This style enlarges the “large player” version of YouTube videos. Instead of a fixed width, it tries to expand to almost the entire viewport.
This style only affects the “large player”/“theater mode”, which is the button right next to the “full screen” button.
This style is constantly updated. I update it whenever it gets broken because YouTube changed their code. If you find something wrong/broken, feel free to contact me.
Also available at: https://userstyles.org/styles/100169
A preview of options you can set in your extension