My own website has a dark theme if you have @media (prefers-color-scheme: dark), or if JavaScript is enabled, there’s a switcher in the top right hand corner. Note however that I use Triplicate T3 in the dark theme (300/700 for regular/bold), compared with Triplicate T4 in the light theme (400/700). You can fiddle with the @font-face declarations in dev tools (the font change happens in 2019b-dark.css) if you want to try swapping it out. https://chrismorgan.info/blog/rust-fizzbuzz/ has a bit of code, some other articles do as well.