diff --git a/src/engine/DynamicsWorld.h b/src/engine/DynamicsWorld.h
index 975bf661..e9e6bae6 100644
--- a/src/engine/DynamicsWorld.h
+++ b/src/engine/DynamicsWorld.h
@@ -373,7 +373,7 @@ inline Vector3 DynamicsWorld::getGravity() const {
 /**
  * @param gravity The gravity vector (in meter per seconds squared)
  */
-inline Vector3 DynamicsWorld::setGravity(Vector3& gravity) {
+inline void DynamicsWorld::setGravity(Vector3& gravity) {
     mGravity = gravity;
 }
 
diff --git a/testbed/src/Gui.cpp b/testbed/src/Gui.cpp
index 6d5ad0eb..7a1ac83f 100644
--- a/testbed/src/Gui.cpp
+++ b/testbed/src/Gui.cpp
@@ -107,6 +107,8 @@ void Gui::init() {
 
 void Gui::displayHeader() {
 
+    TestbedApplication& app = TestbedApplication::getInstance();
+
     ImVec2 buttonSize(120, 40);
 
     int display_w, display_h;
@@ -122,10 +124,23 @@ void Gui::displayHeader() {
 
         ImGui::Begin("Header", NULL, ImVec2(display_w, HEADER_HEIGHT), 1.0f, window_flags);
         ImGui::SetWindowPos(ImVec2(0, 0));
-        ImGui::Button("Play", buttonSize); ImGui::SameLine();
-        ImGui::Button("Pause", buttonSize); ImGui::SameLine();
-        ImGui::Button("Step", buttonSize); ImGui::SameLine();
-        ImGui::Button("Restart", buttonSize); ImGui::SameLine();
+
+        bool isRunning = app.mTimer.isRunning();
+        if (ImGui::Button(isRunning ? "Pause" : "Play", buttonSize)) {
+            app.togglePlayPauseSimulation();
+        }
+        ImGui::SameLine();
+
+        if (ImGui::Button("Step", buttonSize)) {
+            app.toggleTakeSinglePhysicsStep();
+        }
+        ImGui::SameLine();
+
+        if (ImGui::Button("Restart", buttonSize)) {
+            app.restartSimulation();
+        }
+        ImGui::SameLine();
+
         ImGui::End();
 
     ImGui::PopStyleColor(1);
@@ -152,8 +167,16 @@ void Gui::displayLeftPane() {
         ImGui::SetWindowPos(ImVec2(0, HEADER_HEIGHT));
 
         // ----- Left Pane Header ----- //
-        ImGui::Button("Scenes", buttonSize); ImGui::SameLine();
-        ImGui::Button("Physics", buttonSize); ImGui::SameLine();
+        if (ImGui::Button("Scenes", buttonSize)) {
+            mLeftPane = SCENES;
+        }
+        ImGui::SameLine();
+
+        if (ImGui::Button("Physics", buttonSize)) {
+            mLeftPane = PHYSICS;
+        }
+        ImGui::SameLine();
+
         ImGui::Button("Rendering", buttonSize); ImGui::SameLine();
         ImGui::Button("Profiling", buttonSize);
 
@@ -194,6 +217,11 @@ void Gui::displayScenesPane() {
 
 void Gui::displayPhysicsPane() {
 
+    TestbedApplication& app = TestbedApplication::getInstance();
+
+    // Physics time step
+    //float timestep = app.ge;
+    //ImGui::InputFloat("Timestep", &timestep, 0.01f, 1.0f);
 }
 
 void Gui::displayRenderingPane() {
@@ -241,10 +269,6 @@ void Gui::render() {
     //glfwPollEvents();
     beginNewFrame();
 
-    bool show_test_window = true;
-    bool show_another_window = false;
-    ImVec4 clear_color = ImColor(255, 255, 255);
-
     displayHeader();
     displayLeftPane();
 
diff --git a/testbed/src/Scene.h b/testbed/src/Scene.h
index 2f269a36..e6460805 100644
--- a/testbed/src/Scene.h
+++ b/testbed/src/Scene.h
@@ -35,8 +35,16 @@ struct EngineSettings {
 
     public:
 
-       float elapsedTime;       // Elapsed time (in seconds)
-       float timeStep;          // Current time step (in seconds)
+       float elapsedTime;                   // Elapsed time (in seconds)
+       float timeStep;                      // Current time step (in seconds)
+       int nbVelocitySolverIterations;      // Nb of velocity solver iterations
+       int nbPositionSolverIterations;      // Nb of position solver iterations
+       bool isSleepingEnabled;              // True if sleeping technique is enabled
+       float timeBeforeSleep;               // Time of inactivity before a body sleep
+       float sleepLinearVelocity;           // Sleep linear velocity
+       float sleepAngularVelocity;          // Sleep angular velocity
+       bool isGravityEnabled;               // True if gravity is enabled
+       openglframework::Vector3 gravity;    // Gravity vector
 
        /// Constructor
        EngineSettings() : elapsedTime(0.0f), timeStep(0.0f) {
diff --git a/testbed/src/TestbedApplication.cpp b/testbed/src/TestbedApplication.cpp
index cdc31397..d972aeb3 100644
--- a/testbed/src/TestbedApplication.cpp
+++ b/testbed/src/TestbedApplication.cpp
@@ -50,13 +50,15 @@ TestbedApplication& TestbedApplication::getInstance() {
 }
 
 // Constructor
-TestbedApplication::TestbedApplication() : mFPS(0), mNbFrames(0), mPreviousTime(0){
+TestbedApplication::TestbedApplication() : mFPS(0), mNbFrames(0), mPreviousTime(0) {
 
     mCurrentScene = NULL;
     mEngineSettings.timeStep = DEFAULT_TIMESTEP;
     mIsMultisamplingActive = true;
     mWidth = 1280;
     mHeight = 720;
+    mSinglePhysicsStepEnabled = false;
+    mSinglePhysicsStepDone = false;
 }
 
 // Destructor
@@ -175,6 +177,13 @@ void TestbedApplication::destroyScenes() {
     mCurrentScene = NULL;
 }
 
+void TestbedApplication::updateSinglePhysicsStep() {
+
+    assert(!mTimer.isRunning());
+
+    mCurrentScene->updatePhysics();
+}
+
 // Update the physics of the current scene
 void TestbedApplication::updatePhysics() {
 
@@ -202,7 +211,13 @@ void TestbedApplication::updatePhysics() {
 void TestbedApplication::update() {
 
     // Update the physics
-    updatePhysics();
+    if (mSinglePhysicsStepEnabled && !mSinglePhysicsStepDone) {
+        updateSinglePhysicsStep();
+        mSinglePhysicsStepDone = true;
+    }
+    else {
+        updatePhysics();
+    }
 
     // Compute the interpolation factor
     float factor = mTimer.computeInterpolationFactor(mEngineSettings.timeStep);
diff --git a/testbed/src/TestbedApplication.h b/testbed/src/TestbedApplication.h
index 9843653c..eb5d2276 100644
--- a/testbed/src/TestbedApplication.h
+++ b/testbed/src/TestbedApplication.h
@@ -81,6 +81,12 @@ class TestbedApplication {
         /// Width and height of the window
         int mWidth, mHeight;
 
+        /// True if the next simulation update is a single physics step
+        bool mSinglePhysicsStepEnabled;
+
+        /// True if the single physics step has been taken already
+        bool mSinglePhysicsStepDone;
+
         // -------------------- Methods -------------------- //
 
         /// Private constructor (for the singleton class)
@@ -98,6 +104,9 @@ class TestbedApplication {
         /// Update
         void update();
 
+        /// Update the simulation by taking a single physics step
+        void updateSinglePhysicsStep();
+
         /// Called when the windows is reshaped
         void reshape();
 
@@ -140,6 +149,15 @@ class TestbedApplication {
         /// Return the list of the scenes
         std::vector<Scene*> getScenes();
 
+        /// Start/stop the simulation
+        void togglePlayPauseSimulation();
+
+        /// Restart the simulation
+        void restartSimulation();
+
+        /// Set the variable to know if we need to take a single physics step
+        void toggleTakeSinglePhysicsStep();
+
     public :
 
         // -------------------- Methods -------------------- //
@@ -169,5 +187,31 @@ inline std::vector<Scene*> TestbedApplication::getScenes() {
     return mScenes;
 }
 
+// Start the simulation
+inline void TestbedApplication::togglePlayPauseSimulation() {
+
+    if (mTimer.isRunning()) {
+        mTimer.stop();
+    }
+    else {
+        mTimer.start();
+    }
+}
+
+// Restart the simulation
+inline void TestbedApplication::restartSimulation() {
+    mCurrentScene->reset();
+    mTimer.start();
+}
+
+// Take a single step of simulation
+inline void TestbedApplication::toggleTakeSinglePhysicsStep() {
+    mSinglePhysicsStepEnabled = true;
+    mSinglePhysicsStepDone = false;
+
+    if (mTimer.isRunning()) {
+        mSinglePhysicsStepEnabled = false;
+    }
+}
 
 #endif