Config.txt - Swizpig/ZGloom GitHub Wiki

On first play, a file called "config.txt" will be created in the current directory if not already present. This exposes some video options that are not changeable from the ingame menu. Specifically:

;The size of the game render bitmap. Bumping this up may lead to more overflow issues in the renderer. But you can get, say, 16:9 by using 460x256 or something in a larger window
rendersize 460 256

;The size of the actual window/fullscreen res. Guess this should be a multiple of the above for pixel perfect
windowsize 1380 768

;vsync on or off?
vsync 1

;fullscreen on or off?
fullscreen 0

;focal length. Original used 128 for a 320x256 display, bump this up for higher resolution. Rule of thumb: for 90degree fov, = renderwidth/2
focallength 128

;multithreaded renderer (somewhat experimental)
multithread 0

The multithread renderer is a simple "two-threads, each rendering every other column" affair, with a similar split for floor/ceiling.