Constructomatic

Constructomatic presents you with a blank slate for building geometric constructions. There is a list of possible items to add on the lower left. You can always create a free point, that is, a point you can move wherever you want, but as you build and select points, lines and circles, the list grows to show what else you can build from what you have selected. (For example, if you have two points selected, you can build a line segment between them, a ray or an open ended line that joins them.) See below for more details on what you can create and how to use them.

Click on an item to select or unselect it. You can drag free points, points on lines, points on circles and line segments connecting two free points. You can drag the screen to pan the image and use the plus and minus icons on the lower right to zoom in and out.

You can delete the selected item or items and everything that depends on them by using the delete button, a red cross. You can show and hide items by selecting on them and using the toggle show and hide button. There is a toggle show all button to the lower right that toggles between showing all items and only showing those items not explicitly hidden.

There isn't much to the program, but there is a lot you can do with it. All it takes is some geometry and some imagination.

To download the program:

for MacOS - DOWNLOAD - Works on 10.6.6. Probably works with most recent versions thanks to RealBasic.
for Windows - DOWNLOAD - Untested - we don't have a Windows machine.
for Linux - DOWNLOAD - Untested - we don't have a Linux machine either.

What the little icons mean

Icon	What it works with	What it does
	Always available	Creates a single unconstrained point
	Two points	Creates a line segment connecting the two selected points
	Two points	Creates a ray starting at the first of the two selected points selected and running through the second point and beyond - Order Dependent
	Two points	Creates an open ended line passing through the selected two points
	Two points	Creates a point located midway between the two selected points
	Two points	Creates a circle with the first selected point as its center and the distance between the two points as its radius
	Three points	Creates a circle that passes through the three selected points
	Three points	Creates a point at the center of the circle that would run through the three selected points
	Three points	Creates a ray (i.e. an open ended line) from the second point selected that bisects the angle defined by three points as selected in order
	One line	Creates a point that is constrained to lie on the selected line - You can drag it, but it must stay on the line.
	One circle	Creates a point that is constrained to lie on the selected circle - You can drag it, but it must stay on the circle.
	One point and one line segment	Creates a circle centered at the selected point with a radius equal to the length of the selected line segment
	One point and one line	Creates a line parallel to the selected line passing through the selected point
	One point and one line	Creates a line perpendicular to the selected line passing through the selected point
	Two lines, two circles or a line and a circle	Creates one or two points at the intersection of the two selected objects - These points will only be visible if there is an appropriate defining intersection.
	One or more objects of any type	Deletes the selected objects and any objects that depend on their definition
	One or more objects of any type	Toggles whether they are to be shown or hidden
	On the right, always visible	Toggles whether all items are shown or only those not explicitly hidden
	On the right, always visible	Toggles the black background and white background color scheme
	On the right, always visible	Zooms in
	On the right, always visible	Zooms out

Some examples

	This is the construction for the incenter of a triangle defined by three points. The incenter is the intersection of the angle bisectors which defines a point equidistant from the sides. It is the center of the inscribed circle. Download the example.
	This is the construction for the centroid of a triangle defined by three points. The centroid is the intersection of the three medians, the lines connecting each vertex to the midpoint of the side opposite. It is the center of balance of the triangle. Download the example
	This is the construction for the orthocenter of a triangle defined by three points. The orthocenter is the intersection of the perpendicular bisectors of each side and is equidistant from the vertices. It is the center of the circumscribed circle. Download the example
	This is the construction for a regular pentagon based on a circle as defined by three points. Download the example