On push the github action described in .github/workflows/pages.yml will compile the code with svelte on nodejs. Then the output the compiled code to "gh-pages" branch which is github pages default load source for https://flmath.github.io/.
The main page picture based on: https://www.pexels.com/photo/city-view-photography-2129886/
In the dark mode: https://pixabay.com/photos/castle-hohenzollern-night-fortress-811336/
The different geometrical figures based on:
the Penrose triangle https://en.wikipedia.org/wiki/Penrose_triangle
Oscar Reutersward "Blue Meander" http://www.zludzenia.pl/reutersvard,5,5,oscar-reutersward-bryla-4.html#showimage
M.C. Escher https://en.wikipedia.org/wiki/Impossible_cube
Sun and Moon https://pixabay.com/vectors/sun-moon-anthropomorphic-heavens-8015960/
Most of CSS: https://www.makeuseof.com/css-background-patterns-examples/
CSS animations: https://www.youtube.com/watch?v=q-i0rZBZvBk
PWA: Based on: https://dev.to/100lvlmaster/create-a-pwa-with-sveltekit-svelte-a36
The rest of resources, links to them and their authors are in devnotes.org and RESOURCES.md.