O(n*log(n)) assembly of edges into contours
good color picker
crude DXF, HPGL import
a request to import a plane thing
make export assemble only contours in same group
make export rewrite fill color same as stroke color
choose split point closest to mouse pointer

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rounding, as a special group
associative entities from solid model, as a special group
better level of detail
some kind of import
faster triangulation
loop detection
IGES export
incremental regen of entities