diff --git a/dev/tests/example.lua b/dev/tests/example.lua
index f030222d..e69de29b 100644
--- a/dev/tests/example.lua
+++ b/dev/tests/example.lua
@@ -1,3 +0,0 @@
-print("Hello from the example test!")
-test.sleep(1)
-print("2")
diff --git a/src/Mainloop.cpp b/src/Mainloop.cpp
new file mode 100644
index 00000000..180e75f5
--- /dev/null
+++ b/src/Mainloop.cpp
@@ -0,0 +1,30 @@
+#include "Mainloop.hpp"
+
+#include "debug/Logger.hpp"
+#include "engine.hpp"
+#include "frontend/screens/MenuScreen.hpp"
+#include "window/Window.hpp"
+
+static debug::Logger logger("mainloop");
+
+Mainloop::Mainloop(Engine& engine) : engine(engine) {
+}
+
+void Mainloop::run() {
+    auto& time = engine.getTime();
+
+    logger.info() << "starting menu screen";
+    engine.setScreen(std::make_shared<MenuScreen>(&engine));
+    
+    logger.info() << "main loop started";
+    while (!Window::isShouldClose()){
+        time.update(Window::time());
+        engine.updateFrontend();
+        if (!Window::isIconified()) {
+            engine.renderFrame();
+        }
+        engine.postUpdate();
+        engine.nextFrame();
+    }
+    logger.info() << "main loop stopped";
+}
diff --git a/src/Mainloop.hpp b/src/Mainloop.hpp
new file mode 100644
index 00000000..3cd2f608
--- /dev/null
+++ b/src/Mainloop.hpp
@@ -0,0 +1,11 @@
+#pragma once
+
+class Engine;
+
+class Mainloop {
+    Engine& engine;
+public:
+    Mainloop(Engine& engine);
+
+    void run();
+};
diff --git a/src/TestMainloop.cpp b/src/TestMainloop.cpp
new file mode 100644
index 00000000..617a65cd
--- /dev/null
+++ b/src/TestMainloop.cpp
@@ -0,0 +1,31 @@
+#include "TestMainloop.hpp"
+
+#include "logic/scripting/scripting.hpp"
+#include "interfaces/Process.hpp"
+#include "debug/Logger.hpp"
+#include "engine.hpp"
+
+static debug::Logger logger("mainloop");
+
+inline constexpr int TPS = 20;
+
+TestMainloop::TestMainloop(Engine& engine) : engine(engine) {
+}
+
+void TestMainloop::run() {
+    const auto& coreParams = engine.getCoreParameters();
+    auto& time = engine.getTime();
+
+    if (coreParams.testFile.empty()) {
+        logger.info() << "nothing to do";
+        return;
+    }
+
+    logger.info() << "starting test " << coreParams.testFile;
+    auto process = scripting::start_coroutine(coreParams.testFile);
+    while (process->isActive()) {
+        time.step(1.0f / static_cast<float>(TPS));
+        process->update();
+    }
+    logger.info() << "test finished";
+}
diff --git a/src/TestMainloop.hpp b/src/TestMainloop.hpp
new file mode 100644
index 00000000..b0acc9a7
--- /dev/null
+++ b/src/TestMainloop.hpp
@@ -0,0 +1,11 @@
+#pragma once
+
+class Engine;
+
+class TestMainloop {
+    Engine& engine;
+public:
+    TestMainloop(Engine& engine);
+
+    void run();
+};
diff --git a/src/Time.hpp b/src/Time.hpp
new file mode 100644
index 00000000..57fb5c22
--- /dev/null
+++ b/src/Time.hpp
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <stdint.h>
+
+class Time {
+    uint64_t frame = 0;
+    double lastTime = 0.0;
+    double delta = 0.0;
+public:
+    Time() {}
+
+    void update(double currentTime) {
+        frame++;
+        delta = currentTime - lastTime;
+        lastTime = currentTime;
+    }
+
+    void step(double delta) {
+        frame++;
+        lastTime += delta;
+    }
+
+    void set(double currentTime) {
+        lastTime = currentTime;
+    }
+
+    double getDelta() const {
+        return delta;
+    }
+
+    double getTime() const {
+        return lastTime;
+    }
+};
diff --git a/src/content/ContentPack.cpp b/src/content/ContentPack.cpp
index 9ed192b5..72d4540f 100644
--- a/src/content/ContentPack.cpp
+++ b/src/content/ContentPack.cpp
@@ -146,9 +146,7 @@ void ContentPack::scanFolder(
 std::vector<std::string> ContentPack::worldPacksList(const fs::path& folder) {
     fs::path listfile = folder / fs::path("packs.list");
     if (!fs::is_regular_file(listfile)) {
-        std::cerr << "warning: packs.list not found (will be created)";
-        std::cerr << std::endl;
-        files::write_string(listfile, "# autogenerated, do not modify\nbase\n");
+        throw std::runtime_error("missing file 'packs.list'");
     }
     return files::read_list(listfile);
 }
diff --git a/src/engine.cpp b/src/engine.cpp
index 8f970892..622a2fdb 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -20,7 +20,6 @@
 #include "frontend/screens/Screen.hpp"
 #include "frontend/screens/MenuScreen.hpp"
 #include "graphics/render/ModelsGenerator.hpp"
-#include "graphics/core/Batch2D.hpp"
 #include "graphics/core/DrawContext.hpp"
 #include "graphics/core/ImageData.hpp"
 #include "graphics/core/Shader.hpp"
@@ -36,7 +35,8 @@
 #include "window/Events.hpp"
 #include "window/input.hpp"
 #include "window/Window.hpp"
-#include "interfaces/Process.hpp"
+#include "Mainloop.hpp"
+#include "TestMainloop.hpp"
 
 #include <iostream>
 #include <assert.h>
@@ -92,6 +92,7 @@ Engine::Engine(CoreParameters coreParameters)
         if (Window::initialize(&settings.display)){
             throw initialize_error("could not initialize window");
         }
+        time.set(Window::time());
         if (auto icon = load_icon(resdir)) {
             icon->flipY();
             Window::setIcon(icon.get());
@@ -153,13 +154,6 @@ void Engine::onAssetsLoaded() {
     gui->onAssetsLoad(assets.get());
 }
 
-void Engine::updateTimers() {
-    frame++;
-    double currentTime = Window::time();
-    delta = currentTime - lastTime;
-    lastTime = currentTime;
-}
-
 void Engine::updateHotkeys() {
     if (Events::jpressed(keycode::F2)) {
         saveScreenshot();
@@ -179,70 +173,40 @@ void Engine::saveScreenshot() {
 
 void Engine::run() {
     if (params.headless) {
-        runTest();
+        TestMainloop(*this).run();
     } else {
-        mainloop();
+        Mainloop(*this).run();
     }
 }
 
-void Engine::runTest() {
-    if (params.testFile.empty()) {
-        logger.info() << "nothing to do";
-        return;
-    }
-    int tps = 20;
-
-    logger.info() << "starting test " << params.testFile;
-    auto process = scripting::start_coroutine(params.testFile);
-    while (process->isActive()) {
-        frame++;
-        delta = 1.0f / static_cast<float>(tps);
-        lastTime += delta;
-
-        process->update();
-    }
-    logger.info() << "test finished";
+void Engine::postUpdate() {
+    network->update();
+    processPostRunnables();
 }
 
-void Engine::mainloop() {
-    logger.info() << "starting menu screen";
-    setScreen(std::make_shared<MenuScreen>(this));
-
-    Batch2D batch(1024);
-    lastTime = Window::time();
-    
-    logger.info() << "engine started";
-    while (!Window::isShouldClose()){
-        assert(screen != nullptr);
-        updateTimers();
-        updateHotkeys();
-        audio::update(delta);
-
-        gui->act(delta, Viewport(Window::width, Window::height));
-        screen->update(delta);
-
-        if (!Window::isIconified()) {
-            renderFrame(batch);
-        }
-        Window::setFramerate(
-            Window::isIconified() && settings.display.limitFpsIconified.get()
-                ? 20
-                : settings.display.framerate.get()
-        );
-
-        network->update();
-        processPostRunnables();
-
-        Window::swapBuffers();
-        Events::pollEvents();
-    }
+void Engine::updateFrontend() {
+    double delta = time.getDelta();
+    updateHotkeys();
+    audio::update(delta);
+    gui->act(delta, Viewport(Window::width, Window::height));
+    screen->update(delta);
 }
 
-void Engine::renderFrame(Batch2D& batch) {
-    screen->draw(delta);
+void Engine::nextFrame() {
+    Window::setFramerate(
+        Window::isIconified() && settings.display.limitFpsIconified.get()
+            ? 20
+            : settings.display.framerate.get()
+    );
+    Window::swapBuffers();
+    Events::pollEvents();
+}
+
+void Engine::renderFrame() {
+    screen->draw(time.getDelta());
 
     Viewport viewport(Window::width, Window::height);
-    DrawContext ctx(nullptr, viewport, &batch);
+    DrawContext ctx(nullptr, viewport, nullptr);
     gui->draw(ctx, *assets);
 }
 
@@ -333,32 +297,31 @@ void Engine::loadAssets() {
         }
     }
     assets = std::move(new_assets);
-    
-    if (content) {
-        for (auto& [name, def] : content->blocks.getDefs()) {
-            if (def->model == BlockModel::custom) {
-                if (def->modelName.empty()) {
-                    assets->store(
-                        std::make_unique<model::Model>(
-                            ModelsGenerator::loadCustomBlockModel(
-                                def->customModelRaw, *assets, !def->shadeless
-                            )
-                        ),
-                        name + ".model"
-                    );
-                    def->modelName = def->name + ".model";
-                }
-            }
-        }
-        for (auto& [name, def] : content->items.getDefs()) {
+
+    if (content == nullptr) {
+        return;
+    }
+    for (auto& [name, def] : content->blocks.getDefs()) {
+        if (def->model == BlockModel::custom && def->modelName.empty()) {
             assets->store(
                 std::make_unique<model::Model>(
-                    ModelsGenerator::generate(*def, *content, *assets)
+                    ModelsGenerator::loadCustomBlockModel(
+                        def->customModelRaw, *assets, !def->shadeless
+                    )
                 ),
                 name + ".model"
             );
+            def->modelName = def->name + ".model";
         }
     }
+    for (auto& [name, def] : content->items.getDefs()) {
+        assets->store(
+            std::make_unique<model::Model>(
+                ModelsGenerator::generate(*def, *content, *assets)
+            ),
+            name + ".model"
+        );
+    }
 }
 
 static void load_configs(const fs::path& root) {
@@ -468,14 +431,6 @@ void Engine::loadAllPacks() {
     contentPacks = manager.getAll(manager.assembly(allnames));
 }
 
-double Engine::getDelta() const {
-    return delta;
-}
-
-double Engine::getUptime() const {
-    return lastTime;
-}
-
 void Engine::setScreen(std::shared_ptr<Screen> screen) {
     // reset audio channels (stop all sources)
     audio::reset_channel(audio::get_channel_index("regular"));
@@ -545,6 +500,14 @@ network::Network& Engine::getNetwork() {
     return *network;
 }
 
+Time& Engine::getTime() {
+    return time;
+}
+
 const CoreParameters& Engine::getCoreParameters() const {
     return params;
 }
+
+bool Engine::isHeadless() const {
+    return params.headless;
+}
diff --git a/src/engine.hpp b/src/engine.hpp
index a0d4a8e9..fee92e81 100644
--- a/src/engine.hpp
+++ b/src/engine.hpp
@@ -11,6 +11,7 @@
 #include "files/engine_paths.hpp"
 #include "files/settings_io.hpp"
 #include "util/ObjectsKeeper.hpp"
+#include "Time.hpp"
 
 #include <filesystem>
 #include <memory>
@@ -23,7 +24,6 @@
 class Screen;
 class EnginePaths;
 class ResPaths;
-class Batch2D;
 class EngineController;
 class SettingsHandler;
 struct EngineSettings;
@@ -70,17 +70,12 @@ class Engine : public util::ObjectsKeeper {
     std::unique_ptr<network::Network> network;
     std::vector<std::string> basePacks;
     std::unique_ptr<gui::GUI> gui;
-
-    uint64_t frame = 0;
-    double lastTime = 0.0;
-    double delta = 0.0;
+    Time time;
     
     void loadControls();
     void loadSettings();
     void saveSettings();
-    void updateTimers();
     void updateHotkeys();
-    void renderFrame(Batch2D& batch);
     void processPostRunnables();
     void loadAssets();
 public:
@@ -90,11 +85,11 @@ public:
     /// @brief Start the engine
     void run();
 
-    /// @brief Start main engine input/update/render loop. 
-    /// Automatically sets MenuScreen
-    void mainloop();
+    void postUpdate();
 
-    void runTest();
+    void updateFrontend();
+    void renderFrame();
+    void nextFrame();
 
     /// @brief Called after assets loading when all engine systems are initialized
     void onAssetsLoaded();
@@ -122,11 +117,6 @@ public:
     /// @brief Collect all available content-packs from res/content
     void loadAllPacks();
 
-    /// @brief Get current frame delta-time
-    double getDelta() const;
-
-    double getUptime() const;
-
     /// @brief Get active assets storage instance
     Assets* getAssets();
     
@@ -169,5 +159,9 @@ public:
 
     network::Network& getNetwork();
 
+    Time& getTime();
+
     const CoreParameters& getCoreParameters() const;
+
+    bool isHeadless() const;
 };
diff --git a/src/frontend/debug_panel.cpp b/src/frontend/debug_panel.cpp
index 9043f5b9..c9f08203 100644
--- a/src/frontend/debug_panel.cpp
+++ b/src/frontend/debug_panel.cpp
@@ -56,7 +56,7 @@ std::shared_ptr<UINode> create_debug_panel(
     static std::wstring fpsString = L"";
 
     panel->listenInterval(0.016f, [engine]() {
-        fps = 1.0f / engine->getDelta();
+        fps = 1.0f / engine->getTime().getDelta();
         fpsMin = std::min(fps, fpsMin);
         fpsMax = std::max(fps, fpsMax);
     });
diff --git a/src/graphics/core/DrawContext.cpp b/src/graphics/core/DrawContext.cpp
index 7062ad56..936de95b 100644
--- a/src/graphics/core/DrawContext.cpp
+++ b/src/graphics/core/DrawContext.cpp
@@ -92,6 +92,9 @@ DrawContext DrawContext::sub(Flushable* flushable) const {
     ctx.parent = this;
     ctx.flushable = flushable;
     ctx.scissorsCount = 0;
+    if (auto batch2D = dynamic_cast<Batch2D*>(flushable)) {
+        ctx.g2d = batch2D;
+    }
     return ctx;
 }
 
diff --git a/src/graphics/core/DrawContext.hpp b/src/graphics/core/DrawContext.hpp
index 736b053e..6c20f37f 100644
--- a/src/graphics/core/DrawContext.hpp
+++ b/src/graphics/core/DrawContext.hpp
@@ -10,7 +10,7 @@ class Framebuffer;
 class DrawContext {
     const DrawContext* parent;
     Viewport viewport;
-    Batch2D* const g2d;
+    Batch2D* g2d;
     Flushable* flushable = nullptr;
     Framebuffer* fbo = nullptr;
     bool depthMask = true;
diff --git a/src/graphics/ui/GUI.cpp b/src/graphics/ui/GUI.cpp
index 38bc2257..49a362e3 100644
--- a/src/graphics/ui/GUI.cpp
+++ b/src/graphics/ui/GUI.cpp
@@ -23,7 +23,7 @@
 
 using namespace gui;
 
-GUI::GUI() {
+GUI::GUI() : batch2D(std::make_unique<Batch2D>(1024)) {
     container = std::make_shared<Container>(glm::vec2(1000));
     uicamera = std::make_unique<Camera>(glm::vec3(), Window::height);
     uicamera->perspective = false;
@@ -198,7 +198,9 @@ void GUI::act(float delta, const Viewport& vp) {
 }
 
 void GUI::draw(const DrawContext& pctx, const Assets& assets) {
-    auto& viewport = pctx.getViewport();
+    auto ctx = pctx.sub(batch2D.get());
+
+    auto& viewport = ctx.getViewport();
     glm::vec2 wsize = viewport.size();
 
     menu->setPos((wsize - menu->getSize()) / 2.0f);
@@ -208,8 +210,8 @@ void GUI::draw(const DrawContext& pctx, const Assets& assets) {
     uishader->use();
     uishader->uniformMatrix("u_projview", uicamera->getProjView());
 
-    pctx.getBatch2D()->begin();
-    container->draw(pctx, assets);
+    batch2D->begin();
+    container->draw(ctx, assets);
 }
 
 std::shared_ptr<UINode> GUI::getFocused() const {
diff --git a/src/graphics/ui/GUI.hpp b/src/graphics/ui/GUI.hpp
index c0dec649..851a49f7 100644
--- a/src/graphics/ui/GUI.hpp
+++ b/src/graphics/ui/GUI.hpp
@@ -13,6 +13,7 @@ class Viewport;
 class DrawContext;
 class Assets;
 class Camera;
+class Batch2D;
 
 /*
  Some info about padding and margin.
@@ -52,6 +53,7 @@ namespace gui {
 
     /// @brief The main UI controller
     class GUI {
+        std::unique_ptr<Batch2D> batch2D;
         std::shared_ptr<Container> container;
         std::shared_ptr<UINode> hover;
         std::shared_ptr<UINode> pressed;
diff --git a/src/logic/EngineController.cpp b/src/logic/EngineController.cpp
index 4c38fc78..edd6efb7 100644
--- a/src/logic/EngineController.cpp
+++ b/src/logic/EngineController.cpp
@@ -132,13 +132,18 @@ static void show_content_missing(
     menus::show(engine, "reports/missing_content", {std::move(root)});
 }
 
-static bool loadWorldContent(Engine* engine, const fs::path& folder) {
-    return menus::call(engine, [engine, folder]() {
+static bool load_world_content(Engine* engine, const fs::path& folder) {
+    if (engine->isHeadless()) {
         engine->loadWorldContent(folder);
-    });
+        return true;
+    } else {
+        return menus::call(engine, [engine, folder]() {
+            engine->loadWorldContent(folder);
+        });
+    }
 }
 
-static void loadWorld(Engine* engine, const std::shared_ptr<WorldFiles>& worldFiles) {
+static void load_world(Engine* engine, const std::shared_ptr<WorldFiles>& worldFiles) {
     try {
         auto content = engine->getContent();
         auto& packs = engine->getContentPacks();
@@ -160,7 +165,12 @@ static void loadWorld(Engine* engine, const std::shared_ptr<WorldFiles>& worldFi
 void EngineController::openWorld(const std::string& name, bool confirmConvert) {
     auto paths = engine->getPaths();
     auto folder = paths->getWorldsFolder() / fs::u8path(name);
-    if (!loadWorldContent(engine, folder)) {
+    auto worldFile = folder / fs::u8path("world.json");
+    if (!fs::exists(worldFile)) {
+        throw std::runtime_error(worldFile.u8string() + " does not exists");
+    }
+
+    if (!load_world_content(engine, folder)) {
         return;
     }
 
@@ -192,7 +202,7 @@ void EngineController::openWorld(const std::string& name, bool confirmConvert) {
         }
         return;
     }
-    loadWorld(engine, std::move(worldFiles));
+    load_world(engine, std::move(worldFiles));
 }
 
 inline uint64_t str2seed(const std::string& seedstr) {
diff --git a/src/logic/scripting/lua/libs/libtime.cpp b/src/logic/scripting/lua/libs/libtime.cpp
index 45ed4288..daac093f 100644
--- a/src/logic/scripting/lua/libs/libtime.cpp
+++ b/src/logic/scripting/lua/libs/libtime.cpp
@@ -5,11 +5,11 @@
 using namespace scripting;
 
 static int l_uptime(lua::State* L) {
-    return lua::pushnumber(L, engine->getUptime());
+    return lua::pushnumber(L, engine->getTime().getTime());
 }
 
 static int l_delta(lua::State* L) {
-    return lua::pushnumber(L, engine->getDelta());
+    return lua::pushnumber(L, engine->getTime().getDelta());
 }
 
 const luaL_Reg timelib[] = {