diff --git a/doc/en/block-properties.md b/doc/en/block-properties.md
index f3137dd60..d98a8cac5 100644
--- a/doc/en/block-properties.md
+++ b/doc/en/block-properties.md
@@ -1,6 +1,6 @@
 # Block properties
 
-## Visual
+## Visual & Audio
 
 ### *texture*
 
@@ -70,6 +70,18 @@ Rotation profile (set of available block rotations and behaviour of placing bloc
 - "pane" - panels, doors, signs
 - "stairs" - "pane" + flipped variants
 
+### *particles*
+
+Particles are specified as a JSON object. Property names can be found [in the particles section](particles.md).
+
+When camera is near to the block, the engine will create an emitter that will run
+until the block is destroyed or the camera moves away a certain distance.
+
+### Material - *material*
+
+Defines the name of the block's material in the format `pack:material_name`, which affects the selection of block interaction sounds.
+Material definitions are located in /block_materials.
+
 ## Variants
 
 Some properties can vary dynamically, depending on the variant number stored in the user bits of the block.
diff --git a/doc/en/entity-properties.md b/doc/en/entity-properties.md
index 8bc4d5d37..b0aee9aea 100644
--- a/doc/en/entity-properties.md
+++ b/doc/en/entity-properties.md
@@ -61,12 +61,16 @@ Determines how the physics engine will work with it.
 
 ### *blocking*
 
-Determines whether the entity blocks installation of blocks.
+If true - the entity blocks the placement of a block that intersects with the entity's hitbox.
 
 *In the future will also block other entities movement.*
 
 Default value: *true*.
 
+### *selectable*
+
+If set to `false` the cursor will ignore the entity, passing the ray.
+
 ### *sensors*
 
 A sensor is an area attached to a physical body that detects the entry of other bodies into it.
diff --git a/doc/en/rigging.md b/doc/en/rigging.md
index 4b69b5769..abb5ad81a 100644
--- a/doc/en/rigging.md
+++ b/doc/en/rigging.md
@@ -38,7 +38,7 @@ Models are loaded automatically; adding them to preload.json is not required.
 
 ## Models
 
-Models should be located in the models folder. Currently only OBJ format is supported.
+Models must be located in the models folder. Currently, the following formats are supported: obj, vec3, and [vcm](vcm.md).
 
 >[!IMPORTANT]
 > When loading an obj model, the \*.mtl file is ignored.
diff --git a/doc/en/scripting/builtins/libapp.md b/doc/en/scripting/builtins/libapp.md
index 0ec755689..48d79bf8e 100644
--- a/doc/en/scripting/builtins/libapp.md
+++ b/doc/en/scripting/builtins/libapp.md
@@ -180,14 +180,34 @@ app.get_content_sources() -> table<string>
 
 Returns a list of content sources (paths), in descending priority order.
 
-``lua
+```lua
 app.set_content_sources(sources: table<string>)
 ```
 
 Sets a list of content sources (paths). Specified in descending priority order.
 
-``lua
+```lua
 app.reset_content_sources()
 ```
 
 Resets content sources.
+
+## Sub-instances
+
+```lua
+-- Creates a headless engine instance with the current project and the specified application script.
+-- Returns the instance ID. The number of active sub-instances is currently limited to one.
+app.start_background_instance(
+    -- script file
+    app_script: string,
+    -- log file
+    output_file: string | nil
+) -> int
+
+-- Checks if the engine sub-instance is alive.
+app.is_instance_alive(handle: int) -> boolean
+
+-- Stops the engine sub-instance.
+-- Returns true if the instance was alive at the time of the call.
+app.terminate(handle: int) -> boolean
+```
diff --git a/doc/en/scripting/builtins/libblock.md b/doc/en/scripting/builtins/libblock.md
index 4513d57cf..cc69e47d8 100644
--- a/doc/en/scripting/builtins/libblock.md
+++ b/doc/en/scripting/builtins/libblock.md
@@ -28,7 +28,8 @@ block.get(x: int, y: int, z: int) -> int
 block.get_states(x: int, y: int, z: int) -> int
 
 -- Set block with given integer ID and state (default - 0) at given position.
-block.set(x: int, y: int, z: int, id: int, states: int)
+-- If noupdate=true is passed, the `on_update` event will not be called for adjacent blocks.
+block.set(x: int, y: int, z: int, id: int, states: int, noupdate: boolean=false)
 
 -- Places a block with a given integer id and state (default - 0) at given position.
 -- on behalf of the player, calling the on_placed event.
diff --git a/doc/en/scripting/builtins/libworld.md b/doc/en/scripting/builtins/libworld.md
index 54b44fe15..72bfaf8e4 100644
--- a/doc/en/scripting/builtins/libworld.md
+++ b/doc/en/scripting/builtins/libworld.md
@@ -92,6 +92,8 @@ world.raycast(
         -- exclusion filtering mode:
         --   if true, filter_entities defines the list of ignored entity types
         entities_exclusion: bool = false,
+        -- include entities with selectable=false
+        nonselect_entities: bool = false;
 
         [==[ additional parameters (blocks) ]==]
         -- id of the block types used for filtering
diff --git a/doc/ru/block-properties.md b/doc/ru/block-properties.md
index 50bd7f023..e139f635d 100644
--- a/doc/ru/block-properties.md
+++ b/doc/ru/block-properties.md
@@ -1,6 +1,6 @@
 # Свойства блоков
 
-## Вид
+## Вид & Звук
 
 ### Текстура - *texture*
 
@@ -78,6 +78,11 @@
 При приближении к блоку движок создаст эмиттер, который будет работать 
 до разрушения блока или отдаления камеры на некоторое расстояние.
 
+### Материал - *material*
+
+Определяет имя материала блока в формате `пак:имя_материала`, что влияет на выбор звуков взаимодействия с блоком.
+Определения материалов расположены в /block_materials.
+
 ## Варианты
 
 Некоторые свойства могут варьироваться динамически, в зависимости от номера варианта, хранимого в пользовательских битах блока.
diff --git a/doc/ru/entity-properties.md b/doc/ru/entity-properties.md
index de10cfd32..2f5ca3791 100644
--- a/doc/ru/entity-properties.md
+++ b/doc/ru/entity-properties.md
@@ -61,12 +61,16 @@
 
 ### Блокирование - *blocking*
 
-Определяет блокирует ли сущность установку блоков.
+Определяет, блокирует ли сущность установку блока, пересекающегося с хитбоксом сущности.
 
 *В будущем будет также блокировать движение других сущностей.*
 
 Значение по-умолчанию: *true*.
 
+### Выделяемость - *selectable*
+
+При значении в `false` курсор будет игнорировать cущность, пропуская луч далее.
+
 ### Список сенсоров - *sensors*
 
 Сенсор - область пространства, привязанная к физическому телу, детектирующее попадание в него других тел.
diff --git a/doc/ru/rigging.md b/doc/ru/rigging.md
index 86ec0a09b..388b19ea2 100644
--- a/doc/ru/rigging.md
+++ b/doc/ru/rigging.md
@@ -38,7 +38,7 @@
 
 ## Модели
 
-Модели должны располагаться в папке models. На данный момент поддерживается только OBJ формат.
+Модели должны располагаться в папке models. На данный момент поддерживаются форматы: obj, vec3 и [vcm](vcm.md).
 
 >[!IMPORTANT]
 > При загрузке obj модели игнорируется файл \*.mtl. 
diff --git a/doc/ru/scripting/builtins/libapp.md b/doc/ru/scripting/builtins/libapp.md
index 07e358ef4..bbdf5cd2f 100644
--- a/doc/ru/scripting/builtins/libapp.md
+++ b/doc/ru/scripting/builtins/libapp.md
@@ -142,4 +142,24 @@ app.set_content_sources(sources: table<string>)
 
 -- Сбрасывает список источников контента.
 app.reset_content_sources()
-```
\ No newline at end of file
+```
+
+## Под-экземпляры
+
+```lua
+-- Создаёт headless-экземпляр движка с текущим проектом и указанным сценарием.
+-- Возвращает id экземпляра. Число живых под-экземпляров, на данный момент, ограничено одним.
+app.start_background_instance(
+    -- файл сценария
+    app_script: string,
+    -- файл лога
+    output_file: string | nil
+) -> int
+
+-- Проверяет, жив ли под-экземпляр движка.
+app.is_instance_alive(handle: int) -> boolean
+
+-- Останавливает под-экземпляр движка.
+-- Возвращает true если экземпляр был жив в момент вызова.
+app.terminate_instance(handle: int) -> boolean
+```
diff --git a/doc/ru/scripting/builtins/libworld.md b/doc/ru/scripting/builtins/libworld.md
index 6b945aa76..52812f295 100644
--- a/doc/ru/scripting/builtins/libworld.md
+++ b/doc/ru/scripting/builtins/libworld.md
@@ -91,6 +91,8 @@ world.raycast(
         -- исключающий режим фильтрации:
         --   при значении (true) filter_entities определяет список игнорируемых
         entities_exclusion: bool = false,
+        -- учитывать сущности с selectable=false
+        nonselect_entities: bool = false;
         
         [==[ дополнительные параметры (блоки) ]==]
         -- id типов блоков используемых для фильтрации
diff --git a/res/content/base/config/defaults.toml b/res/content/base/config/defaults.toml
index 650c24d74..d2c5142cc 100644
--- a/res/content/base/config/defaults.toml
+++ b/res/content/base/config/defaults.toml
@@ -1,3 +1,4 @@
 generator = "base:demo"
 player-entity = "base:player"
 hand-skeleton = "base:hand"
+block-material = "base:stone"
diff --git a/res/content/base/scripts/components/drop.lua b/res/content/base/scripts/components/drop.lua
index 39bd03ceb..335b81d89 100644
--- a/res/content/base/scripts/components/drop.lua
+++ b/res/content/base/scripts/components/drop.lua
@@ -10,7 +10,7 @@ dropitem = ARGS
 if dropitem.item then
     dropitem.id = item.index(dropitem.item)
 end
-if dropitem then 
+if dropitem then
     timer = dropitem.pickup_delay or timer
 end
 if SAVED_DATA.item then
@@ -26,6 +26,7 @@ function on_save()
 end
 
 if vc.is_client() then
+    local SCALE = 0.3
     local scale = {1, 1, 1}
     local rotation = mat4.rotate({
         math.random(), math.random(), math.random()
@@ -35,7 +36,7 @@ if vc.is_client() then
         local matrix = mat4.idt()
         rig:set_model(0, item.model_name(dropitem.id))
         local bodysize = math.min(scale[1], scale[2], scale[3])
-        body:set_size({scale[1], bodysize, scale[3]})
+        body:set_size(vec3.mul({scale[1], bodysize, scale[3]}, SCALE))
         mat4.mul(matrix, rotation, matrix)
         mat4.scale(matrix, scale, matrix)
         rig:set_matrix(0, matrix)
diff --git a/res/layouts/pages/content.xml.lua b/res/layouts/pages/content.xml.lua
index 2937542f4..cb63a96c7 100644
--- a/res/layouts/pages/content.xml.lua
+++ b/res/layouts/pages/content.xml.lua
@@ -3,6 +3,7 @@ function on_open(params)
         mode = params.mode
     end
     refresh()
+    document.search_textbox.focused = true
 end
 
 -- add - packs to be added to the world (after apply)
diff --git a/res/modules/internal/rules.lua b/res/modules/internal/rules.lua
index a1a5a8c32..4d739cf35 100644
--- a/res/modules/internal/rules.lua
+++ b/res/modules/internal/rules.lua
@@ -1,4 +1,4 @@
-local rules = {nexid = 1, rules = {}}
+local rules = {nextid = 1, rules = {}}
 
 function rules.get_rule(name)
     local rule = rules.rules[name]
@@ -27,13 +27,13 @@ end
 
 function rules.reset(name)
     local rule = rules.get_rule(name)
-    rules.set(rule.default)
+    rules.set(name, rule.default)
 end
 
 function rules.listen(name, handler)
     local rule = rules.get_rule(name)
-    local id = rules.nexid
-    rules.nextid = rules.nexid + 1
+    local id = rules.nextid
+    rules.nextid = rules.nextid + 1
     rule.listeners[utf8.encode(id)] = handler
     return id
 end
diff --git a/res/project.toml b/res/project.toml
index b641ad00f..281964857 100644
--- a/res/project.toml
+++ b/res/project.toml
@@ -3,5 +3,6 @@ name = "default"
 base_packs = ["base"]
 permissions = [
     "network",
-    "record-audio"
+    "record-audio",
+    "sub-instances",
 ]
diff --git a/res/scripts/stdcmd.lua b/res/scripts/stdcmd.lua
index c2b102675..03df9235f 100644
--- a/res/scripts/stdcmd.lua
+++ b/res/scripts/stdcmd.lua
@@ -140,7 +140,7 @@ console.add_command(
         for y=y1,y2 do
             for z=z1,z2 do
                 for x=x1,x2 do
-                    block.set(x, y, z, id)
+                    block.set(x, y, z, id, 0, true)
                 end
             end
         end
diff --git a/res/scripts/stdlib.lua b/res/scripts/stdlib.lua
index 9793216a2..2869bba1c 100644
--- a/res/scripts/stdlib.lua
+++ b/res/scripts/stdlib.lua
@@ -140,7 +140,20 @@ local __vc_named_coroutines = {}
 local __vc_next_coroutine = 1
 
 function __vc_start_coroutine(chunk)
-    local co = coroutine.create(chunk)
+    local co = coroutine.create(function()
+        local _, err = xpcall(chunk, function(msg)
+            local traceback = debug.get_traceback(0)
+            local s = string.format("%s:", msg)
+            for i=1,#traceback - 2 do
+                local frame = traceback[i]
+                s = s .. "\n\t"..tb_frame_tostring(frame)
+            end
+            return s
+        end)
+        if err then
+            error(err)
+        end
+    end)
     local id = __vc_next_coroutine
     __vc_next_coroutine = __vc_next_coroutine + 1
     __vc_coroutines[id] = co
diff --git a/res/scripts/stdmin.lua b/res/scripts/stdmin.lua
index 2868dd634..e341f68a1 100644
--- a/res/scripts/stdmin.lua
+++ b/res/scripts/stdmin.lua
@@ -10,8 +10,9 @@ vc = {
     is_client = function()
         return not _vc_headless
     end,
+    get_version = __vc_app.get_version,
     get_setting = __vc_app.get_setting,
-    get_setting_str = __vc_app.get_setting_str,
+    str_setting = __vc_app.str_setting,
     get_setting_info = __vc_app.get_setting_info,
 }
 
diff --git a/src/constants.hpp b/src/constants.hpp
index f43314f4a..5bacfe078 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -16,6 +16,9 @@ inline constexpr bool ENGINE_DEBUG_BUILD = true;
 
 inline const std::string ENGINE_VERSION_STRING = "0.32";
 
+inline constexpr uint MAX_SUBPROCESSES = 1;
+inline constexpr uint MAX_SUBPROCESS_DEPTH = 2;
+
 /// @brief world regions format version
 inline constexpr uint REGION_FORMAT_VERSION = 3;
 
diff --git a/src/content/ContentBuilder.cpp b/src/content/ContentBuilder.cpp
index ce77434ed..97498b497 100644
--- a/src/content/ContentBuilder.cpp
+++ b/src/content/ContentBuilder.cpp
@@ -26,17 +26,21 @@ std::unique_ptr<Content> ContentBuilder::build() {
             def.rt.tags.insert(tags.add(tag));
         }
 
+        auto isSolid = [](const Variant& variant) {
+            return variant.model.type == BlockModelType::BLOCK ||
+                   variant.culling == CullingMode::OPTIONAL;
+        };
+
         if (def.variants) {
             for (auto& variant : def.variants->variants) {
-                variant.rt.solid =
-                    variant.model.type == BlockModelType::BLOCK ||
-                    def.explictlySolid;
+                variant.rt.solid = isSolid(variant) || def.explictlySolid;
             }
             def.defaults = def.variants->variants.at(0);
         } else {
-            def.defaults.rt.solid =
-                def.defaults.model.type == BlockModelType::BLOCK ||
-                def.explictlySolid;
+            def.defaults.rt.solid = isSolid(def.defaults) || def.explictlySolid;
+        }
+        if (def.material.empty()) {
+            defaults.at("block-material").get(def.material);
         }
 
         const float EPSILON = 0.01f;
diff --git a/src/content/loading/EntityLoader.cpp b/src/content/loading/EntityLoader.cpp
index 5741b2079..e785fb0fe 100644
--- a/src/content/loading/EntityLoader.cpp
+++ b/src/content/loading/EntityLoader.cpp
@@ -89,6 +89,7 @@ template<> void ContentUnitLoader<EntityDef>::loadUnit(
     root.at("skeleton-name").get(def.skeletonName);
     root.at("material").get(def.material);
     root.at("blocking").get(def.blocking);
+    root.at("selectable").get(def.selectable);
     root.at("solid").get(def.solid);
     root.at("mass").get(def.mass);
     root.at("elasticity").get(def.elasticity);
diff --git a/src/devtools/AppScriptsControl.cpp b/src/devtools/AppScriptsControl.cpp
index bb1a386a2..f565949aa 100644
--- a/src/devtools/AppScriptsControl.cpp
+++ b/src/devtools/AppScriptsControl.cpp
@@ -8,11 +8,7 @@
 
 static debug::Logger logger("app-scripts");
 
-AppScriptsControl::AppScriptsControl(
-    const CoreParameters& params, const Project& project
-)
-    : project(project) {
-
+AppScriptsControl::AppScriptsControl(const CoreParameters& params) {
     io::path scriptFile =
         params.scriptFile.empty()
             ? "project:start.lua"
diff --git a/src/devtools/AppScriptsControl.hpp b/src/devtools/AppScriptsControl.hpp
index 4e44eef60..3531dc2f9 100644
--- a/src/devtools/AppScriptsControl.hpp
+++ b/src/devtools/AppScriptsControl.hpp
@@ -14,7 +14,7 @@ struct Project;
 
 class AppScriptsControl {
 public:
-    AppScriptsControl(const CoreParameters& params, const Project& project);
+    AppScriptsControl(const CoreParameters& params);
 
     void tick();
     void loadProjectClientScript();
@@ -24,7 +24,6 @@ public:
 
     bool isFinished() const;
 private:
-    const Project& project;
     std::unique_ptr<scripting::IClientProjectScript> clientScript;
     std::unique_ptr<Process> scriptCoroutine;
 };
diff --git a/src/devtools/Project.hpp b/src/devtools/Project.hpp
index daeac7ca0..571a8b2c5 100644
--- a/src/devtools/Project.hpp
+++ b/src/devtools/Project.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "interfaces/Serializable.hpp"
+#include "io/path.hpp"
 
 #include <set>
 #include <string>
@@ -12,6 +13,7 @@ struct Permissions {
     static inline std::string NETWORK = "network";
     static inline std::string RECORD_AUDIO = "record-audio";
     static inline std::string WRITE_TO_USER = "write-to-user";
+    static inline std::string SUB_INSTANCES = "sub-instances";
 
     std::set<std::string> permissions;
 
@@ -21,6 +23,7 @@ struct Permissions {
 struct Project : Serializable {
     std::string name;
     std::string title;
+    io::path path;
     std::vector<std::string> basePacks;
     Permissions permissions;
 
diff --git a/src/engine/CoreParameters.hpp b/src/engine/CoreParameters.hpp
index b9f585f47..b5d8074ce 100644
--- a/src/engine/CoreParameters.hpp
+++ b/src/engine/CoreParameters.hpp
@@ -14,5 +14,6 @@ struct CoreParameters {
     std::filesystem::path projectFolder;
     std::string debugServerString;
     int tps = 20;
+    int subProcessDepth = 0;
     std::unordered_map<std::string, std::string> projectArgs;
 };
diff --git a/src/engine/Engine.cpp b/src/engine/Engine.cpp
index 10f8cee6d..f0e20f922 100644
--- a/src/engine/Engine.cpp
+++ b/src/engine/Engine.cpp
@@ -192,7 +192,7 @@ void Engine::initialize(CoreParameters coreParameters) {
         audio::set_input_device(name == "auto" ? "" : name);
     }));
 
-    appScripts = std::make_unique<AppScriptsControl>(params, *project);
+    appScripts = std::make_unique<AppScriptsControl>(params);
 
     if (params.stdinCommands) {
         cmd::start_stdin_cmd_reader(*this);
@@ -380,6 +380,7 @@ void Engine::loadAssets() {
 void Engine::loadProject() {
     io::path projectFile = "project:project.toml";
     project = std::make_unique<Project>();
+    project->path = "project:";
     project->deserialize(io::read_object(projectFile));
     logger.info() << "loaded project " << util::quote(project->name);
 }
@@ -412,6 +413,7 @@ void Engine::onWorldClosed() {
 }
 
 void Engine::quit() {
+    logger.info() << "quitSignal set to true";
     quitSignal = true;
     if (!isHeadless()) {
         window->setShouldClose(true);
diff --git a/src/engine/Mainloop.cpp b/src/engine/Mainloop.cpp
index 3a196f522..aa505a9ba 100644
--- a/src/engine/Mainloop.cpp
+++ b/src/engine/Mainloop.cpp
@@ -43,7 +43,7 @@ void Mainloop::run() {
     auto& appScripts = engine.getAppScripts();
     
     logger.info() << "main loop started";
-    while (!window.isShouldClose()) {
+    while (!window.isShouldClose() && !engine.isQuitSignal()) {
         time.update(window.time());
         engine.applicationTick();
         engine.updateFrontend();
diff --git a/src/frontend/ContentGfxCache.cpp b/src/frontend/ContentGfxCache.cpp
index b8ce69a5f..9cdcdf70e 100644
--- a/src/frontend/ContentGfxCache.cpp
+++ b/src/frontend/ContentGfxCache.cpp
@@ -30,6 +30,7 @@ void ContentGfxCache::refreshVariant(
     uint8_t variantIndex,
     const Atlas& atlas
 ) {
+    std::unordered_map<std::string, std::string> optionalTextures;
     bool denseRender = settings.denseRender.get();
     for (uint side = 0; side < 6; side++) {
         std::string tex = variant.textureFaces[side];
@@ -43,6 +44,7 @@ void ContentGfxCache::refreshVariant(
             texOpaque = tex;
         } else if (variant.culling == CullingMode::OPTIONAL && !denseRender) {
             tex = texOpaque;
+            optionalTextures[variant.textureFaces[side]] = texOpaque;
         }
         size_t index = getRegionIndex(def.rt.id, variantIndex, side, false);
         sideregions[index] = atlas.get(tex);
@@ -56,7 +58,12 @@ void ContentGfxCache::refreshVariant(
             if (pos == std::string::npos) {
                 continue;
             }
-            if (auto region = atlas.getIf(mesh.texture.substr(pos+1))) {
+            std::string texture = mesh.texture.substr(pos+1);
+            const auto& found = optionalTextures.find(texture);
+            if (found != optionalTextures.end()) {
+                texture = found->second;
+            }
+            if (auto region = atlas.getIf(texture)) {
                 for (auto& vertex : mesh.vertices) {
                     vertex.uv = region->apply(vertex.uv);
                 }
diff --git a/src/graphics/render/BlocksRenderer.cpp b/src/graphics/render/BlocksRenderer.cpp
index 6ccc5dcf6..f75bd675c 100644
--- a/src/graphics/render/BlocksRenderer.cpp
+++ b/src/graphics/render/BlocksRenderer.cpp
@@ -514,6 +514,7 @@ void BlocksRenderer::render(
         int x = i % CHUNK_W;
         int y = i / (CHUNK_D * CHUNK_W);
         int z = (i / CHUNK_D) % CHUNK_W;
+
         switch (def.getModel(state.userbits).type) {
             case BlockModelType::BLOCK:
                 blockCube({x, y, z}, texfaces, def, vox.state, !def.shadeless,
@@ -532,7 +533,6 @@ void BlocksRenderer::render(
                 break;
             }
             case BlockModelType::CUSTOM: {
-                if (!denseRender)
                 blockCustomModel(
                     {x, y, z},
                     def,
diff --git a/src/io/path.hpp b/src/io/path.hpp
index 538431b7c..3ab95300e 100644
--- a/src/io/path.hpp
+++ b/src/io/path.hpp
@@ -33,6 +33,8 @@ namespace io {
             }
         }
 
+        path(std::string_view str) : path(std::string(str)) {}
+
         path(const char* str) : path(std::string(str)) {}
 
         bool operator==(const std::string& other) const {
diff --git a/src/logic/scripting/lua/libs/libapp.cpp b/src/logic/scripting/lua/libs/libapp.cpp
index 6442fcbad..9157b33a6 100644
--- a/src/logic/scripting/lua/libs/libapp.cpp
+++ b/src/logic/scripting/lua/libs/libapp.cpp
@@ -20,8 +20,14 @@
 #include "window/Window.hpp"
 #include "world/Level.hpp"
 
+#include <array>
+
 using namespace scripting;
 
+namespace {
+    static std::array<std::unique_ptr<Process>, MAX_SUBPROCESSES> processes;
+}
+
 /// @brief Check if content is loaded
 static int l_is_content_loaded(lua::State* L) {
     return lua::pushboolean(L, content != nullptr);
@@ -337,6 +343,10 @@ static int l_start_debug_instance(lua::State* L) {
     if (!engine->getProject().permissions.has(Permissions::DEBUGGING)) {
         throw std::runtime_error("project has no debugging permission");
     }
+    const auto& params = engine->getCoreParameters();
+    if (params.subProcessDepth >= MAX_SUBPROCESS_DEPTH) {
+        throw std::runtime_error("max subprocess depth exceeded");
+    }
 
     int port = lua::tointeger(L, 1);
     if (port == 0) {
@@ -357,6 +367,8 @@ static int l_start_debug_instance(lua::State* L) {
         "--res", paths.getResourcesFolder().u8string(),
         "--dir", paths.getUserFilesFolder().u8string(),
         "--dbg-server",  "tcp:" + std::to_string(port),
+        "--sub-depth", std::to_string(engine->getCoreParameters()
+            .subProcessDepth + 1),
     };
     if (!projectPath.empty()) {
         args.emplace_back("--project");
@@ -365,11 +377,77 @@ static int l_start_debug_instance(lua::State* L) {
 
     platform::new_engine_instance(
         std::move(args),
-        outputPath.empty() ? "" : io::resolve(std::string(outputPath))
+        outputPath.empty() ? "" : io::resolve(std::string(outputPath)),
+        false
     );
     return lua::pushinteger(L, port);
 }
 
+static int l_start_background_instance(lua::State* L) {
+    if (!engine->getProject().permissions.has(Permissions::SUB_INSTANCES)) {
+        throw std::runtime_error("project has no sub-instances permission");
+    }
+    const auto& params = engine->getCoreParameters();
+    if (params.subProcessDepth >= MAX_SUBPROCESS_DEPTH) {
+        throw std::runtime_error("max subprocess depth exceeded");
+    }
+
+    auto scriptPath = lua::require_lstring(L, 1);
+    io::path outputPath = lua::isstring(L, 2) ? lua::require_lstring(L, 2) : "";
+    const auto& paths = engine->getPaths();
+
+    std::vector<std::string> args {
+        "--headless",
+        "--res", paths.getResourcesFolder().u8string(),
+        "--dir", paths.getUserFilesFolder().u8string(),
+        "--script", io::resolve(scriptPath).u8string(),
+        "--sub-depth", std::to_string(engine->getCoreParameters()
+            .subProcessDepth + 1),
+    };
+    args.emplace_back("--project");
+    args.emplace_back(io::resolve(engine->getProject().path).u8string());
+
+    int handle = -1;
+    for (int i = 0; i < ::processes.size(); i++) {
+        if (!::processes[i] || !::processes[i]->isActive()) {
+            handle = i;
+            break;
+        }
+    }
+    if (handle == -1) {
+        throw std::runtime_error("sub-processes limit exceeded");
+    }
+    ::processes[handle] = platform::new_engine_instance(
+        std::move(args),
+        outputPath.empty() ? "" : io::resolve(outputPath),
+        true 
+    );
+    return lua::pushinteger(L, handle);
+}
+
+static int l_is_instance_alive(lua::State* L) {
+    int handle = lua::tointeger(L, 1);
+    if (handle < 0 || handle >= ::processes.size()) {
+        throw std::runtime_error("invalid process handle");
+    }
+    auto& process = ::processes[handle];
+    return lua::pushboolean(L, process && process->isActive());
+}
+
+static int l_terminate_instance(lua::State* L) {
+    int handle = lua::tointeger(L, 1);
+    if (handle < 0 || handle >= ::processes.size()) {
+        throw std::runtime_error("invalid process handle");
+    }
+    auto& process = ::processes[handle];
+    if (process == nullptr) {
+        return lua::pushboolean(L, false);
+    }
+    bool active = process->isActive();
+    process.reset();
+    return lua::pushboolean(L, active);
+}
+
 const luaL_Reg applib[] = {
     /// content
     {"is_content_loaded", lua::wrap<l_is_content_loaded>},
@@ -402,5 +480,8 @@ const luaL_Reg applib[] = {
     {"get_version", lua::wrap<l_get_version>},
     {"create_memory_device", lua::wrap<l_create_memory_device>},
     {"start_debug_instance", lua::wrap<l_start_debug_instance>},
+    {"start_background_instance", lua::wrap<l_start_background_instance>},
+    {"is_instance_alive", lua::wrap<l_is_instance_alive>},
+    {"terminate_instance", lua::wrap<l_terminate_instance>},
     {nullptr, nullptr}
 };
diff --git a/src/logic/scripting/lua/libs/libentity.cpp b/src/logic/scripting/lua/libs/libentity.cpp
index 110aee123..4434136ba 100644
--- a/src/logic/scripting/lua/libs/libentity.cpp
+++ b/src/logic/scripting/lua/libs/libentity.cpp
@@ -311,6 +311,10 @@ static int l_world_raycast(lua::State* L) {
         entityRaycast.entityFilterExcludeMode = lua::toboolean(L, -1);
         lua::pop(L);
     }
+    if (lua::getfield(L, "nonselect_entities", 1)) {
+        entityRaycast.includeNonSelectable = lua::toboolean(L, -1);
+        lua::pop(L);
+    }
     if (lua::getfield(L, "filter_blocks", 1)) {
         load_blocks_filter(L, -1, filteredBlocks);
         blocksRaycast.filter = &filteredBlocks;
diff --git a/src/main.cpp b/src/main.cpp
index 77175bd8a..402b829b3 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -10,6 +10,7 @@
 static debug::Logger logger("main");
 
 static void sigterm_handler(int signum) {
+    logger.info() << (signum == SIGTERM ? "SIGTERM" : "SIGINT") << " received";
     Engine::getInstance().quit();
 }
 
@@ -25,12 +26,16 @@ int main(int argc, char** argv) {
         if (!parse_cmdline(argc, argv, coreParameters)) {
             return EXIT_SUCCESS;
         }
+        logger.debug() << "sub-process depth: "
+                       << coreParameters.subProcessDepth;
     } catch (const std::runtime_error& err) {
         std::cerr << err.what() << std::endl;
         return EXIT_FAILURE;
     }
     std::signal(SIGTERM, sigterm_handler);
-    
+#ifdef NDEBUG
+    std::signal(SIGINT, sigterm_handler);
+#endif
     debug::Logger::init(coreParameters.userFolder.string() + "/latest.log");
     platform::configure_encoding();
 
diff --git a/src/objects/Entities.cpp b/src/objects/Entities.cpp
index fafd99fe5..0902ae85a 100644
--- a/src/objects/Entities.cpp
+++ b/src/objects/Entities.cpp
@@ -176,7 +176,8 @@ std::optional<Entities::RaycastResult> Entities::rayCast(
 
     for (auto [entity, eid, transform, body] : view.each()) {
         if (eid.uid == settings.ignoredUid || !body.enabled ||
-            (settings.solidEntitiesOnly && !eid.def.solid)) {
+            (settings.solidEntitiesOnly && !eid.def.solid) ||
+            (!eid.def.selectable && !settings.includeNonSelectable)) {
             continue;
         }
         if (settings.entitiesFilter) {
diff --git a/src/objects/Entities.hpp b/src/objects/Entities.hpp
index 0d003ffb1..382790b95 100644
--- a/src/objects/Entities.hpp
+++ b/src/objects/Entities.hpp
@@ -85,6 +85,7 @@ public:
         bool solidEntitiesOnly = false;
         bool entityFilterExcludeMode = false;
         const std::set<entitydefid_t>* entitiesFilter = nullptr;
+        bool includeNonSelectable = false;
     };
 
     struct RaycastResult {
diff --git a/src/objects/EntityDef.hpp b/src/objects/EntityDef.hpp
index 6ecb1c917..59aed2d7e 100644
--- a/src/objects/EntityDef.hpp
+++ b/src/objects/EntityDef.hpp
@@ -42,6 +42,9 @@ struct EntityDef {
     /// @brief Solid entity material material
     std::string material;
 
+    /// @brief Can the entity be interacted with cursor (on_attack, on_use)
+    bool selectable = true;
+
     /// @brief Does entity prevent blocks setup
     bool blocking = true;
 
diff --git a/src/util/command_line.cpp b/src/util/command_line.cpp
index 7f34bcea4..f05231821 100644
--- a/src/util/command_line.cpp
+++ b/src/util/command_line.cpp
@@ -13,22 +13,22 @@
 namespace fs = std::filesystem;
 
 class ArgC {
-    public:
-        std::string keyword;
-        std::function<bool()> execute;
-        std::string args;
-        std::string help;
-        ArgC(
-            const std::string& keyword,
-            std::function<bool()> execute,
-            const std::string& args,
-            const std::string& help
-        ) {
-            this->keyword = keyword;
-            this->execute = execute;
-            this->args = args;
-            this->help = help;
-        }
+public:
+    std::string keyword;
+    std::function<bool(CoreParameters&, util::ArgsReader&)> execute;
+    std::string args;
+    std::string help;
+    ArgC(
+        const std::string& keyword,
+        std::function<bool(CoreParameters&, util::ArgsReader&)> execute,
+        const std::string& args,
+        const std::string& help
+    ) {
+        this->keyword = keyword;
+        this->execute = execute;
+        this->args = args;
+        this->help = help;
+    }
 };
 
 
@@ -36,54 +36,62 @@ static bool perform_keyword(
     util::ArgsReader& reader, const std::string& keyword, CoreParameters& params
 ) {
     static const std::vector<ArgC> argumentsCommandline = {
-        ArgC("--res", [&params, &reader]() -> bool {
+        ArgC("--res", [](auto& params, auto& reader) -> bool {
             params.resFolder = reader.next();
             return true;
         }, "<path>", "set resources directory."),
-        ArgC("--dir", [&params, &reader]() -> bool {
+        ArgC("--dir", [](auto& params, auto& reader) -> bool  {
             params.userFolder = reader.next();
             return true;
         }, "<path>", "set userfiles directory."),
-        ArgC("--project", [&params, &reader]() -> bool {
+        ArgC("--project", [](auto& params, auto& reader) -> bool  {
             params.projectFolder = reader.next();
             return true;
         }, "<path>", "set project directory."),
-        ArgC("--test", [&params, &reader]() -> bool {
+        ArgC("--test", [](auto& params, auto& reader) -> bool {
             params.testMode = true;
             params.scriptFile = reader.next();
             return true;
         }, "<path>", "test script file."),
-        ArgC("--script", [&params, &reader]() -> bool {
+        ArgC("--script", [](auto& params, auto& reader) -> bool {
             params.testMode = false;
             params.scriptFile = reader.next();
             return true;
         }, "<path>", "main script file."),
-        ArgC("--headless", [&params]() -> bool {
+        ArgC("--headless", [](auto& params, auto& reader) -> bool {
             params.headless = true;
             return true;
         }, "", "run in headless mode."),
-        ArgC("--stdin-cmd", [&params]() -> bool {
+        ArgC("--stdin-cmd", [](auto& params, auto& reader) -> bool {
             params.stdinCommands = true;
             return true;
         }, "", "run commands from stdin."),
-        ArgC("--tps", [&params, &reader]() -> bool {
+        ArgC("--tps", [](auto& params, auto& reader) -> bool {
             params.tps = reader.nextInt();
             return true;
         }, "<tps>", "headless mode tick-rate (default - 20)."),
-        ArgC("--version", []() -> bool {
+        ArgC("--version", [](auto&, auto&) -> bool {
             std::cout << ENGINE_VERSION_STRING << std::endl;
             return false;
         }, "", "display the engine version."),
-        ArgC("--dbg-server", [&params, &reader]() -> bool {
+        ArgC("--dbg-server", [](auto& params, auto& reader) -> bool {
             params.debugServerString = reader.next();
             return true;
         }, "<serv>", "open debugging server where <serv> is {transport}:{port}"),
-        ArgC("--help", []() -> bool {
+        ArgC("--sub-depth", [](auto& params, auto& reader) -> bool {
+            params.subProcessDepth = reader.nextInt();
+            return true;
+        }, "<depth>", "sub-process depth"),
+        ArgC("--help", [](auto&, auto&) -> bool {
             std::cout << "VoxelCore v" << ENGINE_VERSION_STRING << "\n\n";
             std::cout << "Command-line arguments:\n";
-            for (auto& a : argumentsCommandline) {
-                std::cout << std::setw(24) << std::left << (a.keyword + " " + a.args);
-                std::cout << "- " << a.help << std::endl;
+            for (auto& arg : argumentsCommandline) {
+                if (arg.help.empty()) {
+                    continue;
+                }
+                std::cout << std::setw(24) << std::left
+                          << (arg.keyword + " " + arg.args);
+                std::cout << "- " << arg.help << std::endl;
             }
             std::cout << std::endl;
             return false;
@@ -91,7 +99,7 @@ static bool perform_keyword(
     };
     for (auto& a : argumentsCommandline) {
         if (a.keyword == keyword) {
-            return a.execute();
+            return a.execute(params, reader);
         }
     }
     throw std::runtime_error("unknown argument " + keyword);
diff --git a/src/util/platform.cpp b/src/util/platform.cpp
index f113641e5..7b08639e9 100644
--- a/src/util/platform.cpp
+++ b/src/util/platform.cpp
@@ -19,6 +19,13 @@
 #else
 #include <sys/poll.h>
 #include <unistd.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#endif
+#ifdef __linux__
+    #include <sys/prctl.h>
+    #include <sys/wait.h>
 #endif
 
 namespace platform::internal {
@@ -215,8 +222,102 @@ std::filesystem::path platform::get_executable_path() {
 #endif
 }
 
-void platform::new_engine_instance(
-    const std::vector<std::string>& args, std::filesystem::path outputFile
+class SystemProcess final : public Process {
+public:
+#ifdef __linux__
+    SystemProcess(pid_t pid) : pid(pid) {
+    }
+
+    ~SystemProcess() {
+        terminate();
+    }
+#elif defined(_WIN32)
+    SystemProcess(const PROCESS_INFORMATION& pi)
+        : processHandle(pi.hProcess), pid(pi.dwProcessId) {
+        if (pi.hThread != nullptr) {
+            CloseHandle(pi.hThread);
+        }
+    }
+
+    ~SystemProcess() {
+        terminate();
+    }
+#endif
+    SystemProcess(const SystemProcess&) = delete;
+    SystemProcess(SystemProcess&&) noexcept = default;
+    SystemProcess& operator=(const SystemProcess&) = delete;
+
+    SystemProcess& operator=(SystemProcess&& other) noexcept {
+        if (this != &other) {
+#ifdef __linux__
+            pid = other.pid;
+#elif defined(_WIN32)
+            if (processHandle != nullptr) {
+                CloseHandle(processHandle);
+            }
+            processHandle = other.processHandle;
+            pid = other.pid;
+            other.processHandle = nullptr;
+            other.pid = 0;
+#endif
+        }
+        return *this;
+    }
+
+    bool isActive() const override {
+#ifdef __linux__
+        if (kill(pid, 0) == 0) {
+            return true;
+        }
+        return errno != ESRCH;
+#elif defined(_WIN32)
+        if (processHandle == nullptr) {
+            return false;
+        }
+        DWORD exitCode;
+        if (GetExitCodeProcess(processHandle, &exitCode)) {
+            return exitCode == STILL_ACTIVE;
+        }
+        return false;
+#endif
+    }
+
+    void update() override {}
+
+    void waitForEnd() override {
+#ifdef __linux__
+        waitpid(pid, nullptr, 0);
+#elif defined(_WIN32)
+        if (processHandle != nullptr) {
+            WaitForSingleObject(processHandle, INFINITE);
+        }
+#endif
+    };
+
+    void terminate() final override {
+#ifdef __linux__
+        logger.info() << "terminating " << pid;
+        kill(pid, SIGTERM);
+#elif defined(_WIN32)
+        if (processHandle != nullptr) {
+            TerminateProcess(processHandle, 1);
+            WaitForSingleObject(processHandle, INFINITE);
+        }
+#endif
+    }
+private:
+#ifdef __linux__
+    pid_t pid;
+#elif defined(_WIN32)
+    HANDLE processHandle = nullptr;
+    DWORD pid = 0;
+#endif
+};
+
+std::unique_ptr<Process> platform::new_engine_instance(
+    const std::vector<std::string>& args,
+    std::filesystem::path outputFile,
+    bool subProcess
 ) {
     auto executable = get_executable_path();
 
@@ -285,6 +386,38 @@ void platform::new_engine_instance(
         &si,
         &pi
     );
+    if (subProcess) {
+        HANDLE job = CreateJobObjectW(nullptr, nullptr);
+
+        JOBOBJECT_EXTENDED_LIMIT_INFORMATION info{};
+        info.BasicLimitInformation.LimitFlags =
+            JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
+
+        try {
+            if (!SetInformationJobObject(
+                job,
+                JobObjectExtendedLimitInformation,
+                &info,
+                sizeof(info))) {
+                throw std::runtime_error(
+                    "SetInformationJobObject failed with code: " +
+                    std::to_string(GetLastError())
+                );
+            }
+            if (!AssignProcessToJobObject(job, pi.hProcess)) {
+                throw std::runtime_error(
+                    "SetInformationJobObject failed with code: " +
+                    std::to_string(GetLastError())
+                );
+            }
+            return std::make_unique<SystemProcess>(pi);
+        } catch (const std::exception& err) {
+            CloseHandle(job);
+            CloseHandle(pi.hProcess);
+            CloseHandle(pi.hThread);
+            return nullptr;
+        }
+    }
     if (success) {
         CloseHandle(pi.hProcess);
         CloseHandle(pi.hThread);
@@ -295,6 +428,46 @@ void platform::new_engine_instance(
         );
     }
 #else
+
+// TODO: implement
+#ifndef __APPLE__
+    if (subProcess) {
+        pid_t pid = fork();
+
+        int fd = open(
+            outputFile.string().c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0644
+        );
+
+        if (pid == 0) {
+            prctl(PR_SET_PDEATHSIG, SIGTERM);
+
+            if (getppid() == 1) {
+                _exit(1);
+            }
+
+            dup2(fd, STDOUT_FILENO);
+            dup2(fd, STDERR_FILENO);
+            close(fd);
+
+            std::vector<const char*> argv(args.size() + 2);
+            argv[0] = const_cast<char*>(executable.c_str());
+            for (int i = 0; i < args.size(); i++) {
+                argv[i + 1] = args[i].c_str();
+            }
+            argv[args.size() + 1] = nullptr;
+
+            prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); 
+            execvp(executable.c_str(), const_cast<char**>(argv.data()));
+
+            _exit(127);
+        } else {
+            close(fd);
+            usleep(1000); // waiting for execvp call
+            return std::make_unique<SystemProcess>(pid);
+        }
+    }
+#endif
+
     std::stringstream ss;
     ss << executable;
     for (int i = 0; i < args.size(); i++) {
@@ -315,6 +488,7 @@ void platform::new_engine_instance(
         );
     }
 #endif
+    return nullptr;
 }
 
 bool platform::stdin_has_data() {
diff --git a/src/util/platform.hpp b/src/util/platform.hpp
index 54c56a0c5..18dc052b6 100644
--- a/src/util/platform.hpp
+++ b/src/util/platform.hpp
@@ -2,8 +2,11 @@
 
 #include <string>
 #include <vector>
+#include <memory>
 #include <filesystem>
 
+#include "interfaces/Process.hpp"
+
 namespace platform {
     void configure_encoding();
     /// @brief Get Environment locale in ISO format ll_CC
@@ -18,8 +21,10 @@ namespace platform {
     /// @brief Get current process running executable path  
     std::filesystem::path get_executable_path();
     /// @brief Run a separate engine instance with specified arguments
-    void new_engine_instance(
-        const std::vector<std::string>& args, std::filesystem::path outputFile
+    std::unique_ptr<Process> new_engine_instance(
+        const std::vector<std::string>& args,
+        std::filesystem::path outputFile,
+        bool subProcess
     );
     /// @brief Open URL in web browser 
     bool open_url(const std::string& url);
diff --git a/src/voxels/Block.hpp b/src/voxels/Block.hpp
index 5ba3bb267..ded51244e 100644
--- a/src/voxels/Block.hpp
+++ b/src/voxels/Block.hpp
@@ -37,8 +37,6 @@ inline constexpr size_t MAX_USER_BLOCK_FIELDS_SIZE = 240;
 
 inline constexpr int BLOCK_MAX_VARIANTS = 16;
 
-inline std::string DEFAULT_MATERIAL = "base:stone";
-
 struct BlockFuncsSet {
     bool init : 1;
     bool update : 1;
@@ -206,7 +204,7 @@ public:
     dv::value properties = nullptr;
 
     /// @brief id of used BlockMaterial, may specify non-existing material
-    std::string material = DEFAULT_MATERIAL;
+    std::string material;
 
     /// @brief Light emission R, G, B, S (sky lights: sun, moon, radioactive
     /// clouds)