diff --git a/destrum/include/destrum/App.h b/destrum/include/destrum/App.h
index 188b128..d1158f8 100644
--- a/destrum/include/destrum/App.h
+++ b/destrum/include/destrum/App.h
@@ -2,8 +2,12 @@
 #define APP_H
 #include <filesystem>
 #include <chrono>
+#include <memory>
+#include <optional>
 #include <string>
 
+#include <nlohmann/json.hpp>
+
 #include "glm/vec2.hpp"
 
 #include <SDL2/SDL.h>
@@ -17,6 +21,8 @@
 #include <destrum/Input/InputManager.h>
 
 
+class Scene;
+
 class App {
 public:
     struct AppParams {
@@ -28,6 +34,7 @@ public:
         bool showDebugUi{true};
         WindowMode windowMode{WindowMode::Windowed};
         bool startMaximized{false};
+        bool startInEditMode{false};
     };
 
     App();
@@ -45,7 +52,11 @@ public:
 
     virtual void onWindowResize(int, int) {};
 
-    // Called inside the "Windows" menu of the main menu bar, add toggles for the game's own windows here
+    virtual void onPlayModeChanged(bool) {}
+
+    [[nodiscard]] bool isPlaying() const { return playing; }
+    void requestPlayModeToggle() { playModeToggleRequested = true; }
+
     virtual void customWindowsMenu() {}
 
 protected:
@@ -92,6 +103,17 @@ protected:
     void drawWindowsMenu();
     void drawPhysicsPanel(float dt, float fixedDt, float accumulator);
 
+private:
+    void drawPlayControls();
+    void applyPlayModeToggle();
+    bool enterPlayMode();
+    void exitPlayMode();
+
+    bool playing{true};
+    bool playModeToggleRequested{false};
+    std::optional<nlohmann::json> editSnapshot;
+    std::weak_ptr<Scene> editScene;
+
 };
 
 
diff --git a/destrum/include/destrum/Scene/SceneManager.h b/destrum/include/destrum/Scene/SceneManager.h
index a81e56d..44340f9 100644
--- a/destrum/include/destrum/Scene/SceneManager.h
+++ b/destrum/include/destrum/Scene/SceneManager.h
@@ -18,6 +18,9 @@ public:
     Scene& GetCurrentScene() const;
     const std::vector<std::shared_ptr<Scene>>& GetActiveScenes() const { return m_activeScenes; }
 
+    void SetPlaying(bool playing) { m_playing = playing; }
+    [[nodiscard]] bool IsPlaying() const { return m_playing; }
+
     void Update(float dt);
     void FixedUpdate(float dt);
     void LateUpdate(float dt);
@@ -52,6 +55,7 @@ private:
 
     std::vector<std::shared_ptr<Scene>> m_activeScenes;
     std::vector<std::shared_ptr<Scene>> m_scenes;
+    bool m_playing{true};
 };
 
 #endif //SCENEMANAGER_H
diff --git a/destrum/include/destrum/Serialization/MaterialSerialization.h b/destrum/include/destrum/Serialization/MaterialSerialization.h
index 72dedbc..60be578 100644
--- a/destrum/include/destrum/Serialization/MaterialSerialization.h
+++ b/destrum/include/destrum/Serialization/MaterialSerialization.h
@@ -18,10 +18,8 @@ namespace MaterialSerialization {
 
     [[nodiscard]] std::optional<std::string> Validate(const nlohmann::json& materials);
 
-    // Materials that only exist at runtime (no source file) are stored in the scene or prefab
-    // file under their cache key, so the materialKeys in its objects resolve after a restart
     [[nodiscard]] nlohmann::json CollectEmbedded(const nlohmann::json& objects);
-    void RegisterEmbedded(const nlohmann::json& materials);
+    void RegisterEmbedded(const nlohmann::json& materials, bool overwriteExisting = false);
 }
 
 #endif //DESTRUM_MATERIALSERIALIZATION_H
diff --git a/destrum/include/destrum/Serialization/SceneSerializer.h b/destrum/include/destrum/Serialization/SceneSerializer.h
index dd583c3..8146aad 100644
--- a/destrum/include/destrum/Serialization/SceneSerializer.h
+++ b/destrum/include/destrum/Serialization/SceneSerializer.h
@@ -4,6 +4,7 @@
 #include <filesystem>
 #include <functional>
 #include <future>
+#include <optional>
 
 #include <nlohmann/json.hpp>
 
@@ -17,8 +18,11 @@ public:
         nlohmann::json root;
     };
 
+    [[nodiscard]] static std::optional<nlohmann::json> Capture(Scene& scene);
     static bool Save(Scene& scene, const std::filesystem::path& path);
 
+    static bool LoadFromJson(Scene& scene, const nlohmann::json& root);
+
     static bool Load(Scene& scene, const std::filesystem::path& path,
                      std::function<void(float)> progressCallback = nullptr);
 
@@ -27,8 +31,6 @@ public:
     static bool ConstructScene(Scene& scene, LoadResult& result,
                                std::function<void(float)> progressCallback = nullptr);
 
-    // Parse the scene file on a background thread. Call LoadFromJson on the
-    // main thread once the future is ready.
     static std::future<LoadResult> LoadSceneFileAsync(const std::filesystem::path& path);
 };
 
diff --git a/destrum/src/App.cpp b/destrum/src/App.cpp
index b297321..abb5365 100644
--- a/destrum/src/App.cpp
+++ b/destrum/src/App.cpp
@@ -7,7 +7,10 @@
 
 #include <destrum/FS/AssetFS.h>
 #include <destrum/Graphics/Resources/FontCache.h>
+#include <destrum/ObjectModel/GameObject.h>
+#include <destrum/Scene/Scene.h>
 #include <destrum/Scene/SceneManager.h>
+#include <destrum/Serialization/SceneSerializer.h>
 #include <destrum/Util/DeltaTime.h>
 
 #include "imgui.h"
@@ -67,6 +70,8 @@ void App::init(const AppParams& params)
 
         customInitStarted = true;
         customInit();
+        playing = !params.startInEditMode;
+        SceneManager::GetInstance().SetPlaying(playing);
         cleanedUp = false;
     } catch (...) {
         try {
@@ -179,6 +184,11 @@ if (!isRunning) break;
             continue;
         }
 
+        if (InputManager::GetInstance().WasKeyPressed(SDL_SCANCODE_F5))
+        {
+            playModeToggleRequested = true;
+        }
+
         // Consume SDL events before updating the base camera so held and
         // newly pressed inputs are applied in the same frame.
         camera.Update(dt);
@@ -239,6 +249,14 @@ if (!isRunning) break;
             imguiPass.endFrame();
         }
 
+        if (playModeToggleRequested)
+        {
+            ZoneScopedN("Play Mode Toggle");
+            playModeToggleRequested = false;
+            applyPlayModeToggle();
+            accumulator = 0.0f;
+        }
+
         {
             ZoneScopedN("FixedUpdate");
 
@@ -406,9 +424,111 @@ void App::drawWindowsMenu()
         ImGui::EndMenu();
     }
 
+    drawPlayControls();
+
     ImGui::EndMainMenuBar();
 }
 
+void App::drawPlayControls()
+{
+    const char* state = playing ? "PLAYING" : "EDIT";
+    const char* action = playing ? "Stop (F5)" : "Play (F5)";
+    const ImGuiStyle& style = ImGui::GetStyle();
+    const float width = ImGui::CalcTextSize(state).x + ImGui::CalcTextSize(action).x +
+                        style.ItemSpacing.x * 2.0f + style.FramePadding.x * 2.0f;
+
+    // Centered like Godot's run buttons, unless the menus already reach past the middle
+    ImGui::SetCursorPosX(std::max(ImGui::GetCursorPosX(), (ImGui::GetWindowWidth() - width) * 0.5f));
+    ImGui::TextColored(playing ? ImVec4{0.4f, 0.9f, 0.4f, 1.0f} : ImVec4{0.7f, 0.7f, 0.7f, 1.0f}, "%s", state);
+    if (ImGui::MenuItem(action))
+    {
+        playModeToggleRequested = true;
+    }
+}
+
+void App::applyPlayModeToggle()
+{
+    if (playing)
+    {
+        exitPlayMode();
+    }
+    else
+    {
+        enterPlayMode();
+    }
+}
+
+bool App::enterPlayMode()
+{
+    auto& sceneManager = SceneManager::GetInstance();
+    if (sceneManager.GetActiveScenes().empty())
+    {
+        spdlog::error("Cannot enter play mode without an active scene");
+        return false;
+    }
+
+    const std::shared_ptr<Scene> scene = sceneManager.GetActiveScenes().front();
+    auto snapshot = SceneSerializer::Capture(*scene);
+    if (!snapshot)
+    {
+        spdlog::error("Cannot enter play mode, scene \"{}\" could not be saved", scene->GetName());
+        return false;
+    }
+    if (const GameObject* selected = scene->GetSelectedObject())
+    {
+        (*snapshot)["selected"] = selected->GetId();
+    }
+
+    // Play runs the scene as it would load from disk, so nothing the editor did to the live objects
+    // (started components, unsaved runtime state) leaks into the game
+    if (!SceneSerializer::LoadFromJson(*scene, *snapshot))
+    {
+        spdlog::error("Cannot enter play mode, scene \"{}\" did not load back", scene->GetName());
+        return false;
+    }
+
+    editSnapshot = std::move(snapshot);
+    editScene = scene;
+    playing = true;
+    sceneManager.SetPlaying(true);
+    spdlog::info("Entered play mode");
+    onPlayModeChanged(true);
+    return true;
+}
+
+void App::exitPlayMode()
+{
+    auto& sceneManager = SceneManager::GetInstance();
+    playing = false;
+    sceneManager.SetPlaying(false);
+    InputManager::GetInstance().SetMouseCaptured(false);
+
+    const std::shared_ptr<Scene> scene = editScene.lock();
+    if (scene && editSnapshot)
+    {
+        const auto& scenes = sceneManager.GetScenes();
+        const auto it = std::find(scenes.begin(), scenes.end(), scene);
+        if (it != scenes.end() && (sceneManager.GetActiveScenes().empty() ||
+                                   sceneManager.GetActiveScenes().front() != scene))
+        {
+            sceneManager.SwitchScene(static_cast<int>(std::distance(scenes.begin(), it)));
+        }
+        if (!SceneSerializer::LoadFromJson(*scene, *editSnapshot))
+        {
+            spdlog::error("Could not restore scene \"{}\" to its state before play mode", scene->GetName());
+        }
+    }
+    else
+    {
+        spdlog::warn("The scene play mode started from no longer exists, nothing to restore");
+    }
+
+    editSnapshot.reset();
+    editScene.reset();
+    spdlog::info("Exited play mode");
+    onPlayModeChanged(false);
+}
+
 void App::drawPhysicsPanel(float dt, float fixedDt, float accumulator)
 {
     if (!ImGui::Begin("Physics", &m_DebugWindows.physics))
diff --git a/destrum/src/Scene/SceneManager.cpp b/destrum/src/Scene/SceneManager.cpp
index 8d7d48d..1940167 100644
--- a/destrum/src/Scene/SceneManager.cpp
+++ b/destrum/src/Scene/SceneManager.cpp
@@ -16,17 +16,27 @@ Scene& SceneManager::GetCurrentScene() const {
 
 void SceneManager::Update(float dt) {
     for (const auto& scene : m_activeScenes) {
-        scene->Update(dt);
+        if (m_playing) {
+            scene->Update(dt);
+        } else {
+            scene->CommitPendingAdditions();
+        }
     }
 }
 
 void SceneManager::FixedUpdate(float dt) {
+    if (!m_playing) {
+        return;
+    }
     for (const auto& scene : m_activeScenes) {
         scene->FixedUpdate(dt);
     }
 }
 
 void SceneManager::LateUpdate(float dt) {
+    if (!m_playing) {
+        return;
+    }
     for (const auto& scene : m_activeScenes) {
         scene->LateUpdate(dt);
     }
diff --git a/destrum/src/Serialization/MaterialSerialization.cpp b/destrum/src/Serialization/MaterialSerialization.cpp
index 3079209..399e699 100644
--- a/destrum/src/Serialization/MaterialSerialization.cpp
+++ b/destrum/src/Serialization/MaterialSerialization.cpp
@@ -173,7 +173,7 @@ namespace MaterialSerialization {
         return materials;
     }
 
-    void RegisterEmbedded(const json& materials) {
+    void RegisterEmbedded(const json& materials, bool overwriteExisting) {
         RenderResources* resources = GetResources();
         if (resources == nullptr || !materials.is_object()) {
             return;
@@ -197,12 +197,14 @@ namespace MaterialSerialization {
             }
         };
 
-        // A key that is already cached wins, so duplicating objects keeps sharing their material
         for (auto it = materials.begin(); it != materials.end(); ++it) {
-            if (resources->materials().findMaterialByKey(it.key())) {
-                continue;
+            const auto existing = resources->materials().findMaterialByKey(it.key());
+            if (!existing) {
+                resources->materials().addMaterial(FromJson(it.value(), readTexture), it.key());
+            } else if (overwriteExisting) {
+                resources->materials().getMaterialMutable(*existing) = FromJson(it.value(), readTexture);
+                GameState::GetInstance().Renderer().updateMaterialGPU(*existing);
             }
-            resources->materials().addMaterial(FromJson(it.value(), readTexture), it.key());
         }
     }
 }
diff --git a/destrum/src/Serialization/SceneSerializer.cpp b/destrum/src/Serialization/SceneSerializer.cpp
index b0315f7..c1cdb10 100644
--- a/destrum/src/Serialization/SceneSerializer.cpp
+++ b/destrum/src/Serialization/SceneSerializer.cpp
@@ -50,6 +50,10 @@ namespace {
             return "\"currentCamera\" must be an object id";
         }
 
+        if (root.contains("selected") && !root.at("selected").is_number_unsigned()) {
+            return "\"selected\" must be an object id";
+        }
+
         if (root.contains("materials")) {
             if (auto error = MaterialSerialization::Validate(root.at("materials"))) {
                 return error;
@@ -60,10 +64,10 @@ namespace {
     }
 }
 
-bool SceneSerializer::Save(Scene& scene, const std::filesystem::path& path) {
+std::optional<json> SceneSerializer::Capture(Scene& scene) {
     if (scene.IsIterating()) {
         spdlog::error("Cannot save a scene during an update or render phase: {}", scene.GetName());
-        return false;
+        return std::nullopt;
     }
 
     RegisterEngineComponents();
@@ -71,7 +75,7 @@ bool SceneSerializer::Save(Scene& scene, const std::filesystem::path& path) {
         scene.CommitPendingAdditions();
     } catch (const std::exception& exception) {
         spdlog::error("Failed to commit scene additions before save: {}", exception.what());
-        return false;
+        return std::nullopt;
     }
 
     json root;
@@ -106,23 +110,31 @@ bool SceneSerializer::Save(Scene& scene, const std::filesystem::path& path) {
         }
     } catch (const std::exception& exception) {
         spdlog::error("Cannot save scene \"{}\": {}", scene.GetName(), exception.what());
-        return false;
+        return std::nullopt;
     }
 
     if (auto bad = ObjectSerialization::FindNonFinite(root, "scene")) {
         spdlog::error("Cannot save scene \"{}\": {} is NaN or Inf", scene.GetName(), *bad);
-        return false;
+        return std::nullopt;
     }
 
     // Refuse to write anything Load would reject
     if (auto error = ValidateSceneJson(root)) {
         spdlog::error("Cannot save scene \"{}\", it would not load back: {}", scene.GetName(), *error);
+        return std::nullopt;
+    }
+    return root;
+}
+
+bool SceneSerializer::Save(Scene& scene, const std::filesystem::path& path) {
+    const auto root = Capture(scene);
+    if (!root) {
         return false;
     }
 
     std::string contents;
     try {
-        contents = root.dump(4);
+        contents = root->dump(4);
     } catch (const std::exception& exception) {
         spdlog::error("Failed to encode scene \"{}\": {}", scene.GetName(), exception.what());
         return false;
@@ -195,7 +207,7 @@ bool SceneSerializer::ConstructScene(Scene& scene, LoadResult& result,
     try {
         if (root.contains("materials")) {
             context = "materials";
-            MaterialSerialization::RegisterEmbedded(root.at("materials"));
+            MaterialSerialization::RegisterEmbedded(root.at("materials"), true);
             context = "scene";
         }
         idMap = ObjectSerialization::BuildObjects(stagingScene, root.at("objects")).idMap;
@@ -247,6 +259,11 @@ bool SceneSerializer::ConstructScene(Scene& scene, LoadResult& result,
         scene.m_name = root.at("name").get<std::string>();
     }
     scene.m_SelectedObjectId = InvalidObjectId;
+    if (const ObjectId selectedFileId = root.value("selected", InvalidObjectId); selectedFileId != InvalidObjectId) {
+        if (const auto it = idMap.find(selectedFileId); it != idMap.end()) {
+            scene.m_SelectedObjectId = it->second->GetId();
+        }
+    }
     scene.m_CurrentCameraId = InvalidObjectId;
     if (const ObjectId cameraFileId = root.value("currentCamera", InvalidObjectId); cameraFileId != InvalidObjectId) {
         if (const auto it = idMap.find(cameraFileId); it != idMap.end()) {
@@ -313,6 +330,18 @@ bool SceneSerializer::Load(Scene& scene, const std::filesystem::path& path,
     return ConstructScene(scene, result, std::move(progressCallback));
 }
 
+bool SceneSerializer::LoadFromJson(Scene& scene, const json& root) {
+    RegisterEngineComponents();
+    LoadResult result;
+    if (auto error = ValidateSceneJson(root)) {
+        spdlog::error("Invalid scene data for \"{}\": {}", scene.GetName(), *error);
+        return false;
+    }
+    result.root = root;
+    result.success = true;
+    return ConstructScene(scene, result);
+}
+
 std::future<SceneSerializer::LoadResult> SceneSerializer::LoadSceneFileAsync(
     const std::filesystem::path& path) {
     return std::async(std::launch::async, [path]() {
diff --git a/lightkeeper/include/Lightkeeper.h b/lightkeeper/include/Lightkeeper.h
index f48c2a1..b6167bb 100644
--- a/lightkeeper/include/Lightkeeper.h
+++ b/lightkeeper/include/Lightkeeper.h
@@ -1,6 +1,7 @@
 #ifndef LIGHTKEEPER_H
 #define LIGHTKEEPER_H
 
+#include <optional>
 #include <string>
 
 #include <destrum/App.h>
@@ -28,6 +29,7 @@ public:
 
     void onWindowResize(int newWidth, int newHeight) override;
     void customWindowsMenu() override;
+    void onPlayModeChanged(bool nowPlaying) override;
 
 private:
     void setupSkybox();
@@ -53,6 +55,7 @@ private:
     void submitColliderDebugLines();
 
     Camera camera{glm::vec3(0.f, 0.f, -5.f), glm::vec3(0, 1, 0)};
+    std::optional<Camera> editorCamera;
 
     std::unique_ptr<CubeMap> skyboxCubemap;
     MainSceneObjects mainScene{};
diff --git a/lightkeeper/src/Lightkeeper.cpp b/lightkeeper/src/Lightkeeper.cpp
index d8f5d60..e6c6e94 100644
--- a/lightkeeper/src/Lightkeeper.cpp
+++ b/lightkeeper/src/Lightkeeper.cpp
@@ -83,7 +83,7 @@ void LightKeeper::updateViewMode()
     auto& input = InputManager::GetInstance();
     FirstPersonController* player = mainScene.playerController;
 
-    if (player != nullptr && input.WasKeyPressed(SDL_SCANCODE_F5))
+    if (isPlaying() && player != nullptr && input.WasKeyPressed(SDL_SCANCODE_F6))
     {
         player->SetPossessed(!player->IsPossessed());
     }
@@ -100,13 +100,13 @@ void LightKeeper::updateViewMode()
 
 bool LightKeeper::isPlayerViewActive() const
 {
-    return mainScene.playerController != nullptr && mainScene.playerController->IsPossessed();
+    return isPlaying() && mainScene.playerController != nullptr && mainScene.playerController->IsPossessed();
 }
 
 CameraComponent* LightKeeper::getSceneCamera() const
 {
     const auto& activeScenes = SceneManager::GetInstance().GetActiveScenes();
-    if (useFreeCamera || activeScenes.empty()) {
+    if (!isPlaying() || useFreeCamera || activeScenes.empty()) {
         return nullptr;
     }
     return activeScenes.front()->GetCurrentCamera();
@@ -187,6 +187,23 @@ void LightKeeper::customFixedUpdate(float dt)
     SceneManager::GetInstance().FixedUpdate(dt);
 }
 
+void LightKeeper::onPlayModeChanged(bool nowPlaying)
+{
+    findPlayer();
+    if (nowPlaying) {
+        // The player view moves the free camera, put it back where the editor left it on Stop
+        editorCamera = camera;
+        if (mainScene.playerController != nullptr) {
+            mainScene.playerController->SetPossessed(true);
+        }
+    } else if (editorCamera) {
+        const float aspectRatio = camera.GetAspectRatio();
+        camera = *editorCamera;
+        camera.setAspectRatio(aspectRatio);
+        editorCamera.reset();
+    }
+}
+
 void LightKeeper::onWindowResize(int newWidth, int newHeight)
 {
     renderer.resize(gfxDevice, glm::ivec2{newWidth, newHeight});
diff --git a/lightkeeper/src/main.cpp b/lightkeeper/src/main.cpp
index 5703bd7..23c55e7 100644
--- a/lightkeeper/src/main.cpp
+++ b/lightkeeper/src/main.cpp
@@ -28,6 +28,7 @@ int main(int argc, char* argv[]) {
             .appName = "Destrum Engine",
             .windowTitle = "Lightkeeper",
             .exeDir = exeDir,
+            .startInEditMode = true,
         });
         app.run();
         app.cleanup();
diff --git a/tests/core_tests.cpp b/tests/core_tests.cpp
index 4dc9da7..6d99721 100644
--- a/tests/core_tests.cpp
+++ b/tests/core_tests.cpp
@@ -37,6 +37,20 @@ namespace {
         std::string GetTypeName() const override { return "TestComponent"; }
     };
 
+    class CountingComponent final : public Component {
+    public:
+        explicit CountingComponent(GameObject& owner) : Component(owner, "CountingComponent") {}
+
+        void Update(float) override { ++updates; }
+        void LateUpdate(float) override { ++lateUpdates; }
+        void FixedUpdate(float) override { ++fixedUpdates; }
+        std::string GetTypeName() const override { return "CountingComponent"; }
+
+        int updates{0};
+        int lateUpdates{0};
+        int fixedUpdates{0};
+    };
+
     class RemovingListener final : public EventListener {
     public:
         explicit RemovingListener(std::unique_ptr<RemovingListener>* victim)
@@ -268,6 +282,30 @@ namespace {
 
         SceneManager::GetInstance().Destroy();
     }
+
+    void testEditModeSkipsUpdates()
+    {
+        SceneManager& sceneManager = SceneManager::GetInstance();
+        Scene& scene = sceneManager.CreateScene("edit mode");
+        auto* counter = scene.CreateGameObject("counter")->AddComponent<CountingComponent>();
+
+        sceneManager.SetPlaying(false);
+        sceneManager.Update(0.1f);
+        sceneManager.FixedUpdate(0.1f);
+        sceneManager.LateUpdate(0.1f);
+        check(counter->updates == 0 && counter->fixedUpdates == 0 && counter->lateUpdates == 0,
+              "edit mode must not tick components");
+        check(scene.GetObjects().size() == 1, "edit mode must still add objects created in the editor");
+
+        sceneManager.SetPlaying(true);
+        sceneManager.Update(0.1f);
+        sceneManager.FixedUpdate(0.1f);
+        sceneManager.LateUpdate(0.1f);
+        check(counter->updates == 1 && counter->fixedUpdates == 1 && counter->lateUpdates == 1,
+              "play mode must tick components");
+
+        sceneManager.Destroy();
+    }
 }
 
 void RunCoreTests()
@@ -280,4 +318,5 @@ void RunCoreTests()
     testEngineComponentRegistration();
     testSceneCurrentCamera();
     testHierarchyMoves();
+    testEditModeSkipsUpdates();
 }
diff --git a/tests/serialization_tests.cpp b/tests/serialization_tests.cpp
index c9417af..7dc07b7 100644
--- a/tests/serialization_tests.cpp
+++ b/tests/serialization_tests.cpp
@@ -334,6 +334,40 @@ namespace {
 
         SceneManager::GetInstance().Destroy();
     }
+
+    void testPlayModeSnapshotRestore()
+    {
+        Scene& scene = SceneManager::GetInstance().CreateScene("snapshot");
+        GameObject* box = scene.CreateGameObject("box");
+        box->GetTransform().SetLocalPosition({1.f, 2.f, 3.f});
+        scene.CreateGameObject("other");
+        scene.CommitPendingAdditions();
+        scene.SetSelectedObject(box->GetId());
+
+        auto snapshot = SceneSerializer::Capture(scene);
+        check(snapshot.has_value(), "a scene must be capturable without a file");
+        (*snapshot)["selected"] = box->GetId();
+
+        // What play mode does to the scene before Stop restores it
+        box->GetTransform().SetLocalPosition({9.f, 9.f, 9.f});
+        scene.CreateGameObject("spawned during play");
+        scene.CommitPendingAdditions();
+
+        check(SceneSerializer::LoadFromJson(scene, *snapshot), "restoring a snapshot must succeed");
+        scene.CommitPendingAdditions();
+        check(scene.GetObjects().size() == 2 && findByName(scene, "spawned during play") == nullptr,
+              "restoring must drop objects created after the snapshot");
+        const GameObject* restored = findByName(scene, "box");
+        check(restored != nullptr && close(restored->GetTransform().GetLocalPosition().x, 1.f),
+              "restoring must bring back the captured transforms");
+        check(scene.GetSelectedObject() == restored, "the selection must follow the restored object");
+
+        check(!SceneSerializer::LoadFromJson(scene, nlohmann::json{{"objects", 5}}),
+              "an invalid snapshot must be rejected");
+        check(scene.GetObjects().size() == 2, "a rejected snapshot must leave the scene alone");
+
+        SceneManager::GetInstance().Destroy();
+    }
 }
 
 void RunSerializationTests()
@@ -350,4 +384,5 @@ void RunSerializationTests()
     testSceneFileIdsAreLocal();
     testMaterialJsonRoundTrip();
     testSceneValidatesEmbeddedMaterials();
+    testPlayModeSnapshotRestore();
 }