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    <title>Getting started with planets</title>
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    <h1>Getting started with planets</h1>
    
    A quick tutorial to get you started

    
    <h3>Adding planets:</h3> Press "a" to add a planet.  That will
    attach a circle to your pointer, indicating the size of the planet.
    That size can be changed by pressing a number 0-9, and can also be
    adjusted up and down by a small percentage using the up and down
    arrows.
	<p>
	  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.
	<p>
	  Note that you can simply double-click to make a zero-velocity
	  planet.
    </p>

    <h3>Keeping planets on-screen</h3>

    There are a few ways of preventing planets from disappearing from
    view.  You can:
    <dl>
      <dt><b>recenter</b>
      <dd>on the center of mass and zero out the central velocity, by
	pressing the space bar.
      <dt><b>pan</b>
      <dd>to follow the planets, by using the arrow keys
      <dt><b>zoom in/out</b>
      <dd>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.
    </dl>
    
    <h3> Saving and loading universes </h3>
    <p>
      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.

    <h3> Fun things </h3>
    <dl>
      <dt><b>undo and goback</b> <dd> "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.

      <dt><b>control panel</b>
      <dd> 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.  

      <dt><b>Traces</b>
      <dd> Press "t" to toggle tracing, "d" to double trace length, and "h"
	to half trace length
	
      <dt><b>Bouncing</b>
      <dd> Press "b" to toggle force bouncing, and "B" to toggle true bouncing

      <dt><b>C-O-M following</b>
      <dd> 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.
    </dl>

    More information can be found in the Keybindings.txt file in the distribution.

    <hr>
    <address><a href="mailto:yminsky@cs.cornell.edu">Yaron M. Minsky</a></address>
<!-- Created: Sun Jan  6 23:25:18 EST 2002 -->
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Last modified: Mon Jan  7 11:21:44 EST 2002
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