I've decided to build a simple 2D framework for building multiplayer/MMO games (similar scope to Agar.io), I have significant experience in building multiplayer engines for windows/linux but I have never touched web. If you have any advice on libraries and development technologies, or general advice, I would greatly appreciate it.
My current tech stack (if you think this is naive feel free to call me out, as I am indeed naive.):
Physics: Box2D or simila