WHAT IT DOES
------------
This program simulates sand flowing through a series of user
configurable pipes.  The program will eventually be extended
to model the more complicated process of water flow.

HOW TO USE IT
-------------

Buttons
~~~~~~~

Setup		Clears the screen and creates the pipe icons 
		along the left side edge of the screen

Build		Activates building mode which allows the user
		to create pipes on the screen, and move the 
		sand faucet to the desired location.

Move-sand	Turns the sand flow mode on

Add-sand	Adds fifty sand particles to the faucet

eliminate-sand	Eliminates all sand particles from the screen	

Sliders
~~~~~~~

Rain		When set as 0, the sand flows from the faucet.
		When set as 1, the sand flows randomly from
		anywhere on the top edge of the screen.

Conflow		When set as 0, the sand does not "wrap" around
		when it reaches the bottom of the screen.
		Instead it goes back into the faucet or rains
		down randomly.  When set as 1, the sand 
		"wraps" back to the top of the screen.


Build Mode
~~~~~~~~~~

In build mode, highlight any of the five red construction 
icons on the left side of the screen.  The bottom icon is an
eraser.  Then to create a piece of pipe click somewhere in
the black space to the right of the icons.  If you hold the
mouse button down, the piece will rotate.  If you click on
the blue arrow at the bottom of the screen the size of the
pipes will change.


EXTENDING THE MODEL
-------------------

	-  Create more constructions

	-  Create "active" constructions that affect or 
	   measure the particles that flow through them.
           (Examples: changing the color or teleporting it 
	    to another location on the screen)