also embed pictures in JPG format.
The running script of TXT is limited to the pseudo-running script of ASCII code. It actually looks like a bunch of weird symbols, which may not be supported by mobile phones.
I don't know if you understand.
For e-books in calligraphy jar format, you can go to Baidu's website to search for calligraphy jar.
There is also EXE format, which is not supported by some mobile phones.