Live demo: http://voxel.github.io/voxelmetaverse/
Source code: https://github.com/voxel/voxelmetaverse
I had big ideas for it but didn't get too far, after several years of working on it. Just published a retrospective today: https://medium.com/@deathcap1/6-years-after-6-months-of-voxe... - it could be developed much, much further.