Click mouse or click + <Alt> to Zoom In x2
Click mouse + <Ctrl> to Zoom Out
<Shift> to modify Zoom In/Out x4
Steps - number of steps in animation
It - max iterations number
Delay - delay between two frames rendering
1. Choose an appropriate "delay" for your PC.
2. To restart an applet "reload" it (with <Shift> under Netscape).
All applets are optimized for 1GHz PC (You could pay Intel or AMD 100$ for they will make even more powerful chips :)
See also comments to the Boundary Tracing and the Distance Estimator algorithms.