diff --git a/CMakeLists.txt b/CMakeLists.txt
index 47f8f1e..7bd6082 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,14 @@
 cmake_minimum_required(VERSION 3.19 FATAL_ERROR)
 project(BillySheet LANGUAGES CXX C)
 
+find_package(OpenGL REQUIRED)
+
+set(PRECOMPILE_HEADERS
+	include/gui.hpp
+	include/gui_data.hpp
+	include/window.hpp
+	)
+
 set(SOURCE_HEADERS
 	include/imgui/imconfig.h
 	include/imgui/imgui.h
@@ -8,6 +16,9 @@ set(SOURCE_HEADERS
 	include/imgui/imgui_impl_opengl3.h
 	include/imgui/imgui_impl_opengl3_loader.h
 	include/imgui/imgui_internal.h
+	include/imgui/imstb_rectpack.h
+	include/imgui/imstb_textedit.h
+	include/imgui/imstb_truetype.h
 	include/gui.hpp
 	include/gui_data.hpp
 	include/window.hpp)
@@ -28,6 +39,17 @@ set(SOURCES
 	${SOURCE_HEADERS}
 	${SOURCE_FILES})
 
+find_program(CCACHE_FOUND ccache)
+if (CCACHE_FOUND)
+	message(STATUS "ccache found !")
+	set_property(GLOBAL PROPERTY C_COMPILER_LAUNCHER ccache)
+	set_property(GLOBAL PROPERTY C_LINKER_LAUNCHER ccache)
+	set_property(GLOBAL PROPERTY CXX_COMPILER_LAUNCHER ccache)
+	set_property(GLOBAL PROPERTY CXX_LINKER_LAUNCHER ccache)
+else ()
+	message(STATUS "ccache not found")
+endif ()
+
 option(BUILD_SHARED_LIBS "Build shared libraries" OFF)
 option(GLFW_BUILD_EXAMPLES "Build the GLFW example programs" OFF)
 option(GLFW_BUILD_TESTS "Build the GLFW test programs" OFF)
@@ -44,19 +66,66 @@ option(SPDLOG_NO_TLS "prevent spdlog from using thread local storage" ON)
 option(SPDLOG_NO_ATOMIC_LEVELS "prevent spdlog from using of std::atomic log levels (use only if your code never modifies log levels concurrently" ON)
 add_subdirectory(external/spdlog)
 
+set(COMPILE_FLAGS
+	-pipe
+	-march=skylake # change to native or your architecture.
+	-mtune=skylake # same as above
+	-mrdseed # be careful about this, this is linked to the x86 architecture.
+	-mrdrnd # same as above
+	-Wall
+	-Wextra
+	-Wpedantic
+	-pedantic
+	-ffunction-sections
+	-fdata-sections
+	-fuse-ld=gold
+	-funroll-loops
+	-fdevirtualize-at-ltrans
+	-fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-free
+	)
+set(LINKER_OPTIONS
+	-Wl,--sort-common,--as-needed,--gc-sections,--strip-all
+	-fuse-ld=gold
+	-fdevirtualize-at-ltrans
+	)
+
+set(LINKER_FLAGS
+	jemalloc
+	)
+
 add_executable(BillySheet ${SOURCES})
 
-target_include_directories(BillySheet PRIVATE include)
+target_include_directories(BillySheet PRIVATE include include/imgui)
 
-set_target_properties(BillySheet spdlog glfw PROPERTIES
+set_target_properties(BillySheet spdlog PROPERTIES
 					  CXX_STANDARD 17
 					  CXX_STANDARD_REQUIRED ON
 					  CXX_EXTENSIONS OFF
 					  INTERPROCEDURAL_OPTIMIZATION ON
-					  UNITY_BUILD ON)
-target_precompile_headers(BillySheet PRIVATE ${SOURCE_HEADERS})
+					  # UNITY_BUILD ON
+					  )
+set_target_properties(glfw PROPERTIES
+					  C_STANDARD 11
+					  C_STANDARD_REQUIRED ON
+					  C_EXTENSIONS OFF
+					  INTERPROCEDURAL_OPTIMIZATION ON
+					  # UNITY_BUILD ON
+					  )
+
+#target_precompile_headers(BillySheet PRIVATE ${PRECOMPILE_HEADERS})
 target_compile_definitions(BillySheet PRIVATE
 						   $<$<CONFIG:Debug>:_GLIBCXX_DEBUG>
 						   $<$<CONFIG:Debug>:SPDLOG_ACTIVE_LEVEL=SPDLOG_LEVEL_DEBUG>
 						   $<$<CONFIG:Release>:SPDLOG_ACTIVE_LEVEL=SPDLOG_LEVEL_ERROR>)
-target_link_libraries(BillySheet glfw spdlog)
+
+target_compile_options(spdlog PRIVATE ${COMPILE_FLAGS})
+target_compile_options(glfw PRIVATE ${COMPILE_FLAGS})
+target_compile_options(BillySheet PRIVATE ${COMPILE_FLAGS})
+
+target_link_options(spdlog PRIVATE ${LINKER_OPTIONS})
+target_link_options(glfw PRIVATE ${LINKER_OPTIONS})
+target_link_options(BillySheet PRIVATE ${LINKER_OPTIONS})
+
+target_link_libraries(spdlog PRIVATE ${LINKER_FLAGS})
+target_link_libraries(glfw PRIVATE ${LINKER_FLAGS})
+target_link_libraries(BillySheet glfw spdlog OpenGL::OpenGL ${LINKER_FLAGS})
diff --git a/README.md b/README.md
index 48b338e..4835699 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,12 @@
 This project is about to digitally control your character sheet from the book "La Forteresse du Chaudron Noir" from Bob Lennon.
 
 ## External dependencies
-All dependencies are inside the "external" directory. The followings are inside:
+Some dependencies are inside the "external" directory. The followings are inside:
 - GLFW: windowing
 - Spdlog: logging the app.
+
+The others are:
+- jemalloc
+- ccache
+- the gold linker
+- OpenGL
diff --git a/include/gui.hpp b/include/gui.hpp
index 7894976..21778dc 100644
--- a/include/gui.hpp
+++ b/include/gui.hpp
@@ -9,8 +9,6 @@ namespace gui {
 	public:
 		Gui() = delete;
 
-
-
 		~Gui() noexcept;
 	};
 }
diff --git a/include/gui_data.hpp b/include/gui_data.hpp
index edf1f25..dfe1471 100644
--- a/include/gui_data.hpp
+++ b/include/gui_data.hpp
@@ -1,13 +1,18 @@
 #ifndef BILLYSHEET_GUI_DATA_HPP
 #define BILLYSHEET_GUI_DATA_HPP
 
+#include "window.hpp"
+
 namespace gui {
 	class GuiData final {
 	private:
-//		GLFWwindow *window{ nullptr };
+		Window &window;
 
 	public:
 		GuiData() = delete;
+
+		explicit GuiData(Window &wwindow) : window(wwindow) {}
+
 		~GuiData() noexcept = default;
 	};
 }
diff --git a/src/gui_data.cpp b/src/gui_data.cpp
index adbb944..e3411e5 100644
--- a/src/gui_data.cpp
+++ b/src/gui_data.cpp
@@ -1,5 +1 @@
-//
-// Created by postaron on 08/01/2022.
-//
-
 #include "gui_data.hpp"
diff --git a/src/window.cpp b/src/window.cpp
index ccfe9ea..163122e 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -1,8 +1,13 @@
-#include <stdexcept>
 #include "window.hpp"
+#include <stdexcept>
+#include <spdlog/spdlog.h>
+
+static void glfwErrorCallback(int error, const char *message) {
+	spdlog::error("Error code {}: {}", error, message);
+}
 
 gui::Window::Window() {
-	glfwSetErrorCallback(nullptr);
+	glfwSetErrorCallback(glfwErrorCallback);
 	if (glfwInit() == GLFW_FALSE) {
 		throw std::runtime_error("GLFW init failed.");
 	}