YTDJ! is a kind of joke. I've frequently seen people trying to make their best transition bewteen two tracks played as Youtube videos at a 192kbps AAC quality, quickly switching from a tab to another to lower the volume of the last track and make the next one kick in in a fancy manner. This problem was already addressed more than 10 years ago with the unforgettable twoyoutubevideosandamotherfuckingcrossfader.com, but it was kinda erratic to use and quickly stoped working, as Youtube's API was updated. So I decided to revive this classic, and YTDJ! was born.
In the first version, the backgound was procedurally generated and animated using P5JS but I ended up exporting the static result as a SVG, and animating some shooting stars with plain JS and CSS.