It's a nice beginning.

Some obvious features which I missed:

- nodes tool should want to snap begin/end nodes together when editing (and the snap distance could be larger when initially creating, esp. w/ the pencil tool)

- rather than a Nodes tool for editing, something like to Wick Editor's Flash/Futurewave Smarksetch pull/push deforming would be much more mobile friendly

- if corner rounding doesn't work on polygons it should be hidden/disabled