diff --git a/doc/en/content-packs.md b/doc/en/content-packs.md
index a41f95f9..c193fb18 100644
--- a/doc/en/content-packs.md
+++ b/doc/en/content-packs.md
@@ -48,6 +48,79 @@ Example:
 
 Content pack picture should be added as *icon.png* file. Recommended size: 128x128
 
-See *res/content/base* as an example of content pack structure.
+# File System
 
+Every loaded pack is mounted to the internal file system as a new mount point, whose name matches the pack's id.
 
+This means that accessing pack files does not require the use of additional functions:
+
+```lua
+print(file.read("your_pack_id:package.json")) -- will output the contents of the pack's package.json
+```
+
+This is also one of the reasons why some ids are reserved and cannot be used.
+
+Mount points are mounted as read-only. To gain write access, use the `pack.request_writeable` function.
+
+Read more about the [file](scripting/builtins/libfile.md) library.
+
+# Content Pack Structure
+
+Don't be intimidated by the following text, as a minimal pack only requires `package.json`.
+
+- Content:
+    - `block_materials/` - Block material definitions
+    - `blocks/` - Block definitions
+    - `items/` - Item definitions
+    - `generators/` - World generators
+    - `entities/` - Entity definitions
+    - `skeletons/` - Entity skeleton definitions
+    - `presets/` - Presets (can also be used by packs for their own purposes)
+        - `text3d/` - 3D Text
+        - `weather/` - Weather
+- Code:
+    - `modules/` - Script modules
+    - `scripts/` - Content scripts, world scripts
+        - `components/` - Entity components
+- Assets (Client-side resources):
+    - `fonts/` - Fonts
+    - `models/` - 3D Models
+    - `textures/` - Textures
+    - `shaders/` - Shaders
+        - `effects/` - Post-processing effects
+    - `sounds/` - Sounds and Music
+    - `texts/` - Localization files
+- GUI:
+    - `layouts/` - UI Layouts
+        - `pages/` - Menu page layouts (for the pagebox element)
+- Configuration:
+    - `config/` - Configuration files
+        - `defaults.toml` - Overrides for standard content bindings, such as the player entity, default generator, etc.
+        - `bindings.toml` - Keyboard/Mouse bindings
+        - `user-props.toml` - User properties for content definitions
+    - `devtools/` - Auxiliary files for internal debugging tools
+    - `content.json` - Automatically generated content lists, used for validating world indices and for conversion when mismatched
+    - `icon.png` - Pack icon
+    - `package.json` - Pack definition file
+    - `preload.json` - Asset preload lists for assets that are not loaded automatically; avoid listing assets unnecessarily
+    - `resources.json` - Definition lists for [resources](resources.md) (not to be confused with assets)
+    - `resource-aliases.json` - Files declaring aliases for [resources](resources.md)
+
+> [!WARNING]
+> Manually editing `content.json` is strongly discouraged and will most likely lead to irreversible world corruption.
+
+# Content Sources
+
+Content packs are searched for within **content sources**, which are paths in the engine's file system.
+
+Source priority determines the scan order: if the same pack is found in multiple sources, the one belonging to the source with the highest priority will be selected.
+
+Content sources in descending order of priority:
+- `world:content` - Content in the world folder (`world/content/`)
+- `user:content` - Content in the user folder (`$HOME/.voxeng/content/`)
+- `project:content` - Content in the project folder (`project/content/`)
+- `res:content` - Built-in content shipped with the engine core (`res/content/`)
+
+I.e., if the same pack exists in both `world:content` and `user:content`, the version from `world:content` will be selected.
+
+The pack version, however, is currently not taken into account.
diff --git a/doc/en/scripting/builtins/libhud.md b/doc/en/scripting/builtins/libhud.md
index 58d78302..a7e3fa85 100644
--- a/doc/en/scripting/builtins/libhud.md
+++ b/doc/en/scripting/builtins/libhud.md
@@ -20,6 +20,12 @@ hud.open(
     [optional] invid: int
 ) -> int
 
+-- Returns true if specified layout is open.
+hud.is_open(
+    layoutid: str
+) -> bool
+
+
 -- Open block UI and inventory.
 -- Throws an exception if block has no UI layout.
 -- Returns block inventory ID (if *"inventory-size"=0* a virtual 
diff --git a/doc/ru/content-packs.md b/doc/ru/content-packs.md
index 4245555f..32f9be59 100644
--- a/doc/ru/content-packs.md
+++ b/doc/ru/content-packs.md
@@ -50,5 +50,80 @@
 
 Изображение контент-пака добавляется в виде файла *icon.png* в папку пака (не в textures). Рекомендованный размер изображения: 128x128
 
-Новые блоки добавляются в под-папку **blocks**, предметы в **items**, текстуры в **textures**
-С примером файловой структуры лучше ознакомиться через базовый пакет (*res/content/base*)
+# Файловая система
+
+Каждый загруженный пак монтируется к внутренней файловой системе как новая точка входа, имя которой совпадает с id пака.
+
+Это значит, что для доступа к файлам пака не требуется использование дополнительных функций:
+
+```lua
+print(file.read("пак:package.json")) -- выведет содержимое package.json пака
+```
+
+Также это является одной из причин того, что некоторые id зарезервированы от использования.
+
+Точки входа монтируются как read-only. Для получения доступа к записи существует функция pack.request_writeable.
+
+Подробнее про библиотеку [file](scripting/builtins/libfile.md).
+
+# Структура контент-пака
+
+Пусть вас не пугает следующий текст, ведь минимальный пак содержит только package.json.
+
+- Контент:
+    - `block_materials/` - определения материалов блоков
+    - `blocks/` - определения блоков
+    - `items/` - определения предметов
+    - `generators/` - генераторы мира
+    - `entities/` - определения сущностей
+    - `skeletons/` - определения скелетов сущностей
+    - `presets/` - пресеты (может использоваться и паками в своих целях)
+        - `text3d/` - 3D текст
+        - `weather/` - погода
+- Код:
+    - `modules/` - скриптовые модули
+    - `scripts/` - скрипты контента, мира
+        - `components/` - компоненты сущностей
+- Ассеты (ресурсы клиентской стороны):
+    - `fonts/` - шрифты
+    - `models/` - 3D модели
+    - `textures/` - текстуры
+    - `shaders/` - шейдеры
+        - `effects/` - эффекты пост-обработки
+    - `sounds/` - звуки и музыка
+    - `texts/` - файлы локализации
+- GUI:
+    - `layouts/` - макеты UI
+        - `pages/` - макеты страниц меню (элемент pagebox)
+- Конфигурация:
+    - `config/` - файлы конфигурации
+        - `defaults.toml` - переопределения стандартных привязок к контенту, такие как сущность игрока, генератор по-умолчанию и т.д.
+        - `bindings.toml` - привязки к клавишам / мыши
+        - `user-props.toml` - пользовательские свойства определений контента
+    - `devtools/` - вспомогательные файлы внутренних инструментов отладки
+    - `content.json` - генерируемые автоматически списки контента, используемое для проверки корректности индексов в мире и конвертации при несовпадении
+    - `icon.png` - иконка пака
+    - `package.json` - файл опеределения пака
+    - `preload.json` - списки предзагрузки ассетов, которые не загружаются автоматически, не следует указывать ассеты без надобности
+    - `resources.json` - списки определений [ресурсов](resources.md) (не путать с ассетами)
+    - `resource-aliases.json` - файлы объявления псевдонимов для [ресурсов](resources.md)
+
+> [!WARNING]
+> Ручное редактирование `content.json` противопоказано и скорее всего приведёт к необратимой поломке миров.
+
+# Источники контента
+
+Поиск контент-паков производится среди **источников контента**, являющихся путями в файловой системе движка.
+
+Приоритет источника определяет порядок сканирования: если один и тот же пак найден в нескольких источниках, 
+будет выбран тот, что принадлежит источнику с наивысшим приоритетом.
+
+Источники контента в порядке убывания приоритета:
+- `world:content` - контент папке с миром (`мир/content/`)
+- `user:content` - контент в папке пользователя (`$HOME/.voxeng/content/`)
+- `project:content` - контент в папке с проектом (`проект/content/`)
+- `res:content` - встроенный контент, поставляемый вместе с ядром движка (`res/content/`)
+
+Т.е. если в `world:content` и в `user:content` есть один и тот же пак, будет выбрана версия из `world:content`.
+
+Версия пака, при этом, на данный момент, не учитывается.
diff --git a/doc/ru/scripting/builtins/libhud.md b/doc/ru/scripting/builtins/libhud.md
index 5f0856b3..6ed81e05 100644
--- a/doc/ru/scripting/builtins/libhud.md
+++ b/doc/ru/scripting/builtins/libhud.md
@@ -20,6 +20,10 @@ hud.open(
     [опционально] invid: int
 ) -> int
 
+-- Возвращает true если указаный макет UI открыт.
+hud.is_open(
+    layoutid: str
+) -> bool
 
 -- Открывает инвентарь и UI блока.
 -- Если блок не имеет макета UI - бросается исключение.
diff --git a/res/modules/internal/events.lua b/res/modules/internal/events.lua
index 7635af25..a0cd8276 100644
--- a/res/modules/internal/events.lua
+++ b/res/modules/internal/events.lua
@@ -2,7 +2,14 @@ local events = {
     handlers = {}
 }
 
+local __parse_path = parse_path
+local __pack_is_installed = pack.is_installed
+
 function events.on(event, func)
+    local prefix = __parse_path(event)
+    if prefix ~= "core" and not __pack_is_installed(prefix) then
+        error("pack prefix required")
+    end
     if events.handlers[event] == nil then
         events.handlers[event] = {}
     end
diff --git a/res/scripts/stdlib.lua b/res/scripts/stdlib.lua
index a81c1232..a9199132 100644
--- a/res/scripts/stdlib.lua
+++ b/res/scripts/stdlib.lua
@@ -114,7 +114,6 @@ events = require "core:internal/events"
 
 function pack.unload(prefix)
     events.remove_by_prefix(prefix)
-    __vc__pack_envs[prefix] = nil
 end
 
 function __vc_start_app_script(path)
diff --git a/res/scripts/stdmin.lua b/res/scripts/stdmin.lua
index 63409c36..4af92e1c 100644
--- a/res/scripts/stdmin.lua
+++ b/res/scripts/stdmin.lua
@@ -230,15 +230,37 @@ function require(path)
     return __load_script(prefix .. ":modules/" .. file .. ".lua", nil, env)
 end
 
-function __scripts_cleanup()
+-- TODO: move to string
+local function join(t, sep)
+    local s = ""
+    for i, v in ipairs(t) do
+        s = s..tostring(v)
+        if i < #t then
+            s = s..sep
+        end
+    end
+    return s
+end
+
+function __scripts_cleanup(non_reset_packs)
     debug.log("cleaning scripts cache")
+    if #non_reset_packs == 0 then
+        debug.log("no non-reset packs")
+    else
+        debug.log("non-reset packs: "..join(non_reset_packs, ", "))
+    end
     for k, v in pairs(__cached_scripts) do
         local packname, _ = parse_path(k)
+        if table.has(non_reset_packs, packname) then
+            goto continue
+        end
         if packname ~= "core" then
             debug.log("unloaded "..k)
             __cached_scripts[k] = nil
             package.loaded[k] = nil
         end
+        __vc__pack_envs[packname] = nil
+        ::continue::
     end
 end
 
diff --git a/src/assets/AssetsLoader.cpp b/src/assets/AssetsLoader.cpp
index 8dc7c31c..0fde22fc 100644
--- a/src/assets/AssetsLoader.cpp
+++ b/src/assets/AssetsLoader.cpp
@@ -9,7 +9,7 @@
 #include "content/Content.hpp"
 #include "content/ContentPack.hpp"
 #include "debug/Logger.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "graphics/core/Texture.hpp"
 #include "logic/scripting/scripting.hpp"
diff --git a/src/assets/assetload_funcs.cpp b/src/assets/assetload_funcs.cpp
index 4fda3b0d..a1c04dfc 100644
--- a/src/assets/assetload_funcs.cpp
+++ b/src/assets/assetload_funcs.cpp
@@ -15,7 +15,7 @@
 #include "coders/vec3.hpp"
 #include "constants.hpp"
 #include "debug/Logger.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "frontend/UiDocument.hpp"
 #include "graphics/core/Atlas.hpp"
diff --git a/src/coders/GLSLExtension.cpp b/src/coders/GLSLExtension.cpp
index 5d53cb35..fa1335f3 100644
--- a/src/coders/GLSLExtension.cpp
+++ b/src/coders/GLSLExtension.cpp
@@ -6,7 +6,7 @@
 #include <utility>
 
 #include "debug/Logger.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "typedefs.hpp"
 #include "util/stringutil.hpp"
 #include "coders/json.hpp"
diff --git a/src/content/ContentControl.cpp b/src/content/ContentControl.cpp
index 9c99135b..c887baa6 100644
--- a/src/content/ContentControl.cpp
+++ b/src/content/ContentControl.cpp
@@ -1,7 +1,7 @@
 #include "ContentControl.hpp"
 
 #include "io/io.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "Content.hpp"
 #include "ContentPack.hpp"
 #include "ContentBuilder.hpp"
@@ -30,6 +30,7 @@ ContentControl::ContentControl(
     manager->setSources({
         "world:content",
         "user:content",
+        "project:content",
         "res:content",
     });
 }
@@ -48,10 +49,10 @@ std::vector<std::string>& ContentControl::getBasePacks() {
     return basePacks;
 }
 
-void ContentControl::resetContent() {
+void ContentControl::resetContent(const std::vector<std::string>& nonReset) {
     paths.setCurrentWorldFolder("");
 
-    scripting::cleanup();
+    scripting::cleanup(nonReset);
     std::vector<PathsRoot> resRoots;
     {
         auto pack = ContentPack::createCore();
@@ -78,8 +79,6 @@ void ContentControl::loadContent(const std::vector<std::string>& names) {
 }
 
 void ContentControl::loadContent() {
-    scripting::cleanup();
-
     std::vector<std::string> names;
     for (auto& pack : contentPacks) {
         names.push_back(pack.id);
diff --git a/src/content/ContentControl.hpp b/src/content/ContentControl.hpp
index ef45a04a..f066601e 100644
--- a/src/content/ContentControl.hpp
+++ b/src/content/ContentControl.hpp
@@ -34,7 +34,7 @@ public:
     std::vector<std::string>& getBasePacks();
 
     /// @brief Reset content to base packs list
-    void resetContent();
+    void resetContent(const std::vector<std::string>& nonReset);
 
     void loadContent(const std::vector<std::string>& names);
 
diff --git a/src/content/ContentLoader.cpp b/src/content/ContentLoader.cpp
index ea29e27c..a88146be 100644
--- a/src/content/ContentLoader.cpp
+++ b/src/content/ContentLoader.cpp
@@ -13,7 +13,7 @@
 #include "objects/rigging.hpp"
 #include "util/listutil.hpp"
 #include "util/stringutil.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 
 static debug::Logger logger("content-loader");
 
diff --git a/src/content/ContentPack.cpp b/src/content/ContentPack.cpp
index 021f083e..d2ffdc9e 100644
--- a/src/content/ContentPack.cpp
+++ b/src/content/ContentPack.cpp
@@ -8,7 +8,7 @@
 #include "coders/json.hpp"
 #include "constants.hpp"
 #include "data/dv.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "coders/commons.hpp"
 #include "debug/Logger.hpp"
diff --git a/src/content/loading/GeneratorLoader.cpp b/src/content/loading/GeneratorLoader.cpp
index 2f8f40d5..668425e0 100644
--- a/src/content/loading/GeneratorLoader.cpp
+++ b/src/content/loading/GeneratorLoader.cpp
@@ -6,7 +6,7 @@
 #include "../ContentPack.hpp"
 
 #include "io/io.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "logic/scripting/scripting.hpp"
 #include "util/stringutil.hpp"
 #include "world/generator/GeneratorDef.hpp"
diff --git a/src/core_defs.cpp b/src/core_defs.cpp
index 79551cd4..a72d6eef 100644
--- a/src/core_defs.cpp
+++ b/src/core_defs.cpp
@@ -4,7 +4,7 @@
 #include "content/Content.hpp"
 #include "content/ContentBuilder.hpp"
 #include "io/io.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "window/input.hpp"
 #include "voxels/Block.hpp"
 #include "coders/toml.hpp"
diff --git a/src/devtools/Editor.cpp b/src/devtools/Editor.cpp
index 82475ee4..0bd0af7d 100644
--- a/src/devtools/Editor.cpp
+++ b/src/devtools/Editor.cpp
@@ -1,7 +1,7 @@
 #include "Editor.hpp"
 
 #include "engine/Engine.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "coders/syntax_parser.hpp"
 #include "SyntaxProcessor.hpp"
 
diff --git a/src/devtools/Project.cpp b/src/devtools/Project.cpp
index 881f6cc7..61e99c6a 100644
--- a/src/devtools/Project.cpp
+++ b/src/devtools/Project.cpp
@@ -1,8 +1,13 @@
 #include "Project.hpp"
 
 #include "data/dv_util.hpp"
+#include "debug/Logger.hpp"
+#include "io/io.hpp"
+#include "io/path.hpp"
 #include "logic/scripting/scripting.hpp"
 
+static debug::Logger logger("project");
+
 Project::~Project() = default;
 
 dv::value Project::serialize() const {
@@ -18,3 +23,23 @@ void Project::deserialize(const dv::value& src) {
     src.at("title").get(title);
     dv::get(src, "base_packs", basePacks);
 }
+
+void Project::loadProjectClientScript() {
+    io::path scriptFile = "project:project_client.lua";
+    if (io::exists(scriptFile)) {
+        logger.info() << "starting project client script";
+        clientScript = scripting::load_client_project_script(scriptFile);
+    } else {
+        logger.warning() << "project client script does not exists";
+    }
+}
+
+void Project::loadProjectStartScript() {
+    io::path scriptFile = "project:start.lua";
+    if (io::exists(scriptFile)) {
+        logger.info() << "starting project start script";
+        setupCoroutine = scripting::start_app_script(scriptFile);
+    } else {
+        logger.warning() << "project start script does not exists";
+    }
+}
diff --git a/src/devtools/Project.hpp b/src/devtools/Project.hpp
index be9d88a3..f0851b30 100644
--- a/src/devtools/Project.hpp
+++ b/src/devtools/Project.hpp
@@ -4,6 +4,7 @@
 #include <vector>
 #include <memory>
 
+#include "interfaces/Process.hpp"
 #include "interfaces/Serializable.hpp"
 
 namespace scripting {
@@ -15,9 +16,13 @@ struct Project : Serializable {
     std::string title;
     std::vector<std::string> basePacks;
     std::unique_ptr<scripting::IClientProjectScript> clientScript;
+    std::unique_ptr<Process> setupCoroutine;
 
     ~Project();
 
     dv::value serialize() const override;
     void deserialize(const dv::value& src) override;
+
+    void loadProjectClientScript();
+    void loadProjectStartScript();
 };
diff --git a/src/engine/CoreParameters.hpp b/src/engine/CoreParameters.hpp
new file mode 100644
index 00000000..c937bf3a
--- /dev/null
+++ b/src/engine/CoreParameters.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <string>
+#include <filesystem>
+
+struct CoreParameters {
+    bool headless = false;
+    bool testMode = false;
+    std::filesystem::path resFolder = "res";
+    std::filesystem::path userFolder = ".";
+    std::filesystem::path scriptFile;
+    std::filesystem::path projectFolder;
+    std::string debugServerString;
+    int tps = 20;
+};
diff --git a/src/engine/Engine.cpp b/src/engine/Engine.cpp
index 3053b613..6598562f 100644
--- a/src/engine/Engine.cpp
+++ b/src/engine/Engine.cpp
@@ -8,8 +8,6 @@
 #include "assets/AssetsLoader.hpp"
 #include "audio/audio.hpp"
 #include "coders/GLSLExtension.hpp"
-#include "coders/imageio.hpp"
-#include "coders/json.hpp"
 #include "coders/toml.hpp"
 #include "coders/commons.hpp"
 #include "devtools/Editor.hpp"
@@ -18,28 +16,28 @@
 #include "content/ContentControl.hpp"
 #include "core_defs.hpp"
 #include "io/io.hpp"
+#include "io/settings_io.hpp"
 #include "frontend/locale.hpp"
 #include "frontend/menu.hpp"
 #include "frontend/screens/Screen.hpp"
 #include "graphics/render/ModelsGenerator.hpp"
 #include "graphics/core/DrawContext.hpp"
-#include "graphics/core/ImageData.hpp"
 #include "graphics/core/Shader.hpp"
 #include "graphics/ui/GUI.hpp"
 #include "graphics/ui/elements/Menu.hpp"
-#include "objects/rigging.hpp"
 #include "logic/EngineController.hpp"
 #include "logic/CommandsInterpreter.hpp"
 #include "logic/scripting/scripting.hpp"
 #include "logic/scripting/scripting_hud.hpp"
 #include "network/Network.hpp"
 #include "util/platform.hpp"
-#include "window/Camera.hpp"
 #include "window/input.hpp"
 #include "window/Window.hpp"
 #include "world/Level.hpp"
 #include "Mainloop.hpp"
 #include "ServerMainloop.hpp"
+#include "WindowControl.hpp"
+#include "EnginePaths.hpp"
 
 #include <iostream>
 #include <assert.h>
@@ -50,29 +48,6 @@
 
 static debug::Logger logger("engine");
 
-static std::unique_ptr<ImageData> load_icon() {
-    try {
-        auto file = "res:textures/misc/icon.png";
-        if (io::exists(file)) {
-            return imageio::read(file);
-        }
-    } catch (const std::exception& err) {
-        logger.error() << "could not load window icon: " << err.what();
-    }
-    return nullptr;
-}
-
-static std::unique_ptr<scripting::IClientProjectScript> load_client_project_script() {
-    io::path scriptFile = "project:project_client.lua";
-    if (io::exists(scriptFile)) {
-        logger.info() << "starting project script";
-        return scripting::load_client_project_script(scriptFile);
-    } else {
-        logger.warning() << "project script does not exists";
-    }
-    return nullptr;
-}
-
 Engine::Engine() = default;
 Engine::~Engine() = default;
 
@@ -87,7 +62,7 @@ Engine& Engine::getInstance() {
 
 void Engine::onContentLoad() {
     editor->loadTools();
-    langs::setup(langs::get_current(), paths.resPaths.collectRoots());
+    langs::setup(langs::get_current(), paths->resPaths.collectRoots());
     
     if (isHeadless()) {
         return;
@@ -108,29 +83,9 @@ void Engine::onContentLoad() {
 }
 
 void Engine::initializeClient() {
-    std::string title = project->title;
-    if (title.empty()) {
-        title = "VoxelCore v" +
-                        std::to_string(ENGINE_VERSION_MAJOR) + "." +
-                        std::to_string(ENGINE_VERSION_MINOR);
-    }
-    if (ENGINE_DEBUG_BUILD) {
-        title += " [debug]";
-    }
-    if (debuggingServer) {
-        title = "[debugging] " + title;
-    }
-    auto [window, input] = Window::initialize(&settings.display, title);
-    if (!window || !input){
-        throw initialize_error("could not initialize window");
-    }
-    window->setFramerate(settings.display.framerate.get());
+    windowControl = std::make_unique<WindowControl>(*this);
+    auto [window, input] = windowControl->initialize();
 
-    time.set(window->time());
-    if (auto icon = load_icon()) {
-        icon->flipY();
-        window->setIcon(icon.get());
-    }
     this->window = std::move(window);
     this->input = std::move(input);
 
@@ -171,15 +126,12 @@ void Engine::initialize(CoreParameters coreParameters) {
 
     logger.info() << "engine version: " << ENGINE_VERSION_STRING;
     if (params.headless) {
-        logger.info() << "headless mode is enabled";
+        logger.info() << "engine runs in headless mode";
     }
     if (params.projectFolder.empty()) {
         params.projectFolder = params.resFolder;
     }
-    paths.setResourcesFolder(params.resFolder);
-    paths.setUserFilesFolder(params.userFolder);
-    paths.setProjectFolder(params.projectFolder);
-    paths.prepare();
+    paths = std::make_unique<EnginePaths>(params);
     loadProject();
 
     editor = std::make_unique<devtools::Editor>(*this);
@@ -197,10 +149,6 @@ void Engine::initialize(CoreParameters coreParameters) {
             );
         }
     }
-
-    if (!params.scriptFile.empty()) {
-        paths.setScriptFolder(params.scriptFile.parent_path());
-    }
     loadSettings();
 
     controller = std::make_unique<EngineController>(*this);
@@ -214,7 +162,7 @@ void Engine::initialize(CoreParameters coreParameters) {
             langs::locale_by_envlocale(platform::detect_locale())
         );
     }
-    content = std::make_unique<ContentControl>(*project, paths, *input, [this]() {
+    content = std::make_unique<ContentControl>(*project, *paths, *input, [this]() {
         onContentLoad();
     });
     scripting::initialize(this);
@@ -223,10 +171,13 @@ void Engine::initialize(CoreParameters coreParameters) {
         gui->setPageLoader(scripting::create_page_loader());
     }
     keepAlive(settings.ui.language.observe([this](auto lang) {
-        langs::setup(lang, paths.resPaths.collectRoots());
+        langs::setup(lang, paths->resPaths.collectRoots());
     }, true));
 
-    project->clientScript = load_client_project_script();
+    project->loadProjectStartScript();
+    if (!params.headless) {
+        project->loadProjectClientScript();
+    }
 }
 
 void Engine::loadSettings() {
@@ -256,29 +207,17 @@ void Engine::loadControls() {
 
 void Engine::updateHotkeys() {
     if (input->jpressed(Keycode::F2)) {
-        saveScreenshot();
+        windowControl->saveScreenshot();
     }
     if (input->pressed(Keycode::LEFT_CONTROL) && input->pressed(Keycode::F3) &&
         input->jpressed(Keycode::U)) {
         gui->toggleDebug();
     }
     if (input->jpressed(Keycode::F11)) {
-        if (settings.display.windowMode.get() != static_cast<int>(WindowMode::FULLSCREEN)) {
-            settings.display.windowMode.set(static_cast<int>(WindowMode::FULLSCREEN));
-        } else {
-            settings.display.windowMode.set(static_cast<int>(WindowMode::WINDOWED));
-        }
+        windowControl->toggleFullscreen();
     }
 }
 
-void Engine::saveScreenshot() {
-    auto image = window->takeScreenshot();
-    image->flipY();
-    io::path filename = paths.getNewScreenshotFile("png");
-    imageio::write(filename.string(), image.get());
-    logger.info() << "saved screenshot as " << filename.string();
-}
-
 void Engine::run() {
     if (params.headless) {
         ServerMainloop(*this).run();
@@ -301,6 +240,12 @@ void Engine::detachDebugger() {
     debuggingServer.reset();
 }
 
+void Engine::applicationTick() {
+    if (project->setupCoroutine && project->setupCoroutine->isActive()) {
+        project->setupCoroutine->update();
+    }
+}
+
 void Engine::updateFrontend() {
     double delta = time.getDelta();
     updateHotkeys();
@@ -310,14 +255,8 @@ void Engine::updateFrontend() {
     gui->postAct();
 }
 
-void Engine::nextFrame() {
-    window->setFramerate(
-        window->isIconified() && settings.display.limitFpsIconified.get()
-            ? 20
-            : settings.display.framerate.get()
-    );
-    window->swapBuffers();
-    input->pollEvents();
+void Engine::nextFrame(bool waitForRefresh) {
+    windowControl->nextFrame(waitForRefresh);
 }
 
 void Engine::startPauseLoop() {
@@ -336,7 +275,7 @@ void Engine::startPauseLoop() {
         if (isHeadless()) {
             platform::sleep(1.0 / params.tps * 1000);
         } else {
-            nextFrame();
+            nextFrame(false);
         }
     }
     if (initialCursorLocked) {
@@ -407,17 +346,18 @@ void Engine::setLevelConsumer(OnWorldOpen levelConsumer) {
 
 void Engine::loadAssets() {
     logger.info() << "loading assets";
-    Shader::preprocessor->setPaths(&paths.resPaths);
+    Shader::preprocessor->setPaths(&paths->resPaths);
 
     auto content = this->content->get();
 
     auto new_assets = std::make_unique<Assets>();
-    AssetsLoader loader(*this, *new_assets, paths.resPaths);
+    AssetsLoader loader(*this, *new_assets, paths->resPaths);
     AssetsLoader::addDefaults(loader, content);
 
     // no need
     // correct log messages order is more useful
-    bool threading = false; // look at two upper lines
+    // todo: before setting to true, check if GLSLExtension thread safe
+    bool threading = false; // look at three upper lines
     if (threading) {
         auto task = loader.startTask([=](){});
         task->waitForEnd();
@@ -454,6 +394,7 @@ void Engine::setScreen(std::shared_ptr<Screen> screen) {
     }
     if (project->clientScript && this->screen) {
         project->clientScript->onScreenChange(this->screen->getName(), true);
+        window->setShouldRefresh();
     }
 }
 
@@ -487,11 +428,11 @@ Assets* Engine::getAssets() {
 }
 
 EnginePaths& Engine::getPaths() {
-    return paths;
+    return *paths;
 }
 
 ResPaths& Engine::getResPaths() {
-    return paths.resPaths;
+    return paths->resPaths;
 }
 
 std::shared_ptr<Screen> Engine::getScreen() {
diff --git a/src/engine/Engine.hpp b/src/engine/Engine.hpp
index 98a2c3ef..6b09b2ca 100644
--- a/src/engine/Engine.hpp
+++ b/src/engine/Engine.hpp
@@ -1,25 +1,27 @@
 #pragma once
 
-#include "delegates.hpp"
-#include "typedefs.hpp"
-#include "settings.hpp"
-
-#include "io/engine_paths.hpp"
-#include "io/settings_io.hpp"
-#include "util/ObjectsKeeper.hpp"
+#include "CoreParameters.hpp"
 #include "PostRunnables.hpp"
 #include "Time.hpp"
+#include "delegates.hpp"
+#include "settings.hpp"
+#include "typedefs.hpp"
+#include "util/ObjectsKeeper.hpp"
 
 #include <memory>
 #include <string>
 
-class Window;
 class Assets;
-class Level;
-class Screen;
 class ContentControl;
 class EngineController;
+class EnginePaths;
 class Input;
+class Level;
+class ResPaths;
+class Screen;
+class SettingsHandler;
+class Window;
+class WindowControl;
 struct Project;
 
 namespace gui {
@@ -44,24 +46,12 @@ public:
     initialize_error(const std::string& message) : std::runtime_error(message) {}
 };
 
-struct CoreParameters {
-    bool headless = false;
-    bool testMode = false;
-    std::filesystem::path resFolder = "res";
-    std::filesystem::path userFolder = ".";
-    std::filesystem::path scriptFile;
-    std::filesystem::path projectFolder;
-    std::string debugServerString;
-    int tps = 20;
-};
-
 using OnWorldOpen = std::function<void(std::unique_ptr<Level>, int64_t)>;
 
 class Engine : public util::ObjectsKeeper {
     CoreParameters params;
     EngineSettings settings;
-    EnginePaths paths;
-
+    std::unique_ptr<EnginePaths> paths;
     std::unique_ptr<Project> project;
     std::unique_ptr<SettingsHandler> settingsHandler;
     std::unique_ptr<Assets> assets;
@@ -75,6 +65,7 @@ class Engine : public util::ObjectsKeeper {
     std::unique_ptr<gui::GUI> gui;
     std::unique_ptr<devtools::Editor> editor;
     std::unique_ptr<devtools::DebuggingServer> debuggingServer;
+    std::unique_ptr<WindowControl> windowControl;
     PostRunnables postRunnables;
     Time time;
     OnWorldOpen levelConsumer;
@@ -105,9 +96,10 @@ public:
 
     void postUpdate();
 
+    void applicationTick();
     void updateFrontend();
     void renderFrame();
-    void nextFrame();
+    void nextFrame(bool waitForRefresh);
     void startPauseLoop();
     
     /// @brief Set screen (scene).
@@ -143,8 +135,6 @@ public:
         postRunnables.postRunnable(callback);
     }
 
-    void saveScreenshot();
-
     EngineController* getController();
 
     void setLevelConsumer(OnWorldOpen levelConsumer);
diff --git a/src/io/engine_paths.cpp b/src/engine/EnginePaths.cpp
similarity index 87%
rename from src/io/engine_paths.cpp
rename to src/engine/EnginePaths.cpp
index 98363d9b..8a786140 100644
--- a/src/io/engine_paths.cpp
+++ b/src/engine/EnginePaths.cpp
@@ -1,44 +1,56 @@
-#include "engine_paths.hpp"
+#include "EnginePaths.hpp"
+
+#include "debug/Logger.hpp"
+#include "io/devices/StdfsDevice.hpp"
+#include "io/devices/ZipFileDevice.hpp"
+#include "maths/util.hpp"
+#include "typedefs.hpp"
+#include "util/platform.hpp"
+#include "util/random.hpp"
+#include "util/stringutil.hpp"
+#include "world/files/WorldFiles.hpp"
 
 #include <algorithm>
 #include <array>
+#include <chrono>
 #include <sstream>
 #include <stack>
-#include "typedefs.hpp"
-#include "util/stringutil.hpp"
-#include "util/platform.hpp"
+#include <stdexcept>
 #include <utility>
 
-#include "io/devices/StdfsDevice.hpp"
-#include "io/devices/ZipFileDevice.hpp"
-#include "world/files/WorldFiles.hpp"
-#include "debug/Logger.hpp"
-
-#include <chrono>
-#include "maths/util.hpp"
-
-template<int n>
-static std::string generate_random_base64() {
-    auto now = std::chrono::high_resolution_clock::now();
-    auto seed = now.time_since_epoch().count();
-
-    util::PseudoRandom random(seed); // fixme: replace with safe random
-    ubyte bytes[n];
-    random.rand(bytes, n);
-    return util::base64_urlsafe_encode(bytes, n);
-}
-
 namespace fs = std::filesystem;
 
-static debug::Logger logger("engine-paths");
+static std::random_device random_device;
 
 static inline io::path SCREENSHOTS_FOLDER = "user:screenshots";
 static inline io::path CONTENT_FOLDER = "user:content";
 static inline io::path WORLDS_FOLDER = "user:worlds";
 
-void EnginePaths::prepare() {
+static debug::Logger logger("engine-paths");
+
+template<int n>
+static std::string generate_random_base64() {
+    auto randomEngine = util::seeded_random_engine(random_device);
+    static std::uniform_int_distribution<integer_t> dist(0, 0xFF);
+    ubyte bytes[n];
+    for (size_t i = 0; i < n; i++) {
+        bytes[i] = dist(randomEngine);
+    }
+    return util::base64_urlsafe_encode(bytes, n);
+}
+
+EnginePaths::EnginePaths(CoreParameters& params)
+    : resourcesFolder(params.resFolder),
+      userFilesFolder(params.userFolder),
+      projectFolder(params.projectFolder) {
+    if (!params.scriptFile.empty()) {
+        scriptFolder = params.scriptFile.parent_path();
+        io::set_device("script", std::make_shared<io::StdfsDevice>(*scriptFolder));
+    }
+
     io::set_device("res", std::make_shared<io::StdfsDevice>(resourcesFolder, false));
     io::set_device("user", std::make_shared<io::StdfsDevice>(userFilesFolder));
+    io::set_device("project", std::make_shared<io::StdfsDevice>(projectFolder));
 
     if (!io::is_directory("res:")) {
         throw std::runtime_error(
@@ -59,15 +71,7 @@ void EnginePaths::prepare() {
     io::create_subdevice("config", "user", "config");
 }
 
-const std::filesystem::path& EnginePaths::getUserFilesFolder() const {
-    return userFilesFolder;
-}
-
-const std::filesystem::path& EnginePaths::getResourcesFolder() const {
-    return resourcesFolder;
-}
-
-io::path EnginePaths::getNewScreenshotFile(const std::string& ext) {
+io::path EnginePaths::getNewScreenshotFile(const std::string& ext) const {
     auto folder = SCREENSHOTS_FOLDER;
     if (!io::is_directory(folder)) {
         io::create_directories(folder);
@@ -95,10 +99,6 @@ io::path EnginePaths::getWorldsFolder() const {
     return WORLDS_FOLDER;
 }
 
-io::path EnginePaths::getCurrentWorldFolder() {
-    return currentWorldFolder;
-}
-
 io::path EnginePaths::getWorldFolderByName(const std::string& name) {
     return getWorldsFolder() / name;
 }
@@ -132,24 +132,6 @@ std::vector<io::path> EnginePaths::scanForWorlds() const {
     return folders;
 }
 
-void EnginePaths::setUserFilesFolder(std::filesystem::path folder) {
-    this->userFilesFolder = std::move(folder);
-}
-
-void EnginePaths::setResourcesFolder(std::filesystem::path folder) {
-    this->resourcesFolder = std::move(folder);
-}
-
-void EnginePaths::setScriptFolder(std::filesystem::path folder) {
-    io::set_device("script", std::make_shared<io::StdfsDevice>(folder));
-    this->scriptFolder = std::move(folder);
-}
-
-void EnginePaths::setProjectFolder(std::filesystem::path folder) {
-    io::set_device("project", std::make_shared<io::StdfsDevice>(folder));
-    this->projectFolder = std::move(folder);
-}
-
 void EnginePaths::setCurrentWorldFolder(io::path folder) {
     if (folder.empty()) {
         io::remove_device("world");
diff --git a/src/io/engine_paths.hpp b/src/engine/EnginePaths.hpp
similarity index 73%
rename from src/io/engine_paths.hpp
rename to src/engine/EnginePaths.hpp
index 8b9b7f8e..41d02236 100644
--- a/src/io/engine_paths.hpp
+++ b/src/engine/EnginePaths.hpp
@@ -1,15 +1,15 @@
 #pragma once
 
+#include "io/io.hpp"
+#include "data/dv.hpp"
+#include "CoreParameters.hpp"
+
 #include <unordered_map>
-#include <stdexcept>
 #include <optional>
 #include <string>
 #include <vector>
 #include <tuple>
 
-#include "io.hpp"
-#include "data/dv.hpp"
-
 struct PathsRoot {
     std::string name;
     io::path path;
@@ -46,24 +46,13 @@ class EnginePaths {
 public:
     ResPaths resPaths;
 
-    void prepare();
-
-    void setUserFilesFolder(std::filesystem::path folder);
-    const std::filesystem::path& getUserFilesFolder() const;
-
-    void setResourcesFolder(std::filesystem::path folder);
-    const std::filesystem::path& getResourcesFolder() const;
-
-    void setScriptFolder(std::filesystem::path folder);
-
-    void setProjectFolder(std::filesystem::path folder);
+    EnginePaths(CoreParameters& params);
 
     io::path getWorldFolderByName(const std::string& name);
     io::path getWorldsFolder() const;
 
     void setCurrentWorldFolder(io::path folder);
-    io::path getCurrentWorldFolder();
-    io::path getNewScreenshotFile(const std::string& ext);
+    io::path getNewScreenshotFile(const std::string& ext) const;
 
     std::string mount(const io::path& file);
     void unmount(const std::string& name);
@@ -80,9 +69,9 @@ public:
     static inline io::path CONTROLS_FILE = "user:controls.toml";
     static inline io::path SETTINGS_FILE = "user:settings.toml";
 private:
-    std::filesystem::path userFilesFolder {"."};
-    std::filesystem::path resourcesFolder {"res"};
-    std::filesystem::path projectFolder = resourcesFolder;
+    std::filesystem::path resourcesFolder;
+    std::filesystem::path userFilesFolder;
+    std::filesystem::path projectFolder;
     io::path currentWorldFolder;
     std::optional<std::filesystem::path> scriptFolder;
     std::vector<PathsRoot> entryPoints;
diff --git a/src/engine/Mainloop.cpp b/src/engine/Mainloop.cpp
index a14c5464..d6ca17cb 100644
--- a/src/engine/Mainloop.cpp
+++ b/src/engine/Mainloop.cpp
@@ -18,6 +18,7 @@ Mainloop::Mainloop(Engine& engine) : engine(engine) {
 void Mainloop::run() {
     auto& time = engine.getTime();
     auto& window = engine.getWindow();
+    auto& settings = engine.getSettings();
 
     engine.setLevelConsumer([this](auto level, int64_t localPlayer) {
         if (level == nullptr) {
@@ -38,13 +39,17 @@ void Mainloop::run() {
     logger.info() << "main loop started";
     while (!window.isShouldClose()){
         time.update(window.time());
+        engine.applicationTick();
         engine.updateFrontend();
 
         if (!window.isIconified()) {
             engine.renderFrame();
         }
         engine.postUpdate();
-        engine.nextFrame();
+        engine.nextFrame(
+            settings.display.adaptiveFpsInMenu.get() &&
+            dynamic_cast<const MenuScreen*>(engine.getScreen().get()) != nullptr
+        );
     }
     logger.info() << "main loop stopped";
 }
diff --git a/src/engine/ServerMainloop.cpp b/src/engine/ServerMainloop.cpp
index ab35ffbd..41887aee 100644
--- a/src/engine/ServerMainloop.cpp
+++ b/src/engine/ServerMainloop.cpp
@@ -1,6 +1,7 @@
 #include "ServerMainloop.hpp"
 
 #include "Engine.hpp"
+#include "EnginePaths.hpp"
 #include "logic/scripting/scripting.hpp"
 #include "logic/LevelController.hpp"
 #include "interfaces/Process.hpp"
@@ -60,6 +61,7 @@ void ServerMainloop::run() {
             controller->getLevel()->getWorld()->updateTimers(delta);
             controller->update(glm::min(delta, 0.2), false);
         }
+        engine.applicationTick();
         engine.postUpdate();
 
         if (!coreParams.testMode) {
diff --git a/src/engine/WindowControl.cpp b/src/engine/WindowControl.cpp
new file mode 100644
index 00000000..5ae96965
--- /dev/null
+++ b/src/engine/WindowControl.cpp
@@ -0,0 +1,93 @@
+#include "WindowControl.hpp"
+
+#include "Engine.hpp"
+#include "engine/EnginePaths.hpp"
+#include "devtools/Project.hpp"
+#include "coders/imageio.hpp"
+#include "window/Window.hpp"
+#include "window/input.hpp"
+#include "debug/Logger.hpp"
+#include "graphics/core/ImageData.hpp"
+#include "util/platform.hpp"
+
+static debug::Logger logger("window-control");
+
+namespace {
+    static std::unique_ptr<ImageData> load_icon() {
+        try {
+            auto file = "res:textures/misc/icon.png";
+            if (io::exists(file)) {
+                return imageio::read(file);
+            }
+        } catch (const std::exception& err) {
+            logger.error() << "could not load window icon: " << err.what();
+        }
+        return nullptr;
+    }
+}
+
+WindowControl::WindowControl(Engine& engine) : engine(engine) {}
+
+WindowControl::Result WindowControl::initialize() {
+    const auto& project = engine.getProject();
+    auto& settings = engine.getSettings();
+
+    std::string title = project.title;
+    if (title.empty()) {
+        title = "VoxelCore v" +
+                        std::to_string(ENGINE_VERSION_MAJOR) + "." +
+                        std::to_string(ENGINE_VERSION_MINOR);
+    }
+    if (ENGINE_DEBUG_BUILD) {
+        title += " [debug]";
+    }
+    if (engine.getDebuggingServer()) {
+        title = "[debugging] " + title;
+    }
+
+    auto [window, input] = Window::initialize(&settings.display, title);
+    if (!window || !input){
+        throw initialize_error("could not initialize window");
+    }
+    window->setFramerate(settings.display.framerate.get());
+    if (auto icon = load_icon()) {
+        icon->flipY();
+        window->setIcon(icon.get());
+    }
+
+    return Result {std::move(window), std::move(input)};
+}
+
+void WindowControl::saveScreenshot() {
+    auto& window = engine.getWindow();
+    const auto& paths = engine.getPaths();
+
+    auto image = window.takeScreenshot();
+    image->flipY();
+    io::path filename = paths.getNewScreenshotFile("png");
+    imageio::write(filename.string(), image.get());
+    logger.info() << "saved screenshot as " << filename.string();
+}
+
+void WindowControl::toggleFullscreen() {
+    auto& settings = engine.getSettings();
+    auto& windowMode = settings.display.windowMode;
+    if (windowMode.get() != static_cast<int>(WindowMode::FULLSCREEN)) {
+        windowMode.set(static_cast<int>(WindowMode::FULLSCREEN));
+    } else {
+        windowMode.set(static_cast<int>(WindowMode::WINDOWED));
+    }
+}
+
+void WindowControl::nextFrame(bool waitForRefresh) {
+    const auto& settings = engine.getSettings();
+    auto& window = engine.getWindow();
+    auto& input = engine.getInput();
+    window.setFramerate(
+        window.isIconified() && settings.display.limitFpsIconified.get()
+            ? 20
+            : settings.display.framerate.get()
+    );
+    window.swapBuffers();
+    input.pollEvents(waitForRefresh && !window.checkShouldRefresh());
+}
diff --git a/src/engine/WindowControl.hpp b/src/engine/WindowControl.hpp
new file mode 100644
index 00000000..2bea138e
--- /dev/null
+++ b/src/engine/WindowControl.hpp
@@ -0,0 +1,26 @@
+#pragma once
+
+#include <memory>
+
+class Window;
+class Input;
+class Engine;
+
+class WindowControl {
+public:
+    struct Result {
+        std::unique_ptr<Window> window;
+        std::unique_ptr<Input> input;
+    };
+    WindowControl(Engine& engine);
+
+    Result initialize();
+
+    void nextFrame(bool waitForRefresh);
+
+    void saveScreenshot();
+
+    void toggleFullscreen();
+private:
+    Engine& engine;
+};
diff --git a/src/frontend/hud.cpp b/src/frontend/hud.cpp
index c8301d26..89789e29 100644
--- a/src/frontend/hud.cpp
+++ b/src/frontend/hud.cpp
@@ -756,3 +756,13 @@ void Hud::setAllowPause(bool flag) {
     }
     allowPause = flag;
 }
+
+bool Hud::isOpen(const std::string& layoutid) const {
+    for (const auto& element : elements) {
+        auto doc = element.getDocument();
+        if (doc && doc->getId() == layoutid) {
+            return true;
+        }
+    }
+    return false;
+}
diff --git a/src/frontend/hud.hpp b/src/frontend/hud.hpp
index c0c7d1ef..560382d3 100644
--- a/src/frontend/hud.hpp
+++ b/src/frontend/hud.hpp
@@ -213,6 +213,8 @@ public:
 
     void setAllowPause(bool flag);
 
+    bool isOpen(const std::string& layoutid) const;
+
     static bool showGeneratorMinimap;
 
     /// @brief Runtime updating debug visualization texture
diff --git a/src/frontend/menu.cpp b/src/frontend/menu.cpp
index e46888df..372264a5 100644
--- a/src/frontend/menu.cpp
+++ b/src/frontend/menu.cpp
@@ -11,7 +11,7 @@
 #include "graphics/ui/elements/Menu.hpp"
 #include "graphics/ui/gui_util.hpp"
 #include "interfaces/Task.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "locale.hpp"
 #include "logic/scripting/scripting.hpp"
 #include "screens/MenuScreen.hpp"
diff --git a/src/frontend/screens/LevelScreen.cpp b/src/frontend/screens/LevelScreen.cpp
index d398b3cc..f3694d85 100644
--- a/src/frontend/screens/LevelScreen.cpp
+++ b/src/frontend/screens/LevelScreen.cpp
@@ -6,6 +6,7 @@
 #include "core_defs.hpp"
 #include "debug/Logger.hpp"
 #include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "assets/Assets.hpp"
 #include "frontend/ContentGfxCache.hpp"
 #include "frontend/LevelFrontend.hpp"
diff --git a/src/frontend/screens/MenuScreen.cpp b/src/frontend/screens/MenuScreen.cpp
index c1339494..6472578d 100644
--- a/src/frontend/screens/MenuScreen.cpp
+++ b/src/frontend/screens/MenuScreen.cpp
@@ -12,9 +12,11 @@
 #include "window/Camera.hpp"
 #include "engine/Engine.hpp"
 
-MenuScreen::MenuScreen(Engine& engine) : Screen(engine) {
-    uicamera =
-        std::make_unique<Camera>(glm::vec3(), engine.getWindow().getSize().y);
+MenuScreen::MenuScreen(Engine& engine)
+    : Screen(engine),
+      uicamera(
+          std::make_unique<Camera>(glm::vec3(), engine.getWindow().getSize().y)
+      ) {
     uicamera->perspective = false;
     uicamera->near = -1.0f;
     uicamera->far = 1.0f;
@@ -24,7 +26,7 @@ MenuScreen::MenuScreen(Engine& engine) : Screen(engine) {
 MenuScreen::~MenuScreen() = default;
 
 void MenuScreen::onOpen() {
-    engine.getContentControl().resetContent();
+    engine.getContentControl().resetContent({});
     
     auto menu = engine.getGUI().getMenu();
     menu->reset();
diff --git a/src/graphics/render/Decorator.cpp b/src/graphics/render/Decorator.cpp
index 94b8ee13..8bbb2c9d 100644
--- a/src/graphics/render/Decorator.cpp
+++ b/src/graphics/render/Decorator.cpp
@@ -19,6 +19,7 @@
 #include "logic/LevelController.hpp"
 #include "util/stringutil.hpp"
 #include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "audio/audio.hpp"
 #include "maths/util.hpp"
diff --git a/src/graphics/ui/elements/Container.cpp b/src/graphics/ui/elements/Container.cpp
index b930d76a..8d45c2a1 100644
--- a/src/graphics/ui/elements/Container.cpp
+++ b/src/graphics/ui/elements/Container.cpp
@@ -2,6 +2,8 @@
 
 #include "graphics/core/DrawContext.hpp"
 #include "graphics/core/Batch2D.hpp"
+#include "window/Window.hpp"
+#include "../GUI.hpp"
 
 #include <algorithm>
 #include <utility>
@@ -77,6 +79,10 @@ void Container::act(float delta) {
             node->act(delta);
         }
     }
+    if (!intervalEvents.empty()) {
+        // TODO: make it interval-based
+        gui.getWindow().setShouldRefresh();
+    }
     for (IntervalEvent& event : intervalEvents) {
         event.timer += delta;
         if (event.timer > event.interval) {
@@ -87,9 +93,10 @@ void Container::act(float delta) {
             }
         }
     }
+    GUI& gui = this->gui;
     intervalEvents.erase(std::remove_if(
         intervalEvents.begin(), intervalEvents.end(),
-        [](const IntervalEvent& event) {
+        [&gui](const IntervalEvent& event) {
             return event.repeat == 0;
         }
     ), intervalEvents.end());
diff --git a/src/io/settings_io.cpp b/src/io/settings_io.cpp
index 5e1c8327..f4e89338 100644
--- a/src/io/settings_io.cpp
+++ b/src/io/settings_io.cpp
@@ -51,6 +51,7 @@ SettingsHandler::SettingsHandler(EngineSettings& settings) {
     builder.add("framerate", &settings.display.framerate);
     builder.add("limit-fps-iconified", &settings.display.limitFpsIconified);
     builder.add("window-mode", &settings.display.windowMode);
+    builder.add("adaptive-menu-fps", &settings.display.adaptiveFpsInMenu);
 
     builder.section("camera");
     builder.add("sensitivity", &settings.camera.sensitivity);
diff --git a/src/logic/EngineController.cpp b/src/logic/EngineController.cpp
index 0d0a5a60..d6820fa1 100644
--- a/src/logic/EngineController.cpp
+++ b/src/logic/EngineController.cpp
@@ -4,28 +4,29 @@
 #include <algorithm>
 #include <memory>
 
-#include "engine/Engine.hpp"
 #include "coders/commons.hpp"
-#include "debug/Logger.hpp"
 #include "coders/json.hpp"
-#include "content/ContentReport.hpp"
 #include "content/ContentControl.hpp"
+#include "content/ContentReport.hpp"
 #include "content/PacksManager.hpp"
-#include "world/files/WorldConverter.hpp"
-#include "world/files/WorldFiles.hpp"
+#include "debug/Logger.hpp"
+#include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "frontend/locale.hpp"
 #include "frontend/menu.hpp"
 #include "frontend/screens/LevelScreen.hpp"
 #include "frontend/screens/MenuScreen.hpp"
-#include "graphics/ui/GUI.hpp"
 #include "graphics/ui/elements/Menu.hpp"
 #include "graphics/ui/gui_util.hpp"
-#include "objects/Players.hpp"
+#include "graphics/ui/GUI.hpp"
 #include "interfaces/Task.hpp"
+#include "LevelController.hpp"
+#include "objects/Players.hpp"
 #include "util/stringutil.hpp"
+#include "world/files/WorldConverter.hpp"
+#include "world/files/WorldFiles.hpp"
 #include "world/Level.hpp"
 #include "world/World.hpp"
-#include "LevelController.hpp"
 
 static debug::Logger logger("engine-control");
 
diff --git a/src/logic/scripting/lua/libs/libaudio.cpp b/src/logic/scripting/lua/libs/libaudio.cpp
index 7ec6f1a6..b80676c1 100644
--- a/src/logic/scripting/lua/libs/libaudio.cpp
+++ b/src/logic/scripting/lua/libs/libaudio.cpp
@@ -1,6 +1,7 @@
 #include "audio/audio.hpp"
 #include "assets/Assets.hpp"
 #include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "api_lua.hpp"
 
 inline const char* DEFAULT_CHANNEL = "regular";
diff --git a/src/logic/scripting/lua/libs/libcore.cpp b/src/logic/scripting/lua/libs/libcore.cpp
index 9f14e2a0..8f8a7bc8 100644
--- a/src/logic/scripting/lua/libs/libcore.cpp
+++ b/src/logic/scripting/lua/libs/libcore.cpp
@@ -8,7 +8,7 @@
 #include "content/Content.hpp"
 #include "content/ContentControl.hpp"
 #include "engine/Engine.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "io/settings_io.hpp"
 #include "frontend/menu.hpp"
@@ -43,7 +43,16 @@ static int l_reset_content(lua::State* L) {
     if (level != nullptr) {
         throw std::runtime_error("world must be closed before");
     }
-    content_control->resetContent();
+    std::vector<std::string> nonResetPacks;
+    if (lua::istable(L, 1)) {
+        int len = lua::objlen(L, 1);
+        for (int i = 0; i < len; i++) {
+            lua::rawgeti(L, i + 1, 1);
+            nonResetPacks.emplace_back(lua::require_lstring(L, -1));
+            lua::pop(L);
+        }
+    }
+    content_control->resetContent(std::move(nonResetPacks));
     return 0;
 }
 
diff --git a/src/logic/scripting/lua/libs/libentity.cpp b/src/logic/scripting/lua/libs/libentity.cpp
index 26d3ea61..3b9730c2 100644
--- a/src/logic/scripting/lua/libs/libentity.cpp
+++ b/src/logic/scripting/lua/libs/libentity.cpp
@@ -2,6 +2,7 @@
 
 #include "content/Content.hpp"
 #include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "objects/Entities.hpp"
 #include "objects/EntityDef.hpp"
 #include "objects/Entity.hpp"
diff --git a/src/logic/scripting/lua/libs/libfile.cpp b/src/logic/scripting/lua/libs/libfile.cpp
index 28ed5a6e..c3ee4bdb 100644
--- a/src/logic/scripting/lua/libs/libfile.cpp
+++ b/src/logic/scripting/lua/libs/libfile.cpp
@@ -3,7 +3,7 @@
 
 #include "coders/gzip.hpp"
 #include "engine/Engine.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "io/devices/ZipFileDevice.hpp"
 #include "util/stringutil.hpp"
diff --git a/src/logic/scripting/lua/libs/libgeneration.cpp b/src/logic/scripting/lua/libs/libgeneration.cpp
index ec10c294..2e872ec7 100644
--- a/src/logic/scripting/lua/libs/libgeneration.cpp
+++ b/src/logic/scripting/lua/libs/libgeneration.cpp
@@ -9,6 +9,7 @@
 #include "content/Content.hpp"
 #include "content/ContentControl.hpp"
 #include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "../usertypes/lua_type_voxelfragment.hpp"
 
 using namespace scripting;
diff --git a/src/logic/scripting/lua/libs/libhud.cpp b/src/logic/scripting/lua/libs/libhud.cpp
index e3d29783..7ab5d33c 100644
--- a/src/logic/scripting/lua/libs/libhud.cpp
+++ b/src/logic/scripting/lua/libs/libhud.cpp
@@ -189,6 +189,11 @@ static int l_reload_script(lua::State* L) {
     return 0;
 }
 
+static int l_is_open(lua::State* L) {
+    auto layoutid = lua::require_string(L, 1);
+    return lua::pushboolean(L, hud->isOpen(layoutid));
+}
+
 const luaL_Reg hudlib[] = {
     {"open_inventory", wrap_hud<l_open_inventory>},
     {"close_inventory", wrap_hud<l_close_inventory>},
@@ -208,5 +213,6 @@ const luaL_Reg hudlib[] = {
     {"_set_debug_cheats", wrap_hud<l_set_debug_cheats>},
     {"set_allow_pause", wrap_hud<l_set_allow_pause>},
     {"reload_script", wrap_hud<l_reload_script>},
+    {"is_open", wrap_hud<l_is_open>},
     {nullptr, nullptr}
 };
diff --git a/src/logic/scripting/lua/libs/libpack.cpp b/src/logic/scripting/lua/libs/libpack.cpp
index f23e96b3..b7162b4d 100644
--- a/src/logic/scripting/lua/libs/libpack.cpp
+++ b/src/logic/scripting/lua/libs/libpack.cpp
@@ -10,7 +10,7 @@
 #include "graphics/ui/elements/Menu.hpp"
 #include "frontend/locale.hpp"
 #include "world/files/WorldFiles.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "world/Level.hpp"
 #include "world/World.hpp"
 #include "api_lua.hpp"
diff --git a/src/logic/scripting/lua/libs/libworld.cpp b/src/logic/scripting/lua/libs/libworld.cpp
index 41778204..eb966f50 100644
--- a/src/logic/scripting/lua/libs/libworld.cpp
+++ b/src/logic/scripting/lua/libs/libworld.cpp
@@ -10,7 +10,7 @@
 #include "content/ContentControl.hpp"
 #include "engine/Engine.hpp"
 #include "world/files/WorldFiles.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "lighting/Lighting.hpp"
 #include "voxels/Chunk.hpp"
diff --git a/src/logic/scripting/lua/lua_engine.cpp b/src/logic/scripting/lua/lua_engine.cpp
index 80e2cff7..eef391b5 100644
--- a/src/logic/scripting/lua/lua_engine.cpp
+++ b/src/logic/scripting/lua/lua_engine.cpp
@@ -4,7 +4,7 @@
 #include <iostream>
 
 #include "io/io.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "debug/Logger.hpp"
 #include "util/stringutil.hpp"
 #include "libs/api_lua.hpp"
diff --git a/src/logic/scripting/lua/lua_util.cpp b/src/logic/scripting/lua/lua_util.cpp
index a09f5086..6fdbe91e 100644
--- a/src/logic/scripting/lua/lua_util.cpp
+++ b/src/logic/scripting/lua/lua_util.cpp
@@ -336,6 +336,22 @@ int lua::create_environment(State* L, int parent) {
     return id;
 }
 
+int lua::restore_pack_environment(lua::State* L, const std::string& packid) {
+    if(!lua::getglobal(L, "__vc__pack_envs")) {
+        return -1;
+    }
+    int id = nextEnvironment++;
+
+    if (lua::getfield(L, packid)) {
+        // envname = env
+        setglobal(L, env_name(id));
+        lua::pop(L);
+        return id;
+    }
+    lua::pop(L);
+    return -1;
+}
+
 void lua::remove_environment(State* L, int id) {
     if (id == 0) {
         return;
diff --git a/src/logic/scripting/lua/lua_util.hpp b/src/logic/scripting/lua/lua_util.hpp
index 29f25f34..f64cdbf7 100644
--- a/src/logic/scripting/lua/lua_util.hpp
+++ b/src/logic/scripting/lua/lua_util.hpp
@@ -613,6 +613,7 @@ namespace lua {
         return 0;
     }
     int create_environment(lua::State*, int parent);
+    int restore_pack_environment(lua::State*, const std::string& packid);
     void remove_environment(lua::State*, int id);
 
     inline void close(lua::State* L) {
diff --git a/src/logic/scripting/lua/usertypes/lua_type_heightmap.cpp b/src/logic/scripting/lua/usertypes/lua_type_heightmap.cpp
index 9f9d2ed8..d6528298 100644
--- a/src/logic/scripting/lua/usertypes/lua_type_heightmap.cpp
+++ b/src/logic/scripting/lua/usertypes/lua_type_heightmap.cpp
@@ -8,6 +8,7 @@
 #include "graphics/core/ImageData.hpp"
 #include "maths/Heightmap.hpp"
 #include "engine/Engine.hpp"
+#include "engine/EnginePaths.hpp"
 #include "../lua_util.hpp"
 #include "lua_type_heightmap.hpp"
 
diff --git a/src/logic/scripting/scripting.cpp b/src/logic/scripting/scripting.cpp
index 244975c3..19accc89 100644
--- a/src/logic/scripting/scripting.cpp
+++ b/src/logic/scripting/scripting.cpp
@@ -9,7 +9,7 @@
 #include "content/ContentControl.hpp"
 #include "debug/Logger.hpp"
 #include "engine/Engine.hpp"
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "io/io.hpp"
 #include "frontend/UiDocument.hpp"
 #include "items/Inventory.hpp"
@@ -172,7 +172,15 @@ std::unique_ptr<Process> scripting::start_app_script(const io::path& script) {
     const ContentPack& pack
 ) {
     auto L = lua::get_main_state();
-    int id = lua::create_environment(L, 0);
+    int id = lua::restore_pack_environment(L, pack.id);
+    if (id != -1) {
+        return std::shared_ptr<int>(new int(id), [=](int* id) { //-V508
+            lua::remove_environment(L, *id);
+            delete id;
+        });
+    }
+    id = lua::create_environment(L, 0);
+
     lua::pushenv(L, id);
     lua::pushvalue(L, -1);
     lua::setfield(L, "PACK_ENV");
@@ -347,7 +355,7 @@ void scripting::on_world_quit() {
     scripting::controller = nullptr;
 }
 
-void scripting::cleanup() {
+void scripting::cleanup(const std::vector<std::string>& nonReset) {
     auto L = lua::get_main_state();
     lua::requireglobal(L, "pack");
     for (auto& pack : content_control->getAllContentPacks()) {
@@ -358,7 +366,12 @@ void scripting::cleanup() {
     lua::pop(L);
 
     if (lua::getglobal(L, "__scripts_cleanup")) {
-        lua::call_nothrow(L, 0);
+        lua::createtable(L, nonReset.size(), 0);
+        for (size_t i = 0; i < nonReset.size(); i++) {
+            lua::pushstring(L, nonReset[i]);
+            lua::rawseti(L, i + 1);
+        }
+        lua::call_nothrow(L, 1);
     }
 }
 
diff --git a/src/logic/scripting/scripting.hpp b/src/logic/scripting/scripting.hpp
index d9c7e614..a096e9cc 100644
--- a/src/logic/scripting/scripting.hpp
+++ b/src/logic/scripting/scripting.hpp
@@ -82,7 +82,7 @@ namespace scripting {
     void on_world_tick(int tps);
     void on_world_save();
     void on_world_quit();
-    void cleanup();
+    void cleanup(const std::vector<std::string>& nonReset);
     void on_blocks_tick(const Block& block, int tps);
     void update_block(const Block& block, const glm::ivec3& pos);
     void random_update_block(const Block& block, const glm::ivec3& pos);
diff --git a/src/settings.hpp b/src/settings.hpp
index f97fb513..ee35d5a4 100644
--- a/src/settings.hpp
+++ b/src/settings.hpp
@@ -31,6 +31,8 @@ struct DisplaySettings {
     IntegerSetting framerate {-1, -1, 120};
     /// @brief Limit framerate when window is iconified
     FlagSetting limitFpsIconified {false};
+    /// @brief Adaptive framerate in menu (experimental)
+    FlagSetting adaptiveFpsInMenu {false};
 };
 
 struct ChunksSettings {
diff --git a/src/util/command_line.cpp b/src/util/command_line.cpp
index 3691b77b..7cb3614e 100644
--- a/src/util/command_line.cpp
+++ b/src/util/command_line.cpp
@@ -6,7 +6,7 @@
 #include <string>
 #include <iomanip>
 
-#include "io/engine_paths.hpp"
+#include "engine/EnginePaths.hpp"
 #include "util/ArgsReader.hpp"
 #include "engine/Engine.hpp"
 
diff --git a/src/window/Window.hpp b/src/window/Window.hpp
index 135e4f7d..71004470 100644
--- a/src/window/Window.hpp
+++ b/src/window/Window.hpp
@@ -18,6 +18,8 @@ enum class WindowMode {
 
 class Window {
 public:
+    static inline constexpr int FPS_UNLIMITED = 0;
+
     Window(glm::ivec2 size) : size(std::move(size)) {}
 
     virtual ~Window() = default;
@@ -40,6 +42,9 @@ public:
     virtual void popScissor() = 0;
     virtual void resetScissor() = 0;
 
+    virtual void setShouldRefresh() = 0;
+    virtual bool checkShouldRefresh() = 0;
+
     virtual double time() = 0;
 
     virtual void setFramerate(int framerate) = 0;
diff --git a/src/window/detail/GLFWWindow.cpp b/src/window/detail/GLFWWindow.cpp
index 27f56d3c..a80c10e0 100644
--- a/src/window/detail/GLFWWindow.cpp
+++ b/src/window/detail/GLFWWindow.cpp
@@ -180,14 +180,18 @@ public:
         : window(window) {
     }
 
-    void pollEvents() override {
+    void pollEvents(bool waitForRefresh) override {
         delta.x = 0.0f;
         delta.y = 0.0f;
         scroll = 0;
         currentFrame++;
         codepoints.clear();
         pressedKeys.clear();
-        glfwPollEvents();
+        if (waitForRefresh) {
+            glfwWaitEvents();
+        } else {
+            glfwPollEvents();
+        }
 
         for (auto& [_, binding] : bindings.getAll()) {
             if (!binding.enabled) {
@@ -377,6 +381,18 @@ public:
         prevSwap = time();
     }
 
+    void setShouldRefresh() override {
+        shouldRefresh = true;
+    }
+
+    bool checkShouldRefresh() override {
+        if (shouldRefresh) {
+            shouldRefresh = false;
+            return true;
+        }
+        return false;
+    }
+
     bool isMaximized() const override {
         return glfwGetWindowAttrib(window, GLFW_MAXIMIZED);
     }
@@ -557,12 +573,14 @@ private:
     double prevSwap = 0.0;
     int posX = 0;
     int posY = 0;
+    bool shouldRefresh = true;
 };
 static_assert(!std::is_abstract<GLFWWindow>());
 
 static void mouse_button_callback(GLFWwindow* window, int button, int action, int) {
     auto handler = static_cast<GLFWWindow*>(glfwGetWindowUserPointer(window));
     handler->input.onMouseCallback(button, action == GLFW_PRESS);
+    handler->setShouldRefresh();
 }
 
 static void character_callback(GLFWwindow* window, unsigned int codepoint) {
@@ -574,6 +592,8 @@ static void key_callback(
     GLFWwindow* window, int key, int /*scancode*/, int action, int /*mode*/
 ) {
     auto handler = static_cast<GLFWWindow*>(glfwGetWindowUserPointer(window));
+    handler->setShouldRefresh();
+
     auto& input = handler->input;
     if (key == GLFW_KEY_UNKNOWN) {
         return;
@@ -599,11 +619,13 @@ static void window_size_callback(GLFWwindow* window, int width, int height) {
 static void scroll_callback(GLFWwindow* window, double, double yoffset) {
     auto handler = static_cast<GLFWWindow*>(glfwGetWindowUserPointer(window));
     handler->input.scroll += yoffset;
+    handler->setShouldRefresh();
 }
 
 static void cursor_pos_callback(GLFWwindow* window, double xpos, double ypos) {
     auto handler = static_cast<GLFWWindow*>(glfwGetWindowUserPointer(window));
     handler->input.setCursorPosition(xpos, ypos);
+    handler->setShouldRefresh();
 }
 
 static void iconify_callback(GLFWwindow* window, int iconified) {
@@ -629,6 +651,11 @@ static void create_standard_cursors() {
     }
 }
 
+static void refresh_callback(GLFWwindow* window) {
+    auto handler = static_cast<GLFWWindow*>(glfwGetWindowUserPointer(window));
+    handler->setShouldRefresh();
+}
+
 static void setup_callbacks(GLFWwindow* window) {
     glfwSetKeyCallback(window, key_callback);
     glfwSetMouseButtonCallback(window, mouse_button_callback);
@@ -637,6 +664,7 @@ static void setup_callbacks(GLFWwindow* window) {
     glfwSetCharCallback(window, character_callback);
     glfwSetScrollCallback(window, scroll_callback);
     glfwSetWindowIconifyCallback(window, iconify_callback);
+    glfwSetWindowRefreshCallback(window, refresh_callback);
 }
 
 std::tuple<
diff --git a/src/window/input.hpp b/src/window/input.hpp
index 2edfe4c7..84c12040 100644
--- a/src/window/input.hpp
+++ b/src/window/input.hpp
@@ -261,7 +261,7 @@ class Input {
 public:
     virtual ~Input() = default;
 
-    virtual void pollEvents() = 0;
+    virtual void pollEvents(bool waitForRefresh) = 0;
 
     virtual const char* getClipboardText() const = 0;
     virtual void setClipboardText(const char* str) = 0;