brainfuck.asm is written in x86 64bit assembly with 64bit wide cells. I will probably make another version with 8bit cells and proper overflow handling in the future, since some brainfuck programs rely on that (don't count on it though, as this is a purely educational and recreational project). I also wrote a C version that is as close to the assembly version as I could make it at the moment, which is what explains some of the rather unconventional design choices.