According to the interloper wiki, int_menu consists of two parts - a red room and a chessboard. But there is one problem.
not equal
The textures of the floor vary (HD and emo). You don't need a key to get through the door on the INT4 int_menu map. But the lights are very similar.
My theories are:
Either the int_menu map consists of small (red), medium (HD), and large (EMO) planes,
Either the EMO plane is the lower bound of coordinates (because in that version of the engine, coordinates are expressed in hex code with 10 characters per dimension, meaning the infinite world is finite)









