diff --git a/js/game/model/CountingGameLevel.ts b/js/game/model/CountingGameLevel.ts
index 1f308468..d7c0a8b6 100644
--- a/js/game/model/CountingGameLevel.ts
+++ b/js/game/model/CountingGameLevel.ts
@@ -32,7 +32,7 @@ class CountingGameLevel extends NumberPlayGameLevel {
     super( levelNumber, numberPlayStrings.counting, LEVEL_INPUT_RANGE );
 
     // whether objects should be able to be grouped
-    this.groupObjects = levelNumber === 2;
+    this.groupObjects = ( levelNumber === 2 );
 
     this.objectsPlayArea = new OnesPlayArea( this.challengeNumberProperty, new Vector2( 0, 0 ), {
       isOnes: false,
diff --git a/js/game/model/NumberPlayGameLevel.ts b/js/game/model/NumberPlayGameLevel.ts
index 39f752b0..4614d2c1 100644
--- a/js/game/model/NumberPlayGameLevel.ts
+++ b/js/game/model/NumberPlayGameLevel.ts
@@ -49,7 +49,7 @@ abstract class NumberPlayGameLevel {
     // guessed the answer
     this.isChallengeSolvedProperty = new BooleanProperty( false );
 
-    // the random number generated to create a subitized representation for
+    // the random number generated to create a representation for
     this.challengeNumberProperty = new NumberProperty( this.getRandomChallengeNumber(), {
       numberType: 'Integer',
       range: this.challengeRange
@@ -100,6 +100,9 @@ abstract class NumberPlayGameLevel {
     this.challengeNumberProperty.value = newChallengeNumber;
   }
 
+  /**
+   * Generate a random challenge number that is in the defined challenge range.
+   */
   private getRandomChallengeNumber(): number {
     return dotRandom.nextIntBetween( this.challengeRange.min, this.challengeRange.max );
   }
diff --git a/js/game/model/SubitizeGameLevel.ts b/js/game/model/SubitizeGameLevel.ts
index 4ee13d9e..71277236 100644
--- a/js/game/model/SubitizeGameLevel.ts
+++ b/js/game/model/SubitizeGameLevel.ts
@@ -38,12 +38,12 @@ class SubitizeGameLevel extends NumberPlayGameLevel {
     this.subitizer.newChallenge();
   }
 
-  public reset() {
+  public reset(): void {
     super.reset();
     this.subitizer.reset();
   }
 
-  public step( dt: number ) {
+  public step( dt: number ): void {
     this.subitizer.step( dt );
   }
 }
diff --git a/js/game/model/Subitizer.ts b/js/game/model/Subitizer.ts
index bddb666f..df66f1fc 100644
--- a/js/game/model/Subitizer.ts
+++ b/js/game/model/Subitizer.ts
@@ -188,7 +188,7 @@ class Subitizer {
     // how long the shape is visible when shown, in seconds. This is a derived Property instead of a constant because
     // the time that the shape is shown is increased if the user gets the answer wrong multiple times.
     this.timeToShowShapeProperty = new DerivedProperty( [ numberOfAnswerButtonPressesProperty ],
-      ( numberOfAnswerButtonPresses: number ) => {
+      numberOfAnswerButtonPresses => {
         if ( numberOfAnswerButtonPresses > NumberPlayConstants.NUMBER_OF_SUBITIZER_GUESSES_AT_NORMAL_TIME ) {
           return this.timeToShowShapeProperty.value + NumberPlayConstants.SHAPE_VISIBLE_TIME_INCREASE_AMOUNT;
         }
@@ -397,13 +397,17 @@ class Subitizer {
     // randomly pick between modifying the top row or bottom row
     if ( dotRandom.nextBoolean() ) {
       const sliceIndex = points.length - challengeNumber;
-      reducedPoints = points.slice( sliceIndex ); // remove extra points from the top row, left side
+
+      // remove extra points from the top row, left side
+      reducedPoints = points.slice( sliceIndex );
 
       // remove extra points from the top row, right side
       reducedShiftedPoints.splice( numberOfColumns - sliceIndex, sliceIndex );
     }
     else {
-      reducedPoints = points.slice( 0, challengeNumber ); // remove extra points from the bottom row, right side
+
+      // remove extra points from the bottom row, right side
+      reducedPoints = points.slice( 0, challengeNumber );
 
       // remove extra points from the bottom row, left side
       reducedShiftedPoints.splice( points.length - numberOfColumns, points.length - challengeNumber );
diff --git a/js/game/view/CountingGameLevelNode.ts b/js/game/view/CountingGameLevelNode.ts
index df17c813..6e2b3a3a 100644
--- a/js/game/view/CountingGameLevelNode.ts
+++ b/js/game/view/CountingGameLevelNode.ts
@@ -36,7 +36,9 @@ class CountingGameLevelNode extends NumberPlayGameLevelNode<CountingGameLevel> {
                layoutBounds: Bounds2,
                visibleBoundsProperty: Property<Bounds2> ) {
 
-    super( level, levelProperty, layoutBounds, visibleBoundsProperty, { statusBarFill: NumberPlayColors.countingGameColorProperty } );
+    super( level, levelProperty, layoutBounds, visibleBoundsProperty, {
+      statusBarFill: NumberPlayColors.countingGameColorProperty
+    } );
 
     // create and add the answerButtons
     this.answerButtons = new NumberPlayGameAnswerButtons( level, this.pointsAwardedNodeVisibleProperty, () => {
@@ -121,7 +123,7 @@ class CountingGameLevelNode extends NumberPlayGameLevelNode<CountingGameLevel> {
       tenFramePanel.visible = !isObjects;
     } );
 
-    // start a challenge
+    // start a new challenge
     super.newChallenge();
   }
 
diff --git a/js/game/view/NumberPlayGameLevelNode.ts b/js/game/view/NumberPlayGameLevelNode.ts
index 85bc4e8b..f8616832 100644
--- a/js/game/view/NumberPlayGameLevelNode.ts
+++ b/js/game/view/NumberPlayGameLevelNode.ts
@@ -67,7 +67,7 @@ abstract class NumberPlayGameLevelNode<T extends NumberPlayGameLevel> extends No
       levelNumber: level.levelNumber
     } ), {
       font: new PhetFont( 21 ),
-      maxWidth: 650 // determined empirically
+      maxWidth: 650
     } );
 
     // bar across the top of the screen
@@ -81,7 +81,7 @@ abstract class NumberPlayGameLevelNode<T extends NumberPlayGameLevel> extends No
         levelProperty.value = null; // back to the level-selection UI
       }
     } );
-    // color the back button in the statusBar yellow
+    // color the backButton in the statusBar yellow and increase its touch area
     const backButton = this.statusBar.children[ 1 ].children[ 0 ];
     // @ts-ignore
     backButton.baseColor = Color.YELLOW;
@@ -115,7 +115,7 @@ abstract class NumberPlayGameLevelNode<T extends NumberPlayGameLevel> extends No
 
     // create and add the pointsAwardedNode which is shown when a correct guess is made on the first answer button press
     const starNode = new StarNode( { value: 1, scale: 1.5 } );
-    const pointsNode = new Text( '+1', { font: new PhetFont( 44 ), fill: Color.BLACK } );
+    const pointsNode = new Text( numberPlayStrings.plusOne, { font: new PhetFont( 44 ), fill: Color.BLACK } );
     const pointsAwardedNode = new HBox( {
       children: [ pointsNode, starNode ],
       spacing: 10,
diff --git a/js/game/view/NumberPlayGameScreenView.ts b/js/game/view/NumberPlayGameScreenView.ts
index a2888b44..c7776595 100644
--- a/js/game/view/NumberPlayGameScreenView.ts
+++ b/js/game/view/NumberPlayGameScreenView.ts
@@ -28,7 +28,6 @@ const TRANSITION_OPTIONS = {
 class NumberPlayGameScreenView extends ScreenView {
 
   private readonly levelNodes: Array<SubitizeGameLevelNode | CountingGameLevelNode>;
-  private readonly subitizeLevelNodes: SubitizeGameLevelNode[];
 
   constructor( model: NumberPlayGameModel, tandem: Tandem ) {
 
@@ -47,11 +46,11 @@ class NumberPlayGameScreenView extends ScreenView {
       new CountingGameLevelNode( level, model.levelProperty, this.layoutBounds, this.visibleBoundsProperty ) );
 
     // create the level nodes for the 'Subitize' game
-    this.subitizeLevelNodes = model.subitizeLevels.map( level =>
+    const subitizeLevelNodes = model.subitizeLevels.map( level =>
       new SubitizeGameLevelNode( level, model.levelProperty, this.layoutBounds, this.visibleBoundsProperty ) );
 
     // store all level nodes in one place for easy iteration
-    this.levelNodes = [ ...countingLevelNodes, ...this.subitizeLevelNodes ];
+    this.levelNodes = [ ...countingLevelNodes, ...subitizeLevelNodes ];
 
     // create the transitionNode which handles the animated slide transition between levelSelectionNode and a level
     const transitionNode = new TransitionNode( this.visibleBoundsProperty, {
@@ -59,8 +58,8 @@ class NumberPlayGameScreenView extends ScreenView {
       cachedNodes: [ levelSelectionNode, ...this.levelNodes ]
     } );
 
-    // Transition between levelSelectionNode and the selected level when the model changes.
-    // A null value for levelProperty indicates that no level is selected, and levelSelectionNode should be shown.
+    // Transition between the levelSelectionNode and the selected level when the model changes.
+    // if levelProperty has a null value, then no level is selected and levelSelectionNode will be displayed.
     model.levelProperty.lazyLink( level => {
       this.interruptSubtreeInput();
 
diff --git a/js/game/view/SubitizeGameLevelNode.ts b/js/game/view/SubitizeGameLevelNode.ts
index bf76a6bd..72784ac8 100644
--- a/js/game/view/SubitizeGameLevelNode.ts
+++ b/js/game/view/SubitizeGameLevelNode.ts
@@ -26,7 +26,9 @@ class SubitizeGameLevelNode extends NumberPlayGameLevelNode<SubitizeGameLevel> {
                layoutBounds: Bounds2,
                visibleBoundsProperty: Property<Bounds2> ) {
 
-    super( level, levelProperty, layoutBounds, visibleBoundsProperty, { statusBarFill: NumberPlayColors.subitizeGameColorProperty } );
+    super( level, levelProperty, layoutBounds, visibleBoundsProperty, {
+      statusBarFill: NumberPlayColors.subitizeGameColorProperty
+    } );
 
     // create and add the answerButtons
     this.answerButtons = new NumberPlayGameAnswerButtons( level, this.pointsAwardedNodeVisibleProperty, () => {
diff --git a/js/game/view/SubitizeLoadingBarNode.ts b/js/game/view/SubitizeLoadingBarNode.ts
index 359680a2..944a0eac 100644
--- a/js/game/view/SubitizeLoadingBarNode.ts
+++ b/js/game/view/SubitizeLoadingBarNode.ts
@@ -29,13 +29,14 @@ const ANIMATION_DELAY = 0.1; // in seconds
 class SubitizeLoadingBarNode extends Node {
 
   private readonly isLoadingBarAnimatingProperty: BooleanProperty;
-  private readonly newChallenge: () => void;
+  private readonly newChallengeCallback: () => void;
   private loadingBarAnimation: Animation | null;
   private readonly loadingBarWidthProperty: NumberProperty;
 
-  constructor( newChallenge: () => void, isLoadingBarAnimatingProperty: BooleanProperty ) {
+  constructor( newChallengeCallback: () => void, isLoadingBarAnimatingProperty: BooleanProperty ) {
     super();
-    this.newChallenge = newChallenge;
+
+    this.newChallengeCallback = newChallengeCallback;
     this.isLoadingBarAnimatingProperty = isLoadingBarAnimatingProperty;
 
     // the rectangle that is a border to the filled rectangle
@@ -115,7 +116,7 @@ class SubitizeLoadingBarNode extends Node {
    */
   private end(): void {
     this.loadingBarAnimation = null;
-    this.newChallenge();
+    this.newChallengeCallback();
   }
 }
 
diff --git a/js/game/view/SubitizeRevealButton.ts b/js/game/view/SubitizeRevealButton.ts
index 77ec03a8..2f973b4e 100644
--- a/js/game/view/SubitizeRevealButton.ts
+++ b/js/game/view/SubitizeRevealButton.ts
@@ -20,6 +20,7 @@ import NumberPlayColors from '../../common/NumberPlayColors.js';
 // constants
 const BUTTON_SIDE_LENGTH = SceneryPhetConstants.DEFAULT_BUTTON_RADIUS * 2;
 const BUTTON_CONTENT_MARGIN = 6;
+const BUTTON_TOUCH_AREA_DILATION = 10;
 
 class SubitizeRevealButton extends RectangularPushButton {
 
@@ -42,8 +43,8 @@ class SubitizeRevealButton extends RectangularPushButton {
       content: eyeNode,
       xMargin: BUTTON_CONTENT_MARGIN,
       yMargin: BUTTON_CONTENT_MARGIN,
-      touchAreaXDilation: 10,
-      touchAreaYDilation: 10,
+      touchAreaXDilation: BUTTON_TOUCH_AREA_DILATION,
+      touchAreaYDilation: BUTTON_TOUCH_AREA_DILATION,
       size: new Dimension2( BUTTON_SIDE_LENGTH, BUTTON_SIDE_LENGTH ),
       baseColor: NumberPlayColors.subitizeGameLightColorProperty,
       visibleProperty: revealButtonVisibleProperty,
diff --git a/js/game/view/SubitizerNode.ts b/js/game/view/SubitizerNode.ts
index dc8fecbf..1ec74d68 100644
--- a/js/game/view/SubitizerNode.ts
+++ b/js/game/view/SubitizerNode.ts
@@ -26,7 +26,7 @@ const REVEAL_BUTTON_MARGIN = 12;
 
 class SubitizerNode extends Node {
 
-  constructor( subitizer: Subitizer, isChallengeSolvedProperty: BooleanProperty, newChallenge: () => void ) {
+  constructor( subitizer: Subitizer, isChallengeSolvedProperty: BooleanProperty, newChallengeCallback: () => void ) {
     super();
 
     // for scaling the objects
@@ -43,7 +43,7 @@ class SubitizerNode extends Node {
     this.addChild( backgroundNode );
 
     // create and add the subitizeLoadingBarNode
-    const subitizeLoadingBarNode = new SubitizeLoadingBarNode( newChallenge, subitizer.isLoadingBarAnimatingProperty );
+    const subitizeLoadingBarNode = new SubitizeLoadingBarNode( newChallengeCallback, subitizer.isLoadingBarAnimatingProperty );
     subitizeLoadingBarNode.center = this.center;
     this.addChild( subitizeLoadingBarNode );
 
diff --git a/js/numberPlayStrings.ts b/js/numberPlayStrings.ts
index 673207cb..a67fd245 100644
--- a/js/numberPlayStrings.ts
+++ b/js/numberPlayStrings.ts
@@ -53,7 +53,8 @@ type StringsType = {
   'gameLevelPattern': string,
   'chooseYourGame': string,
   'counting': string,
-  'subitize': string
+  'subitize': string,
+  'plusOne': string
 };
 
 const numberPlayStrings = getStringModule( 'NUMBER_PLAY' ) as StringsType;
diff --git a/number-play-strings_en.json b/number-play-strings_en.json
index 8c054fcd..e9ad10e1 100644
--- a/number-play-strings_en.json
+++ b/number-play-strings_en.json
@@ -124,5 +124,8 @@
   },
   "subitize": {
     "value": "Subitize"
+  },
+  "plusOne": {
+    "value": "+1"
   }
 }
\ No newline at end of file