drag the corners of the polygon to move them, drag the edges to add a new corner. Doesn't handle self-intersecting polygons Incompatible with sulurous and phosphorus. If the project fills a polygon incorrectly, please turn on debug mode and send me an uploaded screenshot (via for instance imgur). If the project crashes, please restart it, turn on debug mode, try to recreate the bug, and send me a screenshot.
Credit to @raucket for inspiration Credit to @theLogFather for triangle filler and angle calculation update log; v3.0; redid first algorithm (blue lines in debug mode) v2.1; fixed a bug that could cause the poly to fill incorrectly v2.0; fixed a bug that could cause the poly to fill incorrectly and crash the project v1; released