The red disk will let you position your paper without exposing it.

I'm here with all the rest. I'm also over 30 years of programming/sysadmin/etc, I don't compile my own operating systems or make cross-compilers anymore but still spend many hours at my keyboard and still more than 40/week. Most of my hobbies don't involve computers ( some have parts that do.. I also am into amateur radio astronomy which needs custom software )

That's part of the draw to film for me, but I also like the "tangible' and physical aspect of it, as well as the manual craft part. I just got back to film after being away >30 years.

have fun!