After reset, the simulation should be in "live" mode, not "paused".
Add a movable PE=0 level (graphic & model).
"Location" radio button should be disabled when not in an exact location.
Wash out the images, they are still distracting.
Pie Chart legend in top right, only when pie chart is on.
Don't have the energy vs. position graph fade while the simulation is paused.
Put coeff/friction in an advanced button.
Rescalable Energy vs Position graphs.
Have to push record to graph (add a wiggle me).
Record bug:
	Record, then live, then record resets to last record state.	
Add clipping to energy vs position plot.
Add game-ish modes to sk8r application
	. 2-skater mode
	. Grab the apple?
	. Jump the buses?
Bug: When user drags track that skater is resting on, the skater doesn't move with it.
[internal] Figure out the meaning of the magic grab number in EnergyConservationModel

low priority:
User-selectable skater/vehicle graphics.
Crashing skater?