Some sample universes have been around for a long time .
However, the newer Java versions demonstrate the Rart™
concept as well as the use of the Rart Development
Kit, RDK 3.0. You can here observe and play with selected universes or
observe a Continuous Demo
These universes, except the Demo, are run using the latest
RRlet release, 2.5. RRlet 2.5 was revised to allow the observer
to maximize the window and, using a long mouse click, get a pop up menu
to among other things modify the parameters.
Note: In this environment the
universe, when started in the browser, opens in a new expandable
When this window is closed,
using the close
button, you get a browser window with some rests of the
observed universe. Hit the browsers back
button to get back to where
you started your selection to observe the universe.
This variation of the older Eggs was added 2010. It
foreground colors in steps and background color continuously.
goes through a cycle of color changes in an hour, but this can be
changed. It also has built in probabilities for
other surprises. See the Egg2 universe
This is one of my first universes (originally
1988-89). It demonstrates how very simple
shapes interact to form surprising and interesting patterns. See the Eggs universe and make sure to try different
This universe is patterned after an early screen saver. While
in general screen savers meet the requirements for a Rart universe,
randomness etc. the main difference is in the Java environment which
encourages the display of the universe over the Internet using almost
any Java enabled browser whereas screen savers usually are programmed
code specific to the operating system and computer.. In the Polygons
universe the observer can
modify the number of corners and the number of lines as well as color.
See the Polygons universe.
The universe is my first attempt to model some aspect of
reality, in this case the snowflake. The symmetric branching of the
snowflake is in itself a wonder and causes flakes to be different for
simple physical reasons. This universe grows the flakes according to
rules which apply until the limit of resolution of the screen is
achieved. Originally I programmed the
Flakes universein 1998.It was later modified to
serve as an animated
Christmas card. This version, with suitable and modifiable text went
in 2006. One parameter, "Complexity", influences the nature of the
growing flake by shortening the length from a branching point to the
Originally this universe was designed to test the
incorporating of external files into a Rart universe. In this case
three balls in three different colors are provided as GIF-images. As
I played around I added bouncing of the balls as well as the ability to
show trace of the balls and a parameter for gravity which makes the
balls fall down or up. Observe the ThreeBalls
universe and try out the trace capability.
This universe is closely related to the ThreeBalls universe.
I took out the bouncing of colliding balls and added Newtonian
gravitation, i.e. each body in the universe attracts (or repels) every
other with a force proportional to the product of the masses and
inversely proportional to the square of the distance. If anything, this
universe shows how difficult it is to end up with a stable planetary
system. The parameter "Solar System Configuration" offers a choice of
configurations including one with a double sun.
RRlet, demo version .
environment, is programmed to run
in browsers that conform to JDK 1.1+. It should be viewable in almost
any browser (See the Rart
Homepage about how to enable Java for various browsers with Java
In this continuously running demo you normally get one of
simple universes, text universes with explanatory
text displayed for 10-15 seconds. In demo-mode a universe is then
selected at random to run from anywhere between
30 and 90 seconds. When a universe is running in demo-mode, a long
click initiates a series of dialogs allowing
you to change parameters. A long click also adds about five minutes of
running time so you can play around some
more without being interrupted. On a short click, you get a new
selection of universe with new randomly selected
In this older version of the rartrunner you can not
Maximize the applet window but use a predefined window
size. We have provided window sizes 800 x 480 pixels and 1200 x 500
The applet tag looks as follows for those that are
alt="( With a java enabled browser you would see animation here)">
<PARAM NAME="UNIVERSE" VALUE="A2">
<PARAM NAME="DEBUG_LEVEL" VALUE="0">