What Was Missing

The core mechanics of this simulation I feel are solid and therefore I did not make any changes to the physics.  What was cumbersome and incomplete was the user interface.  It wasn't clear which fields were editable and which were not.  There was also illustration of the ellipse geometry elements such as the major or minor axes.  While the simulator was useful for demonstrating the relationship between orbital energy and eccentricity, and you could use the data to verify Kepler's Third Law, the simulator's utility as a student resource outside of a classroom lecture was limited.  

What Was Added

• Editable fields (initial velocity and initial distance) are shown in green.
• Calculated fields are shown in amber.
• A new panel allowing the ellipse geometry features to be toggled on or off.
  • Major axis (green)
  • Minor Axis (cyan)
  • Distance to each focus (purple)
• Text display of Kepler's Three Laws:
  • K - Toggles the Kepler's Laws text panel on or off.
  • 1 - Toggles the First Law text on or off.
  • 2 - Toggles the Second Law text on or off.
  • 3 - Toggles the Third Law text on or off.

What Still Needs Done

The main display of orbital parameters is a static image rather than an a collection of editable elements.  This was fine when it was the only UI element on the screen, but now with the inclusion of the Ellipse Geometry panel, its appearence is inconsistent.  The display fields for the actual values will be kept, but the labels and background, which are a single image, need to be redone to be individual elements that can be designed to better match the style of the Ellipse Geometry panel.

I also plan on adding a series of buttons on the right side for each of the nine planets, the largest asteroid Ceres, and Halley's Comet.  Clicking each of these buttons will set the initial velocity and position for each of these objects so that they can be modeled by the simulator showing the range of eccentricities and orbital periods for these objects.