diff --git a/src/Engine.cpp b/src/Engine.cpp
index c10e3e7..3469a33 100644
--- a/src/Engine.cpp
+++ b/src/Engine.cpp
@@ -4,7 +4,7 @@
 namespace ougge {
 
 Engine::Engine()
-    : gameObjectPool(GAMEOBJECTPOOL_SIZE) 
+    : gameObjectPool(GAMEOBJECTPOOL_SIZE), textures(&resourceManager)
 {
 }
 
@@ -17,7 +17,7 @@ void Engine::init(){
 }
 
 void Engine::openMainWindow(const std::string& window_title){
-    mainWindow.open(window_title);
+    mainWindow.open(window_title, resourceManager);
 }
 
 void Engine::startLoop(){
diff --git a/src/Engine.hpp b/src/Engine.hpp
index 413cbcb..d55609e 100644
--- a/src/Engine.hpp
+++ b/src/Engine.hpp
@@ -1,50 +1,51 @@
-#pragma once
-
-#include "common/function_shared_ptr.hpp"
-#include "mono/mono.hpp"
-#include "game/GameObjectPool.hpp"
-#include "gui/MainWindow.hpp"
-#include "resources/textures.hpp"
-
-namespace ougge {
-
-#define GAMEOBJECTPOOL_SIZE 64*1024
-
-using UpdateFunc_t = function_shared_ptr<void(f64)>;
-
-class Engine {
-    bool loop_running = false;
-
-    game::GameObjectPool gameObjectPool;
-    u64 obj_id = 0;
-    MonoClass* gameObjectClass;
-    Mono::Method<void(u64, u32)> gameObjectCtor;
-    Mono::Method<void(f64)> gameObjectInvokeUpdate;
-    Mono::Method<Mono::Bool(Mono::String)> gameObjectTryCreateComponent;
-    
-public:
-    gui::MainWindow mainWindow;
-    UpdateFunc_t updateCallback;
-
-    Mono::RuntimeJIT mono;
-    std::shared_ptr<Mono::Assembly> engineManagedAssembly;
-
-    resources::CacheStorage<resources::Texture> textures;
-
-    Engine();
-    void init();
-    void openMainWindow(const std::string& window_title);
-    // start game loop on the current thread
-    void startLoop();
-    void stopLoop();
-
-    game::GameObject& createGameObject();
-    bool tryCreateComponent(game::GameObject& obj, const std::string& componentClassName);
-    
-
-private:
-    void tryDrawFrame(f64 deltaTime);
-    void updateGameObjects(f64 deltaTime);
-};
-
-}
+#pragma once
+
+#include "common/function_shared_ptr.hpp"
+#include "mono/mono.hpp"
+#include "game/GameObjectPool.hpp"
+#include "gui/MainWindow.hpp"
+#include "resources/textures.hpp"
+
+namespace ougge {
+
+#define GAMEOBJECTPOOL_SIZE 64*1024
+
+using UpdateFunc_t = function_shared_ptr<void(f64)>;
+
+class Engine {
+    bool loop_running = false;
+
+    game::GameObjectPool gameObjectPool;
+    u64 obj_id = 0;
+    MonoClass* gameObjectClass;
+    Mono::Method<void(u64, u32)> gameObjectCtor;
+    Mono::Method<void(f64)> gameObjectInvokeUpdate;
+    Mono::Method<Mono::Bool(Mono::String)> gameObjectTryCreateComponent;
+    
+public:
+    gui::MainWindow mainWindow;
+    UpdateFunc_t updateCallback;
+
+    Mono::RuntimeJIT mono;
+    std::shared_ptr<Mono::Assembly> engineManagedAssembly;
+
+    resources::ResourceManager resourceManager;
+    resources::CacheStorage<resources::Texture> textures;
+
+    Engine();
+    void init();
+    void openMainWindow(const std::string& window_title);
+    // start game loop on the current thread
+    void startLoop();
+    void stopLoop();
+
+    game::GameObject& createGameObject();
+    bool tryCreateComponent(game::GameObject& obj, const std::string& componentClassName);
+    
+
+private:
+    void tryDrawFrame(f64 deltaTime);
+    void updateGameObjects(f64 deltaTime);
+};
+
+}
diff --git a/src/GUI/MainWindow.cpp b/src/GUI/MainWindow.cpp
index a895cfb..d130517 100644
--- a/src/GUI/MainWindow.cpp
+++ b/src/GUI/MainWindow.cpp
@@ -4,8 +4,6 @@
 #include "MainWindow.hpp"
 #include "gui_exceptions.hpp"
 #include "../common/ougge_format.hpp"
-#include "../resources/fonts.hpp"
-#include "../resources/textures.hpp"
 #include "../common/math.hpp"
 
 namespace ougge::gui {
@@ -21,7 +19,7 @@ f32 MainWindow::getDPI(){
     return dpi;
 }
 
-void MainWindow::open(const std::string& window_title){
+void MainWindow::open(const std::string& window_title, resources::ResourceManager& resourceManager){
     SDL_TRY(SDL_Init(SDL_INIT_EVERYTHING));
     SDL_version v;
     SDL_GetVersion(&v);
@@ -72,8 +70,12 @@ void MainWindow::open(const std::string& window_title){
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
+    
+    resources::ResourceFactory* font_res = resourceManager.tryGetResource(default_font_path);
+    if(font_res == nullptr)
+        throw UsefulException("can't find default font resource");
     f32 dpi = getDPI();
-    io.FontDefault = resources::ImFont_LoadFromResource(default_font, default_font_size, dpi);
+    io.FontDefault = resources::ImFont_LoadFromResource(font_res, default_font_size, dpi);
 }
 
 void MainWindow::close(){
diff --git a/src/GUI/MainWindow.hpp b/src/GUI/MainWindow.hpp
index 70fad7a..c2c7b67 100644
--- a/src/GUI/MainWindow.hpp
+++ b/src/GUI/MainWindow.hpp
@@ -1,45 +1,47 @@
-#pragma once
-
-#include <SDL.h>
-#include <imgui.h>
-#include "../common/std.hpp"
-#include "../common/time.hpp"
-
-/// converts hex color to float vector
-#define RGBAHexToF(R8,G8,B8,A8) ImVec4(((u8)35)/255.0f, ((u8)35)/255.0f, ((u8)50)/255.0f, ((u8)255)/255.0f)
-/// converts float vector to hex color
-#define RGBAFToHex(VEC4) {(u8)(VEC4.x*255), (u8)(VEC4.y*255), (u8)(VEC4.z*255), (u8)(VEC4.w*255)}
-
-namespace ougge::gui {
-
-#define default_font "DroidSans"
-
-class MainWindow {
-public:
-    i32 fps_max = 60;
-    f32 default_font_size = 14.0f;
-    ImVec4 clear_color = RGBAHexToF(35,35,50,255);
-    SDL_Window* sdl_window = nullptr;
-    SDL_Renderer* sdl_renderer = nullptr;
-
-private:
-    bool show_debug_window = true;
-    bool show_demo_window = false;
-    bool show_metrics_window = false;
-
-public:
-    void open(const std::string& window_title);
-    void close();
-
-    /// process io events happened since previous frame
-    void pollEvents(bool* loopRunning);
-    void beginFrame();
-    void endFrame();
-
-    f32 getDPI();
-private:
-    void draw_debug_window();
-    void draw_bg_window();
-};
-
-}
+#pragma once
+
+#include <SDL.h>
+#include <imgui.h>
+#include "../common/std.hpp"
+#include "../common/time.hpp"
+#include "../resources/resources.hpp"
+#include "../resources/fonts.hpp"
+
+/// converts hex color to float vector
+#define RGBAHexToF(R8,G8,B8,A8) ImVec4(((u8)35)/255.0f, ((u8)35)/255.0f, ((u8)50)/255.0f, ((u8)255)/255.0f)
+/// converts float vector to hex color
+#define RGBAFToHex(VEC4) {(u8)(VEC4.x*255), (u8)(VEC4.y*255), (u8)(VEC4.z*255), (u8)(VEC4.w*255)}
+
+namespace ougge::gui {
+
+#define default_font_path "fonts/DroidSans.ttf"
+
+class MainWindow {
+public:
+    i32 fps_max = 60;
+    f32 default_font_size = 14.0f;
+    ImVec4 clear_color = RGBAHexToF(35,35,50,255);
+    SDL_Window* sdl_window = nullptr;
+    SDL_Renderer* sdl_renderer = nullptr;
+
+private:
+    bool show_debug_window = true;
+    bool show_demo_window = false;
+    bool show_metrics_window = false;
+
+public:
+    void open(const std::string& window_title, resources::ResourceManager& resourceManager);
+    void close();
+
+    /// process io events happened since previous frame
+    void pollEvents(bool* loopRunning);
+    void beginFrame();
+    void endFrame();
+
+    f32 getDPI();
+private:
+    void draw_debug_window();
+    void draw_bg_window();
+};
+
+}
diff --git a/src/Resources/MemorySteam.cpp b/src/Resources/MemorySteam.cpp
new file mode 100644
index 0000000..fea56e5
--- /dev/null
+++ b/src/Resources/MemorySteam.cpp
@@ -0,0 +1,40 @@
+#include "MemoryStream.hpp"
+
+class MemoryStreamBuf : public std::streambuf {
+public:
+    MemoryStreamBuf(void* p, const std::size_t n);
+
+    virtual std::istream::pos_type seekoff(
+        std::istream::off_type off,
+        std::ios_base::seekdir dir,
+        std::ios_base::openmode which);
+};
+
+MemoryStreamBuf::MemoryStreamBuf(void* _p, const std::size_t n){
+    char* p=(char*)_p;
+    setg(p, p, p + n);
+    setp(p, p + n);
+}
+
+std::istream::pos_type MemoryStreamBuf::seekoff(
+    std::istream::off_type off,
+    std::ios_base::seekdir dir,
+    std::ios_base::openmode which)
+{
+    if (dir == std::ios_base::cur)
+        gbump(off);
+    else if (dir == std::ios_base::end)
+        setg(eback(), egptr() + off, egptr());
+    else if (dir == std::ios_base::beg)
+        setg(eback(), eback() + off, egptr());
+    return gptr() - eback();
+}
+
+
+MemoryStreamRead::MemoryStreamRead(const void* p, const std::size_t n)
+    : std::istream(new MemoryStreamBuf((void*)p, n))
+{}
+
+MemoryStreamRead::~MemoryStreamRead(){
+    delete rdbuf();
+}
diff --git a/src/Resources/MemoryStream.hpp b/src/Resources/MemoryStream.hpp
new file mode 100644
index 0000000..0f1ced9
--- /dev/null
+++ b/src/Resources/MemoryStream.hpp
@@ -0,0 +1,8 @@
+#include <iostream>
+
+class MemoryStreamRead : public std::istream {
+public:
+    MemoryStreamRead(const void* p, const std::size_t n);
+
+    virtual ~MemoryStreamRead();
+};
\ No newline at end of file
diff --git a/src/Resources/fonts.cpp b/src/Resources/fonts.cpp
index 3ce4b5b..96cde0f 100644
--- a/src/Resources/fonts.cpp
+++ b/src/Resources/fonts.cpp
@@ -1,7 +1,4 @@
-#include <imgui.h>
-#include "resources.hpp"
-#include <cstdio>
-#include <cstring>
+#include "fonts.hpp"
 
 namespace ougge::resources {
 
@@ -16,17 +13,16 @@ ImFont* ImFont_LoadFromFile(const std::string& file_path, f32 font_size, f32 dpi
     return io.Fonts->AddFontFromFileTTF(file_path.c_str(), font_size, nullptr, glyph_ranges);
 }
 
-ImFont* ImFont_LoadFromResource(const std::string& font_name, f32 font_size, f32 dpi){
+ImFont* ImFont_LoadFromResource(ResourceFactory* res, f32 font_size, f32 dpi){
     ImGuiIO& io = ImGui::GetIO();
     font_size *= dpi;
     ImFontConfig font_cfg = ImFontConfig();
-    std::sprintf(font_cfg.Name, "%s %ipx", font_name.c_str(), (i32)font_size);
+    std::sprintf(font_cfg.Name, "%s %ipx", res->path.c_str(), (i32)font_size);
     
-    auto& res = getResource("fonts/" + font_name + ".ttf");
-    char* font_data = new char[res.size]; 
-    res.openStream()->read(font_data, res.size);
+    char* font_data = new char[res->size]; 
+    res->openStream()->read(font_data, res->size);
 
-    return io.Fonts->AddFontFromMemoryTTF((void*)(font_data), res.size,
+    return io.Fonts->AddFontFromMemoryTTF((void*)(font_data), res->size,
         font_size, &font_cfg, glyph_ranges);
 }
 
diff --git a/src/Resources/fonts.hpp b/src/Resources/fonts.hpp
index 22bf712..6ab1b08 100644
--- a/src/Resources/fonts.hpp
+++ b/src/Resources/fonts.hpp
@@ -1,12 +1,13 @@
 #pragma once
 
-#include "imgui.h"
+#include <imgui.h>
 #include "../common/std.hpp"
+#include "resources.hpp"
 
 namespace ougge::resources {
 
 ImFont* ImFont_LoadFromFile(const std::string& file_path, f32 font_size, f32 dpi);
 
-ImFont* ImFont_LoadFromResource(const std::string& font_name, f32 font_size, f32 dpi);
+ImFont* ImFont_LoadFromResource(ResourceFactory* res, f32 font_size, f32 dpi);
 
 }
diff --git a/src/common/ougge_format.cpp b/src/common/ougge_format.cpp
index a8f5a6d..f3f7642 100644
--- a/src/common/ougge_format.cpp
+++ b/src/common/ougge_format.cpp
@@ -1,65 +1,84 @@
-#include <sstream>
-#include <stdarg.h>
-#include "ougge_format.hpp"
-#include "UsefulException.hpp"
-
-std::string _ougge_format(const std::string& format_str, const size_t args_count, ...){
-    va_list vl;
-    va_start(vl, args_count);
-    std::stringstream ss;
-    
-    for(size_t i = 0; i < format_str.length(); i++){
-        char c = format_str[i];
-
-        // format specifier
-        if(c == '%'){
-            c = format_str[++i];
-            bool l = false;
-            while(c == 'l'){
-                l = true;
-                c = format_str[++i];
-            }
-            
-            switch(c){
-                case 'u':
-                    if(l) ss<<(u64)va_arg(vl, u64);
-                    else ss<<(u32)va_arg(vl, u32);
-                    break;
-                case 'i':
-                case 'd':
-                    if(l) ss<<(i64)va_arg(vl, i64);
-                    else ss<<(i32)va_arg(vl, i32);
-                    break;
-                case 'f':
-                    // f32 is promoted to f64 when passed through '...'
-                    ss<<(f64)va_arg(vl, f64);
-                    break;
-                case 'p':
-                    ss<<(void*)va_arg(vl, void*);
-                    break;
-                case 'x':
-                    if(l) ss<<std::hex<<(u64)va_arg(vl, u64);
-                    else ss<<std::hex<<(u32)va_arg(vl, u32);
-                    break;
-                case 's': {
-                    const char* cptr = va_arg(vl,char*);
-                    if(cptr != nullptr)
-                        ss<<cptr;
-                    else ss<<"<nullptr>";
-                    break;
-                }
-                case 'c':
-                    ss<<(char)va_arg(vl,int);
-                    break;
-                default:
-                    throw UsefulException("invalid format cpecifier");
-            }
-        }
-
-        // regular character
-        else ss<<c;
-    }
-
-    va_end(vl);
-    return ss.str();
-}
+#include <sstream>
+#include <stdarg.h>
+#include "ougge_format.hpp"
+#include "UsefulException.hpp"
+
+std::string _ougge_format(const std::string& format_str, const size_t args_count, ...){
+    va_list vl;
+    va_start(vl, args_count);
+    std::stringstream ss;
+    
+    for(size_t i = 0; i < format_str.length(); i++){
+        char c = format_str[i];
+
+        // format specifier
+        if(c == '%'){
+            c = format_str[++i];
+            bool l = false;
+            while(c == 'l'){
+                l = true;
+                c = format_str[++i];
+            }
+            
+            switch(c){
+                case 'u':
+                    if(l) ss<<(u64)va_arg(vl, u64);
+                    else ss<<(u32)va_arg(vl, u32);
+                    break;
+                case 'i':
+                case 'd':
+                    if(l) ss<<(i64)va_arg(vl, i64);
+                    else ss<<(i32)va_arg(vl, i32);
+                    break;
+                case 'f':
+                    // f32 is promoted to f64 when passed through '...'
+                    ss<<(f64)va_arg(vl, f64);
+                    break;
+                case 'p':
+                    ss<<(void*)va_arg(vl, void*);
+                    break;
+                case 'x':
+                    if(l) ss<<std::hex<<(u64)va_arg(vl, u64);
+                    else ss<<std::hex<<(u32)va_arg(vl, u32);
+                    break;
+                case 's': {
+                    const char* cptr = va_arg(vl,char*);
+                    if(cptr != nullptr)
+                        ss<<cptr;
+                    else ss<<"<nullptr>";
+                    break;
+                }
+                case 'c':
+                    ss<<(char)va_arg(vl,int);
+                    break;
+                default:
+                    throw UsefulException("invalid format cpecifier");
+            }
+        }
+
+        // regular character
+        else ss<<c;
+    }
+
+    va_end(vl);
+    return ss.str();
+}
+
+
+std::string formatSizeHumanReadable(std::size_t b){
+    std::stringstream ss;
+    ss.precision(3);
+    std::size_t k = b / 1024;
+    std::size_t m = k / 1024;
+    std::size_t g = m / 1024;
+    
+    if(g)
+        ss<<m / 1024.0f<<'G';
+    else if(m)
+        ss<<k / 1024.0f<<'M';
+    else if(k)
+        ss<<b / 1024.0f<<'K';
+    else ss<<b;
+
+    return ss.str();
+}
diff --git a/src/common/ougge_format.hpp b/src/common/ougge_format.hpp
index 9eb8203..64ce2ab 100644
--- a/src/common/ougge_format.hpp
+++ b/src/common/ougge_format.hpp
@@ -1,6 +1,8 @@
-#pragma once
-
-#include "std.hpp"
-
-std::string _ougge_format(const std::string& format_str, const size_t args_count, ...);
-#define ougge_format(FORMAT_STR, ARGS...) _ougge_format(FORMAT_STR, count_args(ARGS) ,##ARGS)
+#pragma once
+
+#include "std.hpp"
+
+std::string _ougge_format(const std::string& format_str, const size_t args_count, ...);
+#define ougge_format(FORMAT_STR, ARGS...) _ougge_format(FORMAT_STR, count_args(ARGS) ,##ARGS)
+
+std::string formatSizeHumanReadable(std::size_t byte_n);
diff --git a/src/gui/MainWindow.cpp b/src/gui/MainWindow.cpp
index a895cfb..d130517 100644
--- a/src/gui/MainWindow.cpp
+++ b/src/gui/MainWindow.cpp
@@ -4,8 +4,6 @@
 #include "MainWindow.hpp"
 #include "gui_exceptions.hpp"
 #include "../common/ougge_format.hpp"
-#include "../resources/fonts.hpp"
-#include "../resources/textures.hpp"
 #include "../common/math.hpp"
 
 namespace ougge::gui {
@@ -21,7 +19,7 @@ f32 MainWindow::getDPI(){
     return dpi;
 }
 
-void MainWindow::open(const std::string& window_title){
+void MainWindow::open(const std::string& window_title, resources::ResourceManager& resourceManager){
     SDL_TRY(SDL_Init(SDL_INIT_EVERYTHING));
     SDL_version v;
     SDL_GetVersion(&v);
@@ -72,8 +70,12 @@ void MainWindow::open(const std::string& window_title){
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
+    
+    resources::ResourceFactory* font_res = resourceManager.tryGetResource(default_font_path);
+    if(font_res == nullptr)
+        throw UsefulException("can't find default font resource");
     f32 dpi = getDPI();
-    io.FontDefault = resources::ImFont_LoadFromResource(default_font, default_font_size, dpi);
+    io.FontDefault = resources::ImFont_LoadFromResource(font_res, default_font_size, dpi);
 }
 
 void MainWindow::close(){
diff --git a/src/gui/MainWindow.hpp b/src/gui/MainWindow.hpp
index 70fad7a..c2c7b67 100644
--- a/src/gui/MainWindow.hpp
+++ b/src/gui/MainWindow.hpp
@@ -1,45 +1,47 @@
-#pragma once
-
-#include <SDL.h>
-#include <imgui.h>
-#include "../common/std.hpp"
-#include "../common/time.hpp"
-
-/// converts hex color to float vector
-#define RGBAHexToF(R8,G8,B8,A8) ImVec4(((u8)35)/255.0f, ((u8)35)/255.0f, ((u8)50)/255.0f, ((u8)255)/255.0f)
-/// converts float vector to hex color
-#define RGBAFToHex(VEC4) {(u8)(VEC4.x*255), (u8)(VEC4.y*255), (u8)(VEC4.z*255), (u8)(VEC4.w*255)}
-
-namespace ougge::gui {
-
-#define default_font "DroidSans"
-
-class MainWindow {
-public:
-    i32 fps_max = 60;
-    f32 default_font_size = 14.0f;
-    ImVec4 clear_color = RGBAHexToF(35,35,50,255);
-    SDL_Window* sdl_window = nullptr;
-    SDL_Renderer* sdl_renderer = nullptr;
-
-private:
-    bool show_debug_window = true;
-    bool show_demo_window = false;
-    bool show_metrics_window = false;
-
-public:
-    void open(const std::string& window_title);
-    void close();
-
-    /// process io events happened since previous frame
-    void pollEvents(bool* loopRunning);
-    void beginFrame();
-    void endFrame();
-
-    f32 getDPI();
-private:
-    void draw_debug_window();
-    void draw_bg_window();
-};
-
-}
+#pragma once
+
+#include <SDL.h>
+#include <imgui.h>
+#include "../common/std.hpp"
+#include "../common/time.hpp"
+#include "../resources/resources.hpp"
+#include "../resources/fonts.hpp"
+
+/// converts hex color to float vector
+#define RGBAHexToF(R8,G8,B8,A8) ImVec4(((u8)35)/255.0f, ((u8)35)/255.0f, ((u8)50)/255.0f, ((u8)255)/255.0f)
+/// converts float vector to hex color
+#define RGBAFToHex(VEC4) {(u8)(VEC4.x*255), (u8)(VEC4.y*255), (u8)(VEC4.z*255), (u8)(VEC4.w*255)}
+
+namespace ougge::gui {
+
+#define default_font_path "fonts/DroidSans.ttf"
+
+class MainWindow {
+public:
+    i32 fps_max = 60;
+    f32 default_font_size = 14.0f;
+    ImVec4 clear_color = RGBAHexToF(35,35,50,255);
+    SDL_Window* sdl_window = nullptr;
+    SDL_Renderer* sdl_renderer = nullptr;
+
+private:
+    bool show_debug_window = true;
+    bool show_demo_window = false;
+    bool show_metrics_window = false;
+
+public:
+    void open(const std::string& window_title, resources::ResourceManager& resourceManager);
+    void close();
+
+    /// process io events happened since previous frame
+    void pollEvents(bool* loopRunning);
+    void beginFrame();
+    void endFrame();
+
+    f32 getDPI();
+private:
+    void draw_debug_window();
+    void draw_bg_window();
+};
+
+}
diff --git a/src/main.cpp b/src/main.cpp
index 8d4c823..cf5dd7d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,63 +1,65 @@
-#define SDL_MAIN_HANDLED
-#include <iostream>
-#include <iomanip>
-#include "common/UsefulException.hpp"
-#include "common/ougge_format.hpp"
-#include "Engine.hpp"
-#include "gui/gui.hpp"
-
-using namespace ougge;
-
-void drawTutel(Engine& engine){
-    resources::Texture& tutel = engine.textures.getOrCreate("tutel.png", engine.mainWindow.sdl_renderer);
-    resources::SDL_RenderCopyExF_Params params;
-    params.target_section = SDL_FRectConstruct(100, 100, 400, 400);
-    static i32 si = 1;
-    params.rotation_angle = M_PI_4 * (si++ / engine.mainWindow.fps_max);
-    tutel.render(params);
-}
-
-int main(int argc, const char** argv){
-    try {
-        resources::init();
-        std::cout<<"initialized resource loader"<<std::endl;
-        
-        Engine engine;
-        std::cout<<"initialized mono jit runtime"<<std::endl;
-        engine.init();
-        std::cout<<"initialized game engine"<<std::endl;
-        
-        game::GameObject& exampleObj = engine.createGameObject();
-        std::string componentClassName = "Ougge.ExampleComponent";
-        if(!engine.tryCreateComponent(exampleObj, componentClassName))
-            throw UsefulException(ougge_format("couldn't create component '%s'", componentClassName.c_str()));
-        
-        std::cout<<"created ExampleObject"<<std::endl;
-        
-        engine.updateCallback = [&engine](f64 deltaTime) -> void {
-            drawTutel(engine);
-        };
-        
-        engine.openMainWindow("ougge");
-        std::cout<<"created sdl window"<<std::endl;
-        engine.startLoop();
-        std::cout<<"sdl window has been cosed"<<std::endl;
-    }
-    catch(const std::exception& e){
-        std::cerr<<"Catched exception: "<<e.what()<<std::endl;
-        return -1;
-    }
-    catch(const char* cstr){
-        std::cerr<<"Catched error message (const char*): "<<cstr<<std::endl;
-        return -1;
-    }
-    catch(const std::string& str){
-        std::cerr<<"Catched error message (std::string): "<<str<<std::endl;
-        return -1;
-    }
-    catch(...){
-        std::cerr<<"Catched unknown error"<<std::endl;
-        return -1;
-    }
-    return 0;
-}
+#define SDL_MAIN_HANDLED
+#include <iostream>
+#include <iomanip>
+#include "common/UsefulException.hpp"
+#include "common/ougge_format.hpp"
+#include "Engine.hpp"
+#include "gui/gui.hpp"
+
+using namespace ougge;
+
+void drawTutel(Engine& engine){
+    resources::Texture* tutel = engine.textures.tryGetOrCreate("tutel.png", engine.mainWindow.sdl_renderer);
+    if(tutel == nullptr){
+        throw new UsefulException("couldn't find resource 'tutel.png'");
+    }
+    resources::SDL_RenderCopyExF_Params params;
+    params.target_section = SDL_FRectConstruct(100, 100, 400, 400);
+    static i32 si = 1;
+    params.rotation_angle = M_PI_4 * (si++ / engine.mainWindow.fps_max);
+    tutel->render(params);
+}
+
+int main(int argc, const char** argv){
+    try {
+        std::cout<<"initialized resource loader"<<std::endl;
+        
+        Engine engine;
+        std::cout<<"initialized mono jit runtime"<<std::endl;
+        engine.init();
+        std::cout<<"initialized game engine"<<std::endl;
+        
+        game::GameObject& exampleObj = engine.createGameObject();
+        std::string componentClassName = "Ougge.ExampleComponent";
+        if(!engine.tryCreateComponent(exampleObj, componentClassName))
+            throw UsefulException(ougge_format("couldn't create component '%s'", componentClassName.c_str()));
+        
+        std::cout<<"created ExampleObject"<<std::endl;
+        
+        engine.updateCallback = [&engine](f64 deltaTime) -> void {
+            drawTutel(engine);
+        };
+        
+        engine.openMainWindow("ougge");
+        std::cout<<"created sdl window"<<std::endl;
+        engine.startLoop();
+        std::cout<<"sdl window has been cosed"<<std::endl;
+    }
+    catch(const std::exception& e){
+        std::cerr<<"Catched exception: "<<e.what()<<std::endl;
+        return -1;
+    }
+    catch(const char* cstr){
+        std::cerr<<"Catched error message (const char*): "<<cstr<<std::endl;
+        return -1;
+    }
+    catch(const std::string& str){
+        std::cerr<<"Catched error message (std::string): "<<str<<std::endl;
+        return -1;
+    }
+    catch(...){
+        std::cerr<<"Catched unknown error"<<std::endl;
+        return -1;
+    }
+    return 0;
+}
diff --git a/src/resources/MemorySteam.cpp b/src/resources/MemorySteam.cpp
new file mode 100644
index 0000000..fea56e5
--- /dev/null
+++ b/src/resources/MemorySteam.cpp
@@ -0,0 +1,40 @@
+#include "MemoryStream.hpp"
+
+class MemoryStreamBuf : public std::streambuf {
+public:
+    MemoryStreamBuf(void* p, const std::size_t n);
+
+    virtual std::istream::pos_type seekoff(
+        std::istream::off_type off,
+        std::ios_base::seekdir dir,
+        std::ios_base::openmode which);
+};
+
+MemoryStreamBuf::MemoryStreamBuf(void* _p, const std::size_t n){
+    char* p=(char*)_p;
+    setg(p, p, p + n);
+    setp(p, p + n);
+}
+
+std::istream::pos_type MemoryStreamBuf::seekoff(
+    std::istream::off_type off,
+    std::ios_base::seekdir dir,
+    std::ios_base::openmode which)
+{
+    if (dir == std::ios_base::cur)
+        gbump(off);
+    else if (dir == std::ios_base::end)
+        setg(eback(), egptr() + off, egptr());
+    else if (dir == std::ios_base::beg)
+        setg(eback(), eback() + off, egptr());
+    return gptr() - eback();
+}
+
+
+MemoryStreamRead::MemoryStreamRead(const void* p, const std::size_t n)
+    : std::istream(new MemoryStreamBuf((void*)p, n))
+{}
+
+MemoryStreamRead::~MemoryStreamRead(){
+    delete rdbuf();
+}
diff --git a/src/resources/MemoryStream.hpp b/src/resources/MemoryStream.hpp
new file mode 100644
index 0000000..0f1ced9
--- /dev/null
+++ b/src/resources/MemoryStream.hpp
@@ -0,0 +1,8 @@
+#include <iostream>
+
+class MemoryStreamRead : public std::istream {
+public:
+    MemoryStreamRead(const void* p, const std::size_t n);
+
+    virtual ~MemoryStreamRead();
+};
\ No newline at end of file
diff --git a/src/resources/fonts.cpp b/src/resources/fonts.cpp
index 3ce4b5b..96cde0f 100644
--- a/src/resources/fonts.cpp
+++ b/src/resources/fonts.cpp
@@ -1,7 +1,4 @@
-#include <imgui.h>
-#include "resources.hpp"
-#include <cstdio>
-#include <cstring>
+#include "fonts.hpp"
 
 namespace ougge::resources {
 
@@ -16,17 +13,16 @@ ImFont* ImFont_LoadFromFile(const std::string& file_path, f32 font_size, f32 dpi
     return io.Fonts->AddFontFromFileTTF(file_path.c_str(), font_size, nullptr, glyph_ranges);
 }
 
-ImFont* ImFont_LoadFromResource(const std::string& font_name, f32 font_size, f32 dpi){
+ImFont* ImFont_LoadFromResource(ResourceFactory* res, f32 font_size, f32 dpi){
     ImGuiIO& io = ImGui::GetIO();
     font_size *= dpi;
     ImFontConfig font_cfg = ImFontConfig();
-    std::sprintf(font_cfg.Name, "%s %ipx", font_name.c_str(), (i32)font_size);
+    std::sprintf(font_cfg.Name, "%s %ipx", res->path.c_str(), (i32)font_size);
     
-    auto& res = getResource("fonts/" + font_name + ".ttf");
-    char* font_data = new char[res.size]; 
-    res.openStream()->read(font_data, res.size);
+    char* font_data = new char[res->size]; 
+    res->openStream()->read(font_data, res->size);
 
-    return io.Fonts->AddFontFromMemoryTTF((void*)(font_data), res.size,
+    return io.Fonts->AddFontFromMemoryTTF((void*)(font_data), res->size,
         font_size, &font_cfg, glyph_ranges);
 }
 
diff --git a/src/resources/fonts.hpp b/src/resources/fonts.hpp
index 22bf712..6ab1b08 100644
--- a/src/resources/fonts.hpp
+++ b/src/resources/fonts.hpp
@@ -1,12 +1,13 @@
 #pragma once
 
-#include "imgui.h"
+#include <imgui.h>
 #include "../common/std.hpp"
+#include "resources.hpp"
 
 namespace ougge::resources {
 
 ImFont* ImFont_LoadFromFile(const std::string& file_path, f32 font_size, f32 dpi);
 
-ImFont* ImFont_LoadFromResource(const std::string& font_name, f32 font_size, f32 dpi);
+ImFont* ImFont_LoadFromResource(ResourceFactory* res, f32 font_size, f32 dpi);
 
 }
diff --git a/src/resources/resources.cpp b/src/resources/resources.cpp
index a996571..5591582 100644
--- a/src/resources/resources.cpp
+++ b/src/resources/resources.cpp
@@ -4,45 +4,22 @@
 #include "../common/ougge_format.hpp"
 #include "resources.hpp"
 #include "embedded_resources.h"
-
+#include "MemoryStream.hpp"
 
 namespace ougge::resources {
 
-Resource::Resource(const std::string& path, const std::size_t size, StreamFactoryMethod open_read_steam_func)
+ResourceFactory::ResourceFactory(const std::string& path, const std::size_t size, StreamFactoryMethod open_read_steam_func)
   : path(path), size(size), openStream(open_read_steam_func)
 {}
 
-MemoryStreamBuf::MemoryStreamBuf(void* _p, const std::size_t n){
-    char* p=(char*)_p;
-    setg(p, p, p + n);
-    setp(p, p + n);
-}
 
-std::istream::pos_type MemoryStreamBuf::seekoff(
-    std::istream::off_type off,
-    std::ios_base::seekdir dir,
-    std::ios_base::openmode which)
-{
-    if (dir == std::ios_base::cur)
-        gbump(off);
-    else if (dir == std::ios_base::end)
-        setg(eback(), egptr() + off, egptr());
-    else if (dir == std::ios_base::beg)
-        setg(eback(), eback() + off, egptr());
-    return gptr() - eback();
-}
+std::shared_ptr<ResourceMap> ResourceManager::_embeddedResourcesMap;
 
-MemoryStreamRead::MemoryStreamRead(const void* p, const std::size_t n)
-    : std::istream(new MemoryStreamBuf((void*)p, n))
-{}
+void ResourceManager::loadEmbeddedResources(){
+    if(_embeddedResourcesMap != nullptr)
+        return;
 
-MemoryStreamRead::~MemoryStreamRead(){
-    delete rdbuf();
-}
-
-static std::unordered_map<std::string, Resource>* _resourceMap = nullptr;
-
-void loadEmbeddedresources(){
+    _embeddedResourcesMap = std::make_shared<ResourceMap>();
     for(int i = 0; i < EmbeddedResource_table_count; i++){
         const EmbeddedResource& e = EmbeddedResource_table[i];
         std::cout <<"loading resource '" << e.path << "' " 
@@ -52,43 +29,36 @@ void loadEmbeddedresources(){
             return std::make_unique<MemoryStreamRead>(e.data, e.size); 
         };
 
-        auto r = _resourceMap->emplace(e.path, 
-            Resource(e.path, e.size, embedded_resource_factory));
+        auto r = _embeddedResourcesMap->emplace(e.path, 
+            ResourceFactory(e.path, e.size, embedded_resource_factory));
         if(!r.second)
             throw UsefulException(ougge_format("can't load duplicate resource '%s'", e.path));
     }
-}
-
-void init(){
-    if(_resourceMap != nullptr)
-        throw UsefulException("resource has been initialized already");
-    _resourceMap = new std::unordered_map<std::string, Resource>();
-    loadEmbeddedresources();
-}
-
-Resource& getResource(const std::string& path){
-    auto it = _resourceMap->find(path);
-    if(it == _resourceMap->end())
-        throw UsefulException(ougge_format("can't find resource '%s'", path.c_str()));
-    return it->second;
-}
-
-std::string formatSizeHumanReadable(std::size_t b){
-    std::stringstream ss;
-    ss.precision(3);
-    std::size_t k = b / 1024;
-    std::size_t m = k / 1024;
-    std::size_t g = m / 1024;
     
-    if(g)
-        ss<<m / 1024.0f<<'G';
-    else if(m)
-        ss<<k / 1024.0f<<'M';
-    else if(k)
-        ss<<b / 1024.0f<<'K';
-    else ss<<b;
+    _resourceMaps.push_back(_embeddedResourcesMap);
+}
 
-    return ss.str();
+ResourceManager::ResourceManager(){
+    loadEmbeddedResources();
+}
+
+ResourceFactory* ResourceManager::tryGetResource(const std::string& path){
+    // reverse iteration of linked list
+    auto map_list_iterator = _resourceMaps.end();
+    while(map_list_iterator != _resourceMaps.begin()){
+        --map_list_iterator;
+        auto map = *map_list_iterator;
+
+        auto resource_iterator = map->find(path);
+        
+        // resource not found
+        if(resource_iterator == map->end())
+            return nullptr;
+        
+        return &resource_iterator->second;
+    }
+
+    return nullptr;
 }
 
 }
diff --git a/src/resources/resources.hpp b/src/resources/resources.hpp
index 3b266df..2e6d8e6 100644
--- a/src/resources/resources.hpp
+++ b/src/resources/resources.hpp
@@ -4,60 +4,71 @@
 #include <iostream>
 #include <functional>
 #include <unordered_map>
+#include <memory>
+#include <list>
 
 namespace ougge::resources {
 
-// call this in main()
-void init();
-
-std::string formatSizeHumanReadable(std::size_t byte_n);
-
-class Resource {
+class ResourceFactory {
 public:
     const std::string path;
     const std::size_t size;
 
     using StreamFactoryMethod = std::function< std::unique_ptr<std::istream> () >;
 
-    Resource(const std::string& path, const std::size_t size, StreamFactoryMethod open_read_steam_func);
+    ResourceFactory(const std::string& path, const std::size_t size, StreamFactoryMethod open_read_steam_func);
 
     const StreamFactoryMethod openStream;
 };
 
-class MemoryStreamBuf : public std::streambuf {
+using ResourceMap = std::unordered_map<std::string, ResourceFactory>;
+
+class ResourceManager {
+    std::list<std::shared_ptr<ResourceMap>> _resourceMaps;
+    static std::shared_ptr<ResourceMap> _embeddedResourcesMap;
+    void loadEmbeddedResources();
+
 public:
-    MemoryStreamBuf(void* p, const std::size_t n);
+    ResourceManager();
 
-    virtual std::istream::pos_type seekoff(
-        std::istream::off_type off,
-        std::ios_base::seekdir dir,
-        std::ios_base::openmode which);
+    void addResourceMap(std::shared_ptr<ResourceMap> m);
+    
+    std::shared_ptr<ResourceMap> loadResouceMap();
+    void removeResourceMap();
+
+    ResourceFactory* tryGetResource(const std::string& path);
 };
 
-class MemoryStreamRead : public std::istream {
-public:
-    MemoryStreamRead(const void* p, const std::size_t n);
-
-    virtual ~MemoryStreamRead();
-};
-
-Resource& getResource(const std::string& path);
-
 /// @brief stores requested resources in memory
-/// @tparam T must implement constructor `T(const Resource&, ...)`
+/// @tparam T must implement constructor `T(ResourceFactory*, ...)`
 template<class T>
 class CacheStorage {
     std::unordered_map<std::string, T> _map;
+    ResourceManager* _resourceManager;
 
 public:
+    CacheStorage(ResourceManager*);
+    CacheStorage(CacheStorage&&) = delete;
+    CacheStorage(const CacheStorage&) = delete;
+
     template<typename... TCtorArgs>
-    T& getOrCreate(const std::string& name, TCtorArgs&&... ctor_args){
+    T* tryGetOrCreate(const std::string& name, TCtorArgs&&... ctor_args){
         auto it = _map.find(name);
         if(it != _map.end())
-            return it->second;
-        auto& res = getResource(name);
+            return &it->second;
+        
+        ResourceFactory* res = _resourceManager->tryGetResource(name);
+        if(res == nullptr)
+            return nullptr;
+        
         auto e = _map.emplace(name, T(res, ctor_args...));
-        return e.first->second;
+        return &e.first->second;
     }
 };
+
+
+template <class T> inline CacheStorage<T>::CacheStorage(ResourceManager* resourceManager)
+    : _resourceManager(resourceManager)
+{}
+
 }
diff --git a/src/resources/textures.cpp b/src/resources/textures.cpp
index 2476a2b..ec6b672 100644
--- a/src/resources/textures.cpp
+++ b/src/resources/textures.cpp
@@ -4,8 +4,8 @@
 
 namespace ougge::resources {
 
-Texture::Texture(const Resource& r, SDL_Renderer* renderer) 
-    : Texture(*r.openStream(), r.size, renderer)
+Texture::Texture(ResourceFactory* r, SDL_Renderer* renderer) 
+    : Texture(*r->openStream(), r->size, renderer)
 {}
 
 Texture::Texture(std::istream& s, size_t size, SDL_Renderer* renderer)
diff --git a/src/resources/textures.hpp b/src/resources/textures.hpp
index 2c05b7c..4869f77 100644
--- a/src/resources/textures.hpp
+++ b/src/resources/textures.hpp
@@ -33,7 +33,7 @@ struct Texture {
     i32 w;
     i32 h;
 
-    Texture(const Resource& r, SDL_Renderer* renderer);
+    Texture(ResourceFactory* r, SDL_Renderer* renderer);
     Texture(std::istream& s, size_t size, SDL_Renderer* renderer);
 
     void render(const SDL_FRect& target_section);