Getting started with planets

Adding planets:

You click once to place the planet in a given location. Then move the mouse again, and you'll see a vector pointing from the planets location to the pointer. This is the initial velocity. Click again to set this.

Note that you can simply double-click to make a zero-velocity planet.

Keeping planets on-screen

recenter

on the center of mass and zero out the central velocity, by pressing the space bar.

pan

to follow the planets, by using the arrow keys

zoom in/out

by using the +/- keys. If you think you've lost planets, you can zoom way out, and eventually you'll seem them again. Just press the - key and hold it.

Saving and loading universes

You can save a configuration by typing "s" and then any other single character. Type "l" and that character to load the universe. Try l9 to load an interesting universe that comes with the distribution.

Fun things

undo and goback

"u" undoes the last planet addition, which is good for fixing mistakes. "g" goes back to just after the last planet addition which is nice for replaying interesting situations. You can undo arbitrarily many steps.

control panel

Press "k" to call up the control panel. This lets you see and control a number of configuration options, and see some of the state of the system.

Traces

Press "t" to toggle tracing, "d" to double trace length, and "h" to half trace length

Bouncing

Press "b" to toggle force bouncing, and "B" to toggle true bouncing

C-O-M following

You can track the center of mass of a subset of planets by dragging a box around them. "x" cancels the COM tracking. This is useful, for instance, if you want to track the moon and earth only of a moon-earth-sun system.