Edit in JSFiddle

<script type="text/paperscript" canvas="myCanvas">
    var circle = new Path.Circle(new Point(100,70),50);
    circle.strokeColor = "black";
    
    
    var rect = new Rectangle(new Point(200,50),new Point(300,100));
    
    var path = new Path.Rectangle(rect);
    path.fillColor = "#ccc";
    path.selected = true;
    
    
    var rect2 = new Rectangle(new Point(50,200),new Point(200,250));
    var cornerSize = new Size(20,20);
    var path2 = new Path.RoundRectangle(rect2,cornerSize);
    path2.fillColor = "#85EB6A";
    
    var triangle = new Path.RegularPolygon(new Point(80,370),3,50);
    triangle.fillColor = "#FF9640";
    triangle.selected = true;
    
    var decahedron = new Path.RegularPolygon(new Point(200,370),10,50);
    decahedron.fillColor = "#FFB273";
    decahedron.selected = true;
    
    
    
</script>

<canvas id="myCanvas" resize></canvas>