diff --git a/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scenes/GridWorld.unity b/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scenes/GridWorld.unity
index a026a6490b..60fca12cd5 100644
--- a/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scenes/GridWorld.unity
+++ b/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scenes/GridWorld.unity
@@ -13,7 +13,7 @@ OcclusionCullingSettings:
 --- !u!104 &2
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   m_ObjectHideFlags: 0
-  serializedVersion: 9
+  serializedVersion: 8
   m_Fog: 0
   m_FogColor: {r: 0.5, g: 0.5, b: 0.5, a: 1}
   m_FogMode: 3
@@ -38,8 +38,7 @@ RenderSettings:
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-  m_IndirectSpecularColor: {r: 0.43668893, g: 0.4842832, b: 0.56452656, a: 1}
-  m_UseRadianceAmbientProbe: 0
+  m_IndirectSpecularColor: {r: 0.43667555, g: 0.4842717, b: 0.56452394, a: 1}
 --- !u!157 &3
 LightmapSettings:
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@@ -55,10 +54,11 @@ LightmapSettings:
     m_EnableBakedLightmaps: 1
     m_EnableRealtimeLightmaps: 1
   m_LightmapEditorSettings:
-    serializedVersion: 10
+    serializedVersion: 9
     m_Resolution: 2
     m_BakeResolution: 40
-    m_AtlasSize: 1024
+    m_TextureWidth: 1024
+    m_TextureHeight: 1024
     m_AO: 0
     m_AOMaxDistance: 1
     m_CompAOExponent: 1
@@ -77,18 +77,15 @@ LightmapSettings:
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     m_PVRSampleCount: 500
     m_PVRBounces: 2
-    m_PVRFilterTypeDirect: 0
-    m_PVRFilterTypeIndirect: 0
-    m_PVRFilterTypeAO: 0
+    m_PVRFiltering: 0
     m_PVRFilteringMode: 1
     m_PVRCulling: 1
     m_PVRFilteringGaussRadiusDirect: 1
     m_PVRFilteringGaussRadiusIndirect: 5
     m_PVRFilteringGaussRadiusAO: 2
-    m_PVRFilteringAtrousPositionSigmaDirect: 0.5
-    m_PVRFilteringAtrousPositionSigmaIndirect: 2
-    m_PVRFilteringAtrousPositionSigmaAO: 1
-    m_ShowResolutionOverlay: 1
+    m_PVRFilteringAtrousColorSigma: 1
+    m_PVRFilteringAtrousNormalSigma: 1
+    m_PVRFilteringAtrousPositionSigma: 1
   m_LightingDataAsset: {fileID: 0}
   m_UseShadowmask: 0
 --- !u!196 &4
@@ -110,8 +107,6 @@ NavMeshSettings:
     manualTileSize: 0
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-    debug:
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   m_NavMeshData: {fileID: 0}
 --- !u!1 &2047662
 GameObject:
@@ -231,6 +226,20 @@ Light:
   m_Lightmapping: 4
   m_AreaSize: {x: 1, y: 1}
   m_BounceIntensity: 1
+  m_FalloffTable:
+    m_Table[0]: 0
+    m_Table[1]: 0
+    m_Table[2]: 0
+    m_Table[3]: 0
+    m_Table[4]: 0
+    m_Table[5]: 0
+    m_Table[6]: 0
+    m_Table[7]: 0
+    m_Table[8]: 0
+    m_Table[9]: 0
+    m_Table[10]: 0
+    m_Table[11]: 0
+    m_Table[12]: 0
   m_ColorTemperature: 6570
   m_UseColorTemperature: 0
   m_ShadowRadius: 0
@@ -311,11 +320,11 @@ Camera:
   m_TargetEye: 3
   m_HDR: 0
   m_AllowMSAA: 1
-  m_AllowDynamicResolution: 0
   m_ForceIntoRT: 0
   m_OcclusionCulling: 1
   m_StereoConvergence: 10
   m_StereoSeparation: 0.022
+  m_StereoMirrorMode: 0
 --- !u!4 &231883447
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@@ -423,6 +432,18 @@ RectTransform:
   m_AnchoredPosition: {x: 0, y: 0}
   m_SizeDelta: {x: 0, y: 0}
   m_Pivot: {x: 0, y: 0}
+--- !u!114 &382957182
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+  m_EditorClassIdentifier: 
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 --- !u!1 &486401523
 GameObject:
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@@ -516,11 +537,11 @@ Camera:
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   m_HDR: 0
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-  m_AllowDynamicResolution: 0
   m_ForceIntoRT: 0
   m_OcclusionCulling: 1
   m_StereoConvergence: 10
   m_StereoSeparation: 0.022
+  m_StereoMirrorMode: 0
 --- !u!1 &742849316
 GameObject:
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@@ -610,11 +631,9 @@ MeshRenderer:
   m_Enabled: 1
   m_CastShadows: 0
   m_ReceiveShadows: 1
-  m_DynamicOccludee: 1
   m_MotionVectors: 1
   m_LightProbeUsage: 1
   m_ReflectionProbeUsage: 1
-  m_RenderingLayerMask: 4294967295
   m_Materials:
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   m_StaticBatchInfo:
@@ -627,7 +646,6 @@ MeshRenderer:
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   m_IgnoreNormalsForChartDetection: 0
   m_ImportantGI: 0
-  m_StitchLightmapSeams: 0
   m_SelectedEditorRenderState: 3
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@@ -695,11 +713,9 @@ MeshRenderer:
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   m_ReceiveShadows: 1
-  m_DynamicOccludee: 1
   m_MotionVectors: 1
   m_LightProbeUsage: 1
   m_ReflectionProbeUsage: 1
-  m_RenderingLayerMask: 4294967295
   m_Materials:
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   m_StaticBatchInfo:
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-  m_StitchLightmapSeams: 0
   m_SelectedEditorRenderState: 3
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@@ -753,31 +768,6 @@ Transform:
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   m_RootOrder: 1
   m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
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-  m_EditorClassIdentifier: 
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 GameObject:
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@@ -805,11 +795,9 @@ MeshRenderer:
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   m_ReceiveShadows: 1
-  m_DynamicOccludee: 1
   m_MotionVectors: 1
   m_LightProbeUsage: 1
   m_ReflectionProbeUsage: 1
-  m_RenderingLayerMask: 4294967295
   m_Materials:
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@@ -822,7 +810,6 @@ MeshRenderer:
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   m_ImportantGI: 0
-  m_StitchLightmapSeams: 0
   m_SelectedEditorRenderState: 3
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   m_AutoUVMaxDistance: 0.5
@@ -840,9 +827,9 @@ MeshCollider:
   m_Material: {fileID: 0}
   m_IsTrigger: 0
   m_Enabled: 0
-  serializedVersion: 3
+  serializedVersion: 2
   m_Convex: 0
-  m_CookingOptions: 14
+  m_InflateMesh: 0
   m_SkinWidth: 0.01
   m_Mesh: {fileID: 10209, guid: 0000000000000000e000000000000000, type: 0}
 --- !u!33 &1208586860
@@ -920,11 +907,11 @@ MonoBehaviour:
     vectorActionSpaceType: 0
   brainType: 0
   CoreBrains:
-  - {fileID: 2068928320}
-  - {fileID: 1049818079}
-  - {fileID: 1176639739}
-  - {fileID: 0}
-  instanceID: 142728
+  - {fileID: 1836367505}
+  - {fileID: 1702244739}
+  - {fileID: 382957182}
+  - {fileID: 1802138297}
+  instanceID: 14072
 --- !u!1 &1553342942
 GameObject:
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@@ -999,6 +986,19 @@ CanvasRenderer:
   m_PrefabParentObject: {fileID: 0}
   m_PrefabInternal: {fileID: 0}
   m_GameObject: {fileID: 1553342942}
+--- !u!114 &1702244739
+MonoBehaviour:
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+  m_PrefabParentObject: {fileID: 0}
+  m_PrefabInternal: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 943466ab374444748a364f9d6c3e2fe2, type: 3}
+  m_Name: (Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)(Clone)
+  m_EditorClassIdentifier: 
+  broadcast: 1
+  brain: {fileID: 1535917239}
 --- !u!1 &1726089810
 GameObject:
   m_ObjectHideFlags: 0
@@ -1026,11 +1026,9 @@ MeshRenderer:
   m_Enabled: 1
   m_CastShadows: 0
   m_ReceiveShadows: 1
-  m_DynamicOccludee: 1
   m_MotionVectors: 1
   m_LightProbeUsage: 1
   m_ReflectionProbeUsage: 1
-  m_RenderingLayerMask: 4294967295
   m_Materials:
   - {fileID: 2100000, guid: 214660f4189b04cada2137381f5c3607, type: 2}
   m_StaticBatchInfo:
@@ -1043,7 +1041,6 @@ MeshRenderer:
   m_PreserveUVs: 1
   m_IgnoreNormalsForChartDetection: 0
   m_ImportantGI: 0
-  m_StitchLightmapSeams: 0
   m_SelectedEditorRenderState: 3
   m_MinimumChartSize: 4
   m_AutoUVMaxDistance: 0.5
@@ -1084,6 +1081,57 @@ Transform:
   m_Father: {fileID: 486401524}
   m_RootOrder: 4
   m_LocalEulerAnglesHint: {x: 0, y: 90, z: 0}
+--- !u!114 &1802138297
+MonoBehaviour:
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+  m_GameObject: {fileID: 0}
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+  m_Script: {fileID: 11500000, guid: 8b23992c8eb17439887f5e944bf04a40, type: 3}
+  m_Name: (Clone)
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+  graphScope: 
+  graphPlaceholders: []
+  BatchSizePlaceholderName: batch_size
+  VectorObservationPlacholderName: vector_observation
+  RecurrentInPlaceholderName: recurrent_in
+  RecurrentOutPlaceholderName: recurrent_out
+  VisualObservationPlaceholderName: []
+  ActionPlaceholderName: action
+  PreviousActionPlaceholderName: prev_action
+  brain: {fileID: 0}
+--- !u!114 &1836367505
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+  m_Script: {fileID: 11500000, guid: 41e9bda8f3cf1492fa74926a530f6f70, type: 3}
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+    branchIndex: 0
+    value: 4
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 --- !u!1 &1938864789
 GameObject:
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@@ -1111,11 +1159,9 @@ MeshRenderer:
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-  m_DynamicOccludee: 1
   m_MotionVectors: 1
   m_LightProbeUsage: 1
   m_ReflectionProbeUsage: 1
-  m_RenderingLayerMask: 4294967295
   m_Materials:
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   m_StaticBatchInfo:
@@ -1128,7 +1174,6 @@ MeshRenderer:
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   m_ImportantGI: 0
-  m_StitchLightmapSeams: 0
   m_SelectedEditorRenderState: 3
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   m_AutoUVMaxDistance: 0.5
@@ -1235,31 +1280,3 @@ GameObject:
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     type: 2}
   m_PrefabInternal: {fileID: 2008405821}
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diff --git a/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scripts/GridAgent.cs b/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scripts/GridAgent.cs
index 96186d597c..a1957f5310 100755
--- a/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scripts/GridAgent.cs
+++ b/MLAgentsSDK/Assets/ML-Agents/Examples/GridWorld/Scripts/GridAgent.cs
@@ -1,4 +1,5 @@
-using UnityEngine;
+using System;
+using UnityEngine;
 using System.Linq;
 using MLAgents;
 
@@ -9,6 +10,16 @@ public class GridAgent : Agent
     public float timeBetweenDecisionsAtInference;
     private float timeSinceDecision;
 
+    [Tooltip("Selecting will turn on action masking. Note that a model trained with action " +
+             "masking turned on may not behave optimally when action masking is turned off.")]
+    public bool maskActions = true;
+
+    private const int NoAction = 0;  // do nothing!
+    private const int Up = 1;
+    private const int Down = 2;
+    private const int Left = 3;
+    private const int Right = 4;
+
     public override void InitializeAgent()
     {
         academy = FindObjectOfType(typeof(GridAcademy)) as GridAcademy;
@@ -16,53 +27,90 @@ public override void InitializeAgent()
 
     public override void CollectObservations()
     {
+        // There are no numeric observations to collect as this environment uses visual
+        // observations.
 
+        // Mask the necessary actions if selected by the user.
+        if (maskActions)
+        {
+            SetMask();
+        }
     }
 
-    // to be implemented by the developer
-    public override void AgentAction(float[] vectorAction, string textAction)
+    /// <summary>
+    /// Applies the mask for the agents action to disallow unnecessary actions.
+    /// </summary>
+    private void SetMask()
     {
-        AddReward(-0.01f);
-        int action = Mathf.FloorToInt(vectorAction[0]);
+        // Prevents the agent from picking an action that would make it collide with a wall
+        var positionX = (int) transform.position.x;
+        var positionZ = (int) transform.position.z;
+        var maxPosition = academy.gridSize - 1;
 
-        // 0 - Forward, 1 - Backward, 2 - Left, 3 - Right
-        Vector3 targetPos = transform.position;
-        if (action == 4)
+        if (positionX == 0)
         {
-            targetPos = transform.position + new Vector3(1f, 0, 0f);
+            SetActionMask(Left);
         }
 
-        if (action == 3)
+        if (positionX == maxPosition)
         {
-            targetPos = transform.position + new Vector3(-1f, 0, 0f);
+            SetActionMask(Right);
         }
 
-        if (action == 1)
+        if (positionZ == 0)
         {
-            targetPos = transform.position + new Vector3(0f, 0, 1f);
+            SetActionMask(Down);
         }
 
-        if (action == 2)
+        if (positionZ == maxPosition)
         {
-            targetPos = transform.position + new Vector3(0f, 0, -1f);
+            SetActionMask(Up);
+        }
+    }
+
+    // to be implemented by the developer
+    public override void AgentAction(float[] vectorAction, string textAction)
+    {
+        AddReward(-0.01f);
+        int action = Mathf.FloorToInt(vectorAction[0]);
+
+        Vector3 targetPos = transform.position;
+        switch (action)
+        {
+            case NoAction:
+                // do nothing
+                break;
+            case Right:
+                targetPos = transform.position + new Vector3(1f, 0, 0f);
+                break;
+            case Left:
+                targetPos = transform.position + new Vector3(-1f, 0, 0f);
+                break;
+            case Up:
+                targetPos = transform.position + new Vector3(0f, 0, 1f);
+                break;
+            case Down:
+                targetPos = transform.position + new Vector3(0f, 0, -1f);
+                break;
+            default:
+                throw new ArgumentException("Invalid action value");
         }
 
         Collider[] blockTest = Physics.OverlapBox(targetPos, new Vector3(0.3f, 0.3f, 0.3f));
-        if (blockTest.Where(col => col.gameObject.tag == "wall").ToArray().Length == 0)
+        if (blockTest.Where(col => col.gameObject.CompareTag("wall")).ToArray().Length == 0)
         {
             transform.position = targetPos;
 
-            if (blockTest.Where(col => col.gameObject.tag == "goal").ToArray().Length == 1)
+            if (blockTest.Where(col => col.gameObject.CompareTag("goal")).ToArray().Length == 1)
             {
                 Done();
                 SetReward(1f);
             }
-            if (blockTest.Where(col => col.gameObject.tag == "pit").ToArray().Length == 1)
+            if (blockTest.Where(col => col.gameObject.CompareTag("pit")).ToArray().Length == 1)
             {
                 Done();
                 SetReward(-1f);
             }
-
         }
     }
 
diff --git a/docs/Learning-Environment-Examples.md b/docs/Learning-Environment-Examples.md
index db4695c77c..fcdc38df7d 100644
--- a/docs/Learning-Environment-Examples.md
+++ b/docs/Learning-Environment-Examples.md
@@ -75,7 +75,11 @@ If you would like to contribute environments, please see our
 * Brains: One brain with the following observation/action space.
   * Vector Observation space: None
   * Vector Action space: (Discrete) Size of 4, corresponding to movement in
-    cardinal directions.
+    cardinal directions. Note that for this environment, 
+    [action masking](Learning-Environment-Design-Agents.md#masking-discrete-actions)
+    is turned on by default (this option can be toggled
+    using the `Mask Actions` checkbox within the `trueAgent` GameObject).
+    The trained model file provided was generated with action masking turned on.
   * Visual Observations: One corresponding to top-down view of GridWorld.
 * Reset Parameters: Three, corresponding to grid size, number of obstacles, and
   number of goals.