Originally introduced in the Unity port of Doom, later included in the KEX port, this featured has since been introduced in source ports outside of the official releases.
Namely, after my favorite source port, Woof!, had introduced support for the feature, I decided to start this project to give focus to, and highlight, this feature to the wider Classic Doom community.
Check the official Doomworld Forums thread for this project.
Credits to the original set of icons goes to Julia Nechaevskaya.
Thanks to Djoga for improving my first edit, becoming the basis for most other edits of mine.
Melodic Spaceship, for making the Chex Quest icons.