The geometry for a particular puzzle is defined in a file with the extension ".sym". This is one of the Foldit_file_and_directory_structure#Puzzle_files puzzle files that are downloaded from the Foldit server and reside in the Foldit installation directory. Unlike the other puzzle files, the .sym file does not have a digital signature, and so it appears to be modifiable. As an example, the puzzle Symmetric Design with Filters has a file 0000996730.ir_puzzle.sym, which looks like this: The second line E = 3*VRT0 + 3*(VRT0:VRT1)