From 73a4268fa0a0a42a4b75ba8e3946a825519eca24 Mon Sep 17 00:00:00 2001
From: Michael Barlow <m.barlow12@gmail.com>
Date: Mon, 10 Dec 2018 16:08:36 -0700
Subject: [PATCH] 'mass' -> 'density' when constant radius is checked, see
 phetsims/gravity-force-lab#123

---
 .../view/GravityForceLabBasicsScreenView.js                   | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/js/gravity-force-lab-basics/view/GravityForceLabBasicsScreenView.js b/js/gravity-force-lab-basics/view/GravityForceLabBasicsScreenView.js
index 855c075..3d02a7d 100644
--- a/js/gravity-force-lab-basics/view/GravityForceLabBasicsScreenView.js
+++ b/js/gravity-force-lab-basics/view/GravityForceLabBasicsScreenView.js
@@ -65,6 +65,7 @@ define( function( require ) {
   var spherePositionHelpTextString = ISLCA11yStrings.spherePositionHelpText.value;
   var massControlsLabelString = GravityForceLabA11yStrings.massControlsLabel.value;
   var massControlsHelpTextBillionsString = GravityForceLabA11yStrings.massControlsHelpTextBillions.value;
+  var massControlsHelpTextDensityBillionsString = GravityForceLabA11yStrings.massControlsHelpTextDensityBillions.value;
   var forceValuesCheckboxHelpTextString = ISLCA11yStrings.forceValuesCheckboxHelpText.value;
   var constantSizeCheckboxHelpTextString = GravityForceLabA11yStrings.constantSizeCheckboxHelpText.value;
   var distanceCheckboxHelpTextString = GFLBA11yStrings.distanceCheckboxHelpText.value;
@@ -171,6 +172,9 @@ define( function( require ) {
     } );
     massControlsNode.addChild( massControlBox );
 
+    model.constantRadiusProperty.link( function( constantRadius ) {
+      massControlsNode.descriptionContent = constantRadius ? massControlsHelpTextBillionsString : massControlsHelpTextDensityBillionsString;
+    } );
 
     var checkboxItems = [
       new ISLCCheckboxItem( forceValuesString, model.forceValuesProperty, {