Slugcats go brrrrrrr...

youtube-rainworld.css

/* ==UserStyle==
@name           YouTube RainWorld
@namespace      youtube.com
@version        1.0.0
@description    RainWorld themed YouTube experience
@author         farisfaikar
==/UserStyle== */

@-moz-document domain("youtube.com") {
  #logo-icon
  {
    content: url("https://media.tenor.com/ehVSvi4yzCwAAAAi/rainworld-driving.gif") !important;
    width: 120px;
    height: 35px;
    object-fit: cover;
  }
  
  ytd-topbar-logo-renderer
  {
    width: 0%;
  }
  
  ytd-yoodle-renderer
  {
    content: url("https://media.tenor.com/ehVSvi4yzCwAAAAi/rainworld-driving.gif") !important;
    width: 120px;
    height: 35px;
    object-fit: cover;
  }
  
  .ytp-scrubber-pull-indicator 
  {
    background-color: #fff0 !important;
    height: 60px !important;
    width: 45px !important;
    background-image: url(https://i.imgur.com/TAqcxC2.gif) !important;
    background-repeat: no-repeat !important;
    background-position: center !important;
    background-size: 43px, 80px !important;
    bottom: 15px !important;
    left: -28px !important;
    transform: scale(1.2, 1.2) !important;
  }
  
  .ytp-swatch-background-color 
  {
    background: #ffffff !important;
  }
  
  .html5-play-progress, .ytp-play-progress
  {
    background: #ffffff !important;
  }
}