Probably my favorite structure is that you can tile the plan with similar quadrilaterals. All of these are dilations of ABCD. This is a new version of an [url=https://www.geogebra.org/m/rMgQ7FXM]old applet[/url].[br][br]If you download the applet, there's a simple tool nxtq that will build your own. Just select the four vertices and voila!