That's really cool that you're developing your own engine. I'm sure it wouldnt be trivial but a custom skybox + some distant fog to blend the horizon would make this look so cool. The mirage effect here was absolutely evil and fits the theme of the jam excelently. Nice job!
btw would love to play in fullscreen! I tried making the window bigger but then the game wouldn't recapture the mouse so I had to relaunch and play on the small window (very small on 4k monitor)