it would be better if the color could be mapped by some attributes

[milanglacier]

from the current documentation, I suppose the colors of the circles are determined by the hierarchic levels, it would be better if the colors could be mapped by a specific attributes in the data.tree structure.
Besides, if the graph could be moved by the moving of the mouse or scroll and not limited by only clicking the circles, it would be more interactive, and the overlaps of the letters problem could be somehow relieved.
whatever, still thanks a lot for wrapping a very-easy-to-use d3.js package to R!