This jam, we wanted to make a game that would work in the browser. LD is about invention and exprimentation, so we made our own engine. It's designed for 2D, and it has good support for shaders (necessary for those sweet graphical effects). It's based on instanced rendering, so the performance is pretty good. It has a nice sprite class, data loaders, render passes, 32-bit floating point math, and even an audio system. I can definitely say it was a lot of work. Hopefully, it will also be helpful. :)

Demo app: https://atomotron.github.io/ld47-prep/gldemo.html

The repo: https://github.com/Atomotron/ld47-prep