Hello. I got Marathon & Marathon 2 on a 2nd hand computer and started playing. I liked it. I use an old laptop with Windows XP. The map function causes an immediate exit to the desktop so I don't use it. It makes the game more difficult and I developed a style of play of going everywhere I could get to and touching everything I could touch. I played most of Marathon on MD but changed to TC on Marathon 2 and Infinity and have used this level ever since on Tempus Irae, Rubicon, Eternal, etc. all of which I am in the early stages i.e. five or less levels. I am not able to get through 1 Bigger Guns Nearby on TC though I'm still trying. Perhaps I'm hindered by my scorched earth policy type of play. I use TC to make the game last 'cause if'n you can finish a game in a day or week or month it's too short. After finishing a level I'll look at the spoiler or now the Tour of Duty (really great stuff) and if'n I missed something, I'll go back and go for it. But I cannot wall climb in the depravation chamber. I like Marathon Arena (level 31), it is great for training, expecially running punch. But I gave it a new soundtrack. Durandal Invidia is good training too.
I know nothing about programming. I think a map is the entire game, consists of polygons, and textures which I think are the designs such as brick, stone, wood walls, etc, shapes which are probably shapes of things to come, physics is how big or durable the shapes are, etc. I think it's frightfully complicated. PC's are magic. When I worked I programmed an IBM Sys36 then AS400 but PC's never so I know about programming but nothing like these games (and knowledge now mostly forgotten).
I registered to help with a question in the Projects section and I'm afraid I wasn't much help but you never know what'll give someone a eureka moment. About that, I scratch started Eternal 25 S'pht Happens in both 1.0.3 and 1.1.04b and did like the colors and music on 1.0.3 better.
I hope this wasn't too long. TMI, tl;dr, yawn, etc.