I haven't dug into this engine a ton just yet, but from what I've seen so far it looks amazing! I was JUST using pico 8 thinking "man I wish there were a JavaScript version of this" and here it is! This looks great. I've only been tinkering with it a little today but it looks awesome. It gives a ton of control to the developer while also getting rid of all the annoying boilerplate of setting up a local server, serving image files and textures, setting up your update loop, adding listeners for inputs, etc.
I'm excited to try this out more!