Great project. One thing that is masked by the tree view though is that there were indeed countless other languages being spoken besides Proto-Indo-European. It's just the one that gave rise to today's Indo-European languages. But back then it wasn't alone, but just one of many, some related to it and some more distant from it. Kinda similar to how it works today. It had dialects, it was in motion and change, it had earlier versions etc. etc.