This one isn’t super well known, but for small projects I really like raylib, and raygui. It gets impractical for complex GUIs, but it does make it really easy to quickly start something from scratch.

It isn’t the first time someone built a heavily trapped, walled and patrolled border of that size.

Take a look at the Inner German Border. It was over 1300 km (approx. 810 mi) long, and was (average) about 5.5 km wide (a bit more than 3 miles).

From 1974 to 1979, 4956 people attempted to cross it, and only 229 (4.6%) actually made it.