diff --git a/.gitignore b/.gitignore
index c6675ea9..2e5fa548 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@ node_modules/
 *.sublime-project
 *.sublime-workspace
 .eslintcache
+package-lock.json
diff --git a/js/SceneryPhetFluent.ts b/js/SceneryPhetFluent.ts
index 12bd32a4..ead403a7 100644
--- a/js/SceneryPhetFluent.ts
+++ b/js/SceneryPhetFluent.ts
@@ -119,6 +119,7 @@ addToMapIfDefined( 'keyboardHelpDialog_faucetControls_openFaucetBriefly', 'keybo
 addToMapIfDefined( 'keyboardHelpDialog_timingControls_timingControls', 'keyboardHelpDialog.timingControls.timingControlsStringProperty' );
 addToMapIfDefined( 'keyboardHelpDialog_timingControls_pauseOrPlayAction', 'keyboardHelpDialog.timingControls.pauseOrPlayActionStringProperty' );
 addToMapIfDefined( 'speed_fast', 'speed.fastStringProperty' );
+addToMapIfDefined( 'speed_superSlow', 'speed.superSlowStringProperty' );
 addToMapIfDefined( 'symbol_ohms', 'symbol.ohmsStringProperty' );
 addToMapIfDefined( 'symbol_resistivity', 'symbol.resistivityStringProperty' );
 addToMapIfDefined( 'wavelength', 'wavelengthStringProperty' );
@@ -377,7 +378,8 @@ const SceneryPhetFluent = {
   speed: {
     normalStringProperty: new FluentConstant( fluentSupport.bundleProperty, 'speed_normal', _.get( SceneryPhetStrings, 'speed.normalStringProperty' ) ),
     slowStringProperty: new FluentConstant( fluentSupport.bundleProperty, 'speed_slow', _.get( SceneryPhetStrings, 'speed.slowStringProperty' ) ),
-    fastStringProperty: new FluentConstant( fluentSupport.bundleProperty, 'speed_fast', _.get( SceneryPhetStrings, 'speed.fastStringProperty' ) )
+    fastStringProperty: new FluentConstant( fluentSupport.bundleProperty, 'speed_fast', _.get( SceneryPhetStrings, 'speed.fastStringProperty' ) ),
+    superSlowStringProperty: new FluentConstant( fluentSupport.bundleProperty, 'speed_superSlow', _.get( SceneryPhetStrings, 'speed.superSlowStringProperty' ) )
   },
   symbol: {
     ohmsStringProperty: new FluentConstant( fluentSupport.bundleProperty, 'symbol_ohms', _.get( SceneryPhetStrings, 'symbol.ohmsStringProperty' ) ),
diff --git a/js/SceneryPhetStrings.ts b/js/SceneryPhetStrings.ts
index 14f9c82e..32d69750 100644
--- a/js/SceneryPhetStrings.ts
+++ b/js/SceneryPhetStrings.ts
@@ -137,6 +137,7 @@ type StringsType = {
     'normalStringProperty': LocalizedStringProperty;
     'slowStringProperty': LocalizedStringProperty;
     'fastStringProperty': LocalizedStringProperty;
+    'superSlowStringProperty': LocalizedStringProperty;
   };
   'symbol': {
     'ohmsStringProperty': LocalizedStringProperty;
diff --git a/js/TimeSpeed.ts b/js/TimeSpeed.ts
index 911a8d69..863f131f 100644
--- a/js/TimeSpeed.ts
+++ b/js/TimeSpeed.ts
@@ -16,6 +16,7 @@ export default class TimeSpeed extends EnumerationValue {
   public static readonly FAST = new TimeSpeed();
   public static readonly NORMAL = new TimeSpeed();
   public static readonly SLOW = new TimeSpeed();
+  public static readonly SUPER_SLOW = new TimeSpeed();
 
   // Gets a list of keys, values and mapping between them. For use in EnumerationProperty and PhET-iO
   public static readonly enumeration = new Enumeration( TimeSpeed );
diff --git a/js/TimeSpeedRadioButtonGroup.ts b/js/TimeSpeedRadioButtonGroup.ts
index b92e21d9..25b0a7ca 100644
--- a/js/TimeSpeedRadioButtonGroup.ts
+++ b/js/TimeSpeedRadioButtonGroup.ts
@@ -36,6 +36,10 @@ SPEED_LABEL_MAP.set( TimeSpeed.SLOW, {
   stringProperty: SceneryPhetStrings.speed.slowStringProperty,
   tandemName: 'slowRadioButton'
 } );
+SPEED_LABEL_MAP.set( TimeSpeed.SUPER_SLOW, {
+  stringProperty: SceneryPhetStrings.speed.superSlowStringProperty,
+  tandemName: 'superSlowRadioButton'
+} );
 
 type SelfOptions = {
   radius?: number;
diff --git a/js/demo/components/demoTimeControlNode.ts b/js/demo/components/demoTimeControlNode.ts
index 8baad9ea..dc4ad539 100644
--- a/js/demo/components/demoTimeControlNode.ts
+++ b/js/demo/components/demoTimeControlNode.ts
@@ -47,7 +47,7 @@ export default function demoTimeControlNode( layoutBounds: Bounds2 ): Node {
   // a TimeControlNode with swapped layout for radio buttons with radio buttons wrapped in a panel
   const customTimeControlNode = new TimeControlNode( new BooleanProperty( true ), {
     timeSpeedProperty: new EnumerationProperty( TimeSpeed.SLOW ),
-    timeSpeeds: [ TimeSpeed.NORMAL, TimeSpeed.FAST, TimeSpeed.SLOW ],
+    timeSpeeds: [ TimeSpeed.NORMAL, TimeSpeed.FAST, TimeSpeed.SLOW, TimeSpeed.SUPER_SLOW ],
     speedRadioButtonGroupPlacement: 'left',
     flowBoxSpacing: 40,
     enabledProperty: enabledProperty
diff --git a/scenery-phet-strings_en.json b/scenery-phet-strings_en.json
index 4c90e2ce..250a1a25 100644
--- a/scenery-phet-strings_en.json
+++ b/scenery-phet-strings_en.json
@@ -317,6 +317,9 @@
   "speed.fast": {
     "value": "Fast"
   },
+  "speed.superSlow": {
+    "value": "Super Slow"
+  },
   "symbol.ohms": {
     "value": "Ω"
   },
diff --git a/scenery-phet-strings_en.yaml b/scenery-phet-strings_en.yaml
index 55858dbc..7761992f 100644
--- a/scenery-phet-strings_en.yaml
+++ b/scenery-phet-strings_en.yaml
@@ -104,6 +104,7 @@ keyboardHelpDialog.faucetControls.openFaucetBriefly:    Open faucet briefly
 keyboardHelpDialog.timingControls.timingControls:       Time Controls
 keyboardHelpDialog.timingControls.pauseOrPlayAction:    Pause or play action
 speed.fast:                                             Fast
+speed.superSlow:                                        Super Slow
 symbol.ohms:                                            Ω
 symbol.resistivity:                                     ρ
 comboBoxDisplay.valueUnits:                             '{{value}} {{units}}'