Konstrukt
Konstrukt is an SVG + ECMAScript application for compass and straightedge construction. It's not too unintuitive to use, once you know what the controls are:
- to draw a straight line through two marked points
- press the v key and click on the two points
- to draw a circle centered at one marked point through another
- press the c key and click on the two points (the first of which is the center)
- to delete a marked point and all edges through it
- press the x key and click on the point (tip: you might create extra lines and circles for the purposes of deleting at an intersection)
- to move the viewpoint
- click on empty space to center the view on that position
- to zoom in
- press the PgUp key
- to zoom out
- press the PgDn key
I've mostly been using it to play around trying to tile the Poincaré Disk (PDF) model of hyperbolic geometry, trying to emulate the Artful Mathematics (PDF) of M.C. Escher, with a healthy dose of Euclid's Elements thrown in for practice.
I've also been working on a presentation (still unfinished) on this topic for SummerLAB in Gijón.