It's a messy code but I had no problems with any lag.

A dark theme that won't hurt your eyes.

(IMPORTANT) To make this design work:

1. Go to Settings

2. Change "Background" to "Lights out"

3. (Optional) Change "Font Size" to smallest.

For themes I recommend Stylus, I do NOT recommend Stylish, they are a data collecting company! https://add0n.com/stylus.html