old_contents: //Icon that just shows one value if the property is selected or another value if the property is deselected
  define( function( require ) {
    "use strict";
  
    var Node = require( 'SCENERY/nodes/Node' );
    var inherit = require( 'PHET_CORE/inherit' );
  
    function ToggleNode( off, on, property ) {
      var toggleNode = this;
      Node.call( this, {} );
      property.link( function( m, newValue ) { toggleNode.children = [newValue ? on : off]; } );
    }
  
    inherit( ToggleNode, Node );
  
    return ToggleNode;
  } );
new_contents: //Icon that just shows one value if the property is selected or another value if the property is deselected
  define( function( require ) {
    "use strict";
  
    var Node = require( 'SCENERY/nodes/Node' );
    var Path = require( 'SCENERY/nodes/Path' );
    var Shape = require( 'KITE/Shape' );
    var inherit = require( 'PHET_CORE/inherit' );
  
    function ToggleNode( off, on, property ) {
      var toggleNode = this;
      Node.call( this, {} );
      var background = new Path( {shape: Shape.bounds( on.bounds.union( off.bounds ) )} );
      property.link( function( m, newValue ) { toggleNode.children = [background, newValue ? on : off]; } );
    }
  
    inherit( ToggleNode, Node );
  
    return ToggleNode;
  } );
subject: make sure the toggle icon is large enough to hold both on and off content