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UX on the other hand...I hate it when sites hijack my key commands for moving backwards and forwards in my browser history. Please don't do this!

For me it's horrible, some scripts makes the scroll very choppy, unusable... had to disable scripts just to be able to normally scroll :-(

I think the diagrams look very similar to what Keenan Crane uses in his papers, perhaps they used that tool. I think his students have now fleshed it out for general use.