Wolfram Technology Guide: Dynamic Interactivity  previous | next 
Dynamically Move Points in Graphics
Mathematica immediately allows you to set up a modifiable number of movable points that can be used as direct controls.
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Click for copyable input
Manipulate[

 Graphics[{Opacity[.4, Red], Polygon[p[[Last[FindShortestTour[p]]]]]},

   PlotRange -> 1],

 {{p, RandomReal[{-1, 1}, {15, 2}]}, {-1, -1}, {1, 1}, Locator}]
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