This is a bitmap-based flash which uses a particular recursion rule that resembles the serpinski triangle. However, you are allowed you add your own starting points anywhere you like on the screen before you run the simulation. You can reset with the red button and run with the white one. You can also add points during/after the simulation has swept from the top down and run again for extra results. Little offsets create a sea of triangles...

You can now define your own rules in a menu, allowing hundreds of combinations of patterns.
Download the fullscreen (newest version) here.

nice.

If you like it, here's fullscreen for mesmerizing awesomeness.

(download the attachment). Ok, I don't know how large your screen is, tell me if that's too big.

that rocks.

The ability to define your own recursion rules has been added.

Click the boxes below each set of three (these represent the possible pixel combinations of the three pixels that can be above any given pixel, and whether they output a white or a black pixel. By default they are all black, so you must change some). Press the close button when you're done, then click the screen to add one or more seeds. Then press the white button to run. To open the menu again, press the red button.

To download the fullscreen updated version, download the attachment.

EDIT: Interface redesign.