Pick back up and comment

Clean placeholder code to get it running.
Add comments to clarify working, add TODOs in main,
add some references for the maths.

World.h

@@ -43,6 +43,13 @@ private:
     sf::Color ceilingColor;
 
     void fillColumn(sf::RenderWindow&, int column, float scale, sf::Color wallColor = sf::Color(127,127,127)) const;
+    /**
+     * Cast a ray from a given position and return the on-screen scale.
+     * @param originX Ray X origin
+     * @param originY Ray Y origin
+     * @param orientation Angle to cast to, in degrees
+     * @return Scale on the screen of the hit wall.
+     */
     float castRay(float originX, float originY, float orientation);
 };