diff --git a/src/opengl.c b/src/opengl.c
index f82eaa1..3287ae9 100644
--- a/src/opengl.c
+++ b/src/opengl.c
@@ -1,3 +1,30 @@
+/**
+ * @file opengl.c
+ *
+ * @brief This file handles most of the more generic opengl functions.
+ *
+ * The main way to work with opengl in lephisto is to create glTextures and then
+ * use the blit functions to draw them on the screen. This system will handle
+ * relative and absolute positions.
+ *
+ * There are two coordinate systems: relative and absolute.
+ *
+ * Relative:
+ *    -- Everything is drawn relative to the player, if it doesn't fit on the
+ *       screen it is clipped.
+ *    -- Origin (0., 0.) would be ontop of the player.
+ *
+ * Absolute:
+ *    -- Everything is drawn in "screen coordinates".
+ *    -- (0., 0.) is bottom left.
+ *    -- (SCREEN_W, SCREEN_H) is top right.
+ *
+ * Note that the game actually uses a third type of coordinate for when using
+ * raw commands. In this third type, the (0., 0.) is actually in middle of the
+ * screen. (-SCREEN_W/2., -SCREEN_H/2.) is bottom left and
+ * (-SCREEN_W/2., -SCREEN_H/2.) is top right.
+ */
+
 #include <SDL/SDL.h>
 #include <SDL/SDL_image.h>
 #include "SDL_version.h"
diff --git a/src/opengl.h b/src/opengl.h
index 583d64c..4a6ae6a 100644
--- a/src/opengl.h
+++ b/src/opengl.h
@@ -7,15 +7,15 @@
 
 /* Recommended for compatibility bullshit. */
 #if SDL_BYTEORDER == SDL_BIG_ENDIAN
-#  define RMASK 0xff000000
-#  define GMASK 0x00ff0000
-#  define BMASK 0x0000ff00
-#  define AMASK 0x000000ff
+#  define RMASK 0xff000000  /**< Red bit mask. */
+#  define GMASK 0x00ff0000  /**< Green bit mask. */
+#  define BMASK 0x0000ff00  /**< Blue bit mask. */
+#  define AMASK 0x000000ff  /**< Alpha bit mask. */
 #else
-#  define RMASK 0x000000ff
-#  define GMASK 0x0000ff00
-#  define BMASK 0x00ff0000
-#  define AMASK 0xff000000
+#  define RMASK 0x000000ff  /**< Red bit mask. */
+#  define GMASK 0x0000ff00  /**< Green bit mask. */
+#  define BMASK 0x00ff0000  /**< Blue bit mask. */
+#  define AMASK 0xff000000  /**< Alpha bit mask. */
 #endif
 #define RGBAMASK RMASK,GMASK,BMASK,AMASK
 
@@ -33,8 +33,6 @@
 #define gl_has(f)           (gl_screen.flags & (f)) /**< Check for the flag. */
 
 /**
- * @struct glInfo
- *
  * @brief Store data about the current opengl environment.
  */
 typedef struct glInfo_ {
@@ -138,7 +136,7 @@ void gl_getSpriteFromDir(int* x, int* y, const glTexture* t, const double dir);
 void gl_screenshot(const char* filename);
 int SDL_savePNG(SDL_Surface* surface, const char* file);
 /*#if DEBUG == 1 */
-void gl_checkErr(void);
+void gl_checkErr(void); /**< Hack to ignore errors when debugging. */
 /*#else */
 /*#define gl_checkErr() */
 /*#endif */