Idea: A tiny neural network that you can watch train and run

It'd be neat to have a tiny neural network in a browser that you can watch train and then run. Ideally it should be based on the generative pre-trained transformer architecture. And it should allow the user to see the weights, and then hand modify them if desired, and then re run. The inference would be slowed down so that we can observe it. Has anyone built this? I believe it'd be excellent as a way to give people a better intuition for larger networks.