Like many Unity WebGL games on Itch, playing this "locally" via the Itch app requires un-gzipping the *.gz files and editing the index.html to point to the un-gzipped files. The technical reason for this is that the Itch app nstalls the files and "serves" them locally instead of serving them through a web server, and therefore, there are no web server headers to indicate gzipped binary files.