Click the Share button at top-right corner of app frame. Select appropriate tab. Enter details. Check the box indicating you want to 'Publish source code'. Click the Share button.

Wow -- I had no idea you were talking about a thin line of green. As such, you might be better off adding Ground objects into the world -- just invisible rectangles whose top edges line up with the horizontal green lines. The Ground actors can then be used to prevent the "falling through" issue. Let us fix the "subclass doesn't change" issue later and worry about the "falling through" right now.