Instructions - Click Anywhere to Hide

The marbles in the trays control the shape of the fern. You can click inside a tray to set the marble position. You can also click the green triangular buttons to nudge a tray's marble. When you stop changing things for 3 seconds, the applet will draw the new fractal. When the applet decides the drawing is finished, it draws a gray rectangle around it.

Frond Shape

Controls the shape of the overall frond. Move the marble left and right to affect frond taper. Move the marble up and down to affect frond density.

Frond Curvature & Rotation

Controls the curvature and rotation of the overall frond. At the center of the tray the frond is straight. Move up and down to bend the frond. Move left and right to "twist" the frond.

Leaflet Scale

Controls the scaling of the individual leaflets. Move the marble up and down to affect their height. Move the marble left and right to affect their width.

Leaflet Angle

Controls the angle between the leaflets and the stem. Move the marble up and down to affect the leaflets on top. Move it left and right to affect the leaflets on the bottom.

Leaflet Placement

Controls the placement of the leaflets along the stem. Move the marble up and down to affect the leaflets on top. Move it left and right to affect the leaflets on the bottom.

Shading Balance

Controls the rate at which different parts of the fractal darken. Moving the marble up makes the upper leaflets darker. Moving the marble right makes the lower leaflets darker.

As the marbles move toward the edges of their trays, the parameters they control may move beyond the range in which you get something that looks like a fern. Sometimes what you get instead is interesting in its own right, and sometimes perhaps not. As a guide, the darker tiles in the tray bottoms show the areas where you're most likely to produce a fern fractal, but this doesn't mean you should avoid going outside them.

Clicking inside the display area regenerates the image centered on the point clicked. Shift-click to zoom in. Ctrl-click to zoom out. Or use the square + and - buttons. The other square buttons toggle between green and greyscale, and turn the fern stem on and off.

Because every leaflet is a copy of the whole frond, the result you get from moving a marble can be hard to predict. Experiment with each tray. Make small changes and try to understand the result. Can you learn to think fractally?