To let you all know, kiss_sdl is now at https://github.com/actsl/kiss_sdl2 .
GitHub even refused to delete the entire repository, so that the old URL were available to me to upload my repository to the same URL again, in spite requested. After some person submitted a DMCA notice, because of asking help in building for Android, and after receiving help, requesting to delete the issue attachment file with the build of some files of unknown origin referred to somewhere in the Internet, that i cannot delete myself, and GitHub refused to delete that file. This is too much nonsense all at once, certainly it caused disruption. So you now know that the project it is at the new URL. I'm really sorry for the trouble it undoubtedly caused to all users, including to these 64 good people who gave a star to kiss_sdl in GitHub, trying to do all they can to promote the toolkit. Many thanks to all users of kiss_sdl, and sorry for inconvenience again.
The old thread of kiss_sdl is at https://discourse.libsdl.org/t/kiss-sdl-simple-universal-gui-widget-toolkit-for-sdl/21675/108
kiss_sdl -- Simple generic GUI widget toolkit for SDL2 https://github.com/actsl/kiss_sdl
The following is an example of using the widget toolkit in a game, this is a screenshot of the project https://github.com/solarHunter/solarHunter by the permit of its author.
Notice that GUI has to be simple, to not interfere with the advanced background.