Stuff I've fixed so far.

src/dawnopengl/scene/components/display/material/SimpleTexturedMaterial.cpp

@@ -4,6 +4,7 @@
 // https://opensource.org/licenses/MIT
 
 #include "SimpleTexturedMaterial.hpp"
+#include "game/DawnGame.hpp"
 
 using namespace Dawn;
 
@@ -13,5 +14,5 @@ SimpleTexturedMaterial::SimpleTexturedMaterial(SceneItem *i) :
 }
 
 Shader * SimpleTexturedMaterial::getShader() {
-  return this->shader;
+  return &this->getGame()->renderManager.simpleShader;
 }

src/dawnopengl/scene/components/display/material/SimpleTexturedMaterial.hpp

@@ -4,13 +4,11 @@
 // https://opensource.org/licenses/MIT
 
 #pragma once
-#include "display/shader/SimpleTexturedShader.hpp"
 #include "scene/components/display/Material.hpp"
 
 namespace Dawn {
   class SimpleTexturedMaterial : public Material {
     public:
-      SimpleTexturedShader *shader = nullptr;
       Texture *texture = nullptr;
       struct Color color = COLOR_WHITE;