Drag red points (circles) into a triangles. Drag green point to make a triangle, so you have two triangles connected into a pyramid. Redrag for overlap. Draws fractal triangle between the points, wherever you place them. You can redrag to make art. Spacebar to hide circles. Flag to reset. Automatic set to 1 doesn't let you make your own art.
Drag red circles, repeat. Draws "Sierpinski" triangles. Each is fractal even when triangle is distorted. Pen uses darn little code. Circle sprites use more code. Aggregates of triangles really break the symmetry, often in a beautiful way.