Webgl or webgpu, but for ui you can just draw to a canvas and copy that canvas into webgl/webgpu. That means you can easily iterate on the ui system in 2d with mouse input similar to what you’ve been doing in python

But, as an example of similar complexity. I hacked together the first Ui I needed. It was 6 buttons and a slider. Then I realized I needed two more Ui panels and started to write more real Ui classes to abstract stuff out and, it just starts getting more and more complicated.

A slider needs to “capture the pointer”, meaning as you drag it, if to drag past the end of the slider and the pointer is now over another widget the events should still go to the slider. It’s not hard to implement, it’s just frustrating for me that I don’t actually want to write it. I just want to make my panel and if I could just use html id be done. Instead I’m spending my limited free time making this ui system. I don’t have that much and would be much further along in my actual goals except for this road block