I might very well be trying to reverse-engineer the wheel (since everyone else seems to know how things work, while I'm starting from scratch), but I just wanted to say I'm currently investigating sapper's TR42PRJ tool code because I want to learn the TR file format so that maybe I can convert TR2/3 levels to PRJ one day
Currently I'm trying to wrap my head around FloorData, because I lack much knowledge and fluency in binary and hexadecimal systems, so it all appear cyphered to me. But because it's so fascinating I can't help trying to figure it all out! It's too addictive!