I just released a new version. It’s now called Sideshow, mostly because I ran into trouble making the existing version update in Simplify. So this is technically Sidecar 3.0. It adds one major change: adaptive sizing. Previously I’d needed to have a version for a 13” display and another for a 15” retina display, but I figured out how to have adapt itself based on the current screen size (I think, let me know if you find otherwise). The width of the player, font sizes, etc. will all adjust to provide a fairly uniform experience across display sizes and types.
It also measures and updates the length of the text for the artist and title displays, adapting the placements to show as much of possible of both.
When hovering over the jacket, controls appear for previous track, play/pause, and next track. You can still Command-click anywhere along the progress meter to set the play position. Clicking anywhere on the jacket will still toggle play/pause, and shift-click skips to the next track (because double click stopped working).
Check it out on the project page, or just download below.