diff --git a/include/RenderManager.h b/include/RenderManager.h
index 9d60efc..86aa614 100644
--- a/include/RenderManager.h
+++ b/include/RenderManager.h
@@ -8,10 +8,20 @@ class RenderManager {
 public:
 	RenderManager() {};
 
+	/*
+	 * Remove an object from the list of objects to be rendered
+	 * \param renderObject The object to be removed
+	 * \sa RenderObject
+	 */
 	void remove(RenderObject* obj);
+	/*
+	 * Add an object to be rendered
+	 * \param renderObject The object to be rendered
+	 * \sa RenderObject
+ 	 */
 	void add(RenderObject* obj);
 
-	void renderAll();
+	void renderAll(); //!< Render all objects. If the list has been modified, sorts it based on z-index first
 
 private:
 	std::vector<RenderObject*> renderObjects;
diff --git a/include/RenderObject.h b/include/RenderObject.h
index 5e7de99..ba4b929 100644
--- a/include/RenderObject.h
+++ b/include/RenderObject.h
@@ -5,13 +5,14 @@ class RenderManager;
 class RenderObject
 {
 public:
-	virtual void draw() {}
+	virtual void draw() = 0;
 
 	RenderObject(int zIndex, RenderManager& renderManager);
 	~RenderObject();
 
 	int getZIndex() { return this->zIndex; };
 
+	//! Comparitor to compare two ptr based on z-index
 	struct ZIndexComparator {
 		bool operator()(RenderObject const *lhs, RenderObject const *rhs ) const {
     		return lhs->zIndex < rhs->zIndex;
diff --git a/src/RenderManager.cpp b/src/RenderManager.cpp
index 634d389..dfa77f9 100644
--- a/src/RenderManager.cpp
+++ b/src/RenderManager.cpp
@@ -2,6 +2,7 @@
 #include "RenderObject.h"
 #include <algorithm>
 
+
 void RenderManager::renderAll()
 {
 	if (!this->isSorted) {