diff --git a/GL/glu.c b/GL/glu.c
index 2ed4444..9b2f48d 100644
--- a/GL/glu.c
+++ b/GL/glu.c
@@ -4,9 +4,9 @@
 /* Set the Perspective */
 void APIENTRY gluPerspective(GLdouble angle, GLdouble aspect,
                     GLdouble znear, GLdouble zfar) {
-    GLfloat fW, fH;
+    GLdouble fW, fH;
 
-    fH = tanf(angle * (M_PI / 360.0f)) * znear;
+    fH = tan(angle * (M_PI / 360.0)) * znear;
     fW = fH * aspect;
 
     glFrustum(-fW, fW, -fH, fH, znear, zfar);
diff --git a/samples/depth_funcs_alpha_testing/gl_png.c b/samples/depth_funcs_alpha_testing/gl_png.c
index 5415638..29becd4 100644
--- a/samples/depth_funcs_alpha_testing/gl_png.c
+++ b/samples/depth_funcs_alpha_testing/gl_png.c
@@ -14,178 +14,172 @@
 GLfloat global_diffuse[] = {1.0, 1.0, 1.0, 1.0};
 GLfloat global_ambient[] = {1.0, 1.0, 1.0, 1.0};
 
+static int decode_dtex(Image* image, FILE* file) {
+	struct {
+			char	id[4];	// 'DTEX'
+			GLushort	width;
+			GLushort	height;
+			GLuint		type;
+			GLuint		size;
+	} header;
+
+	fread(&header, sizeof(header), 1, file);
+
+	image->twiddled   = (header.type & (1 << 26)) < 1;
+	image->compressed = (header.type & (1 << 30)) > 0;
+	image->mipmapped  = (header.type & (1 << 31)) > 0;
+	GLuint format = (header.type >> 27) & 0b111;
+
+	image->data = (char *) malloc (header.size);
+	image->sizeX = header.width;
+	image->sizeY = header.height;
+	image->dataSize = header.size;
+
+	fread(image->data, image->dataSize, 1, file);
+	fclose(file);
+
+	if(image->compressed && image->twiddled) {
+		switch(format) {
+			case 0:
+				puts("Compressed & Twiddled - ARGB 1555");
+				if(image->mipmapped) {
+					image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_MIPMAP_TWID_KOS;
+				} else {
+					image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_TWID_KOS;
+				}
+				return 1;
+			
+			case 1:
+				puts("Compressed & Twiddled - RGB 565");
+				if(image->mipmapped) {
+					image->internalFormat = GL_COMPRESSED_RGB_565_VQ_MIPMAP_TWID_KOS;
+				} else {
+					image->internalFormat = GL_COMPRESSED_RGB_565_VQ_TWID_KOS;
+				}
+				return 1;
+			
+			case 2:
+				puts("Compressed & Twiddled - ARGB 4444");
+				if(image->mipmapped) {
+					image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_MIPMAP_TWID_KOS;
+				} else {
+					image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_TWID_KOS;
+				}
+				return 1;
+			
+		}
+	} else if (image->compressed) {
+		switch(format) {
+			case 0:
+				puts("Compressed - ARGB 1555");
+				if(image->mipmapped) {
+					image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_MIPMAP_KOS;
+				} else {
+					image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_KOS;
+				}
+				return 1;
+				
+			case 1:
+				puts("Compressed - RGB 565");
+				if(image->mipmapped) {
+					image->internalFormat = GL_COMPRESSED_RGB_565_VQ_MIPMAP_KOS;
+				} else {
+					image->internalFormat = GL_COMPRESSED_RGB_565_VQ_KOS;
+				}
+				return 1;
+				
+			case 2:
+				puts("Compressed - ARGB 4444");
+				if(image->mipmapped) {
+					image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_MIPMAP_KOS;
+				} else {
+					image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_KOS;
+				}
+				return 1;
+		}
+	} else {
+		switch (format) {
+			case 0:
+				puts("Uncompressed - ARGB 1555");
+				image->internalFormat = GL_ARGB1555_TWID_KOS;
+				image->transferFormat = GL_BGRA;
+				image->transferType   = GL_UNSIGNED_SHORT_1_5_5_5_REV_TWID_KOS;
+				return 1;
+				
+			case 1:
+				puts("Uncompressed - RGB 565");
+				image->internalFormat = GL_RGB565_TWID_KOS;
+				image->transferFormat = GL_RGB;
+				image->transferType   = GL_UNSIGNED_SHORT_5_6_5_TWID_KOS;
+				return 1;
+				
+			case 2:
+				puts("Uncompressed - ARGB 4444");
+				image->internalFormat = GL_ARGB4444_TWID_KOS;
+				image->transferFormat = GL_BGRA;
+				image->transferType   = GL_UNSIGNED_SHORT_4_4_4_4_REV_TWID_KOS;
+				return 1;
+		}
+	}
+	
+	fprintf(stderr, "Invalid texture format %u\n", header.type);
+	return 0;
+}
 
 int dtex_to_gl_texture(texture *tex, char* filename) {
     // Load Texture
-    Image *image;
+    Image image = { 0 };
 
-    // allocate space for texture
-    image = (Image *) malloc(sizeof(Image));
-    if (image == NULL) {
-				printf("No memory for .DTEX file\n");
-				return(0);
-    }
+	FILE* file = NULL;
 
-		FILE* file = NULL;
+	// make sure the file is there.
+	if ((file = fopen(filename, "rb")) == NULL)
+	{
+		printf("File not found");
+			return 0;
+	}
 
-		// make sure the file is there.
-		if ((file = fopen(filename, "rb")) == NULL)
-		{
-			printf("File not found");
-				return 0;
-		}
+	decode_dtex(&image, file);
 
-		struct {
-				char	id[4];	// 'DTEX'
-				GLushort	width;
-				GLushort	height;
-				GLuint		type;
-				GLuint		size;
-		} header;
-
-		fread(&header, sizeof(header), 1, file);
-
-		GLboolean twiddled = (header.type & (1 << 26)) < 1;
-		GLboolean compressed = (header.type & (1 << 30)) > 0;
-		GLboolean mipmapped = (header.type & (1 << 31)) > 0;
-		GLuint 		format = (header.type >> 27) & 0b111;
-
-		image->data = (char *) malloc (header.size);
-		image->sizeX = header.width;
-		image->sizeY = header.height;
-		image->dataSize = header.size;
-
-		GLuint expected = 2 * header.width * header.height;
-		GLuint ratio = (GLuint) (((GLfloat) expected) / ((GLfloat) header.size));
-
-		fread(image->data, image->dataSize, 1, file);
-		fclose(file);
-
-		if(compressed) {
-				printf("Compressed - ");
-				if(twiddled) {
-					printf("Twiddled - ");
-						switch(format) {
-								case 0: {
-										if(mipmapped) {
-												image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_MIPMAP_TWID_KOS;
-										} else {
-												image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_TWID_KOS;
-										}
-								} break;
-								case 1: {
-										if(mipmapped) {
-												image->internalFormat = GL_COMPRESSED_RGB_565_VQ_MIPMAP_TWID_KOS;
-										} else {
-												image->internalFormat = GL_COMPRESSED_RGB_565_VQ_TWID_KOS;
-										}
-								} break;
-								case 2: {
-										if(mipmapped) {
-												image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_MIPMAP_TWID_KOS;
-										} else {
-												image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_TWID_KOS;
-										}
-								}
-								break;
-								default:
-										fprintf(stderr, "Invalid texture format");
-										return 0;
-						}
-				} else {
-						switch(format) {
-								case 0: {
-										if(mipmapped) {
-												image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_MIPMAP_KOS;
-										} else {
-												image->internalFormat = GL_COMPRESSED_ARGB_1555_VQ_KOS;
-										}
-								} break;
-								case 1: {
-										if(mipmapped) {
-												image->internalFormat = GL_COMPRESSED_RGB_565_VQ_MIPMAP_KOS;
-										} else {
-												image->internalFormat = GL_COMPRESSED_RGB_565_VQ_KOS;
-										}
-								} break;
-								case 2: {
-										if(mipmapped) {
-												image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_MIPMAP_KOS;
-										} else {
-												image->internalFormat = GL_COMPRESSED_ARGB_4444_VQ_KOS;
-										}
-								}
-								break;
-								default:
-										fprintf(stderr, "Invalid texture format");
-										return 0;
-						}
-				}
-		} else {
-			printf("Uncompressed - ");
-			//printf("Color:%u -", format);
-				switch(format) {
-
-						case 0:
-								image->internalFormat = GL_UNSIGNED_SHORT_1_5_5_5_REV_TWID_KOS;
-								//image->internalFormat = GL_UNSIGNED_SHORT_1_5_5_5_REV;
-						break;
-						case 1:
-								image->internalFormat = GL_UNSIGNED_SHORT_5_6_5_REV;
-						break;
-						case 2:
-								image->internalFormat = GL_UNSIGNED_SHORT_4_4_4_4_REV;
-						break;
-			}
-		}
-		printf("\n");
-
-		// Create Texture
-		GLuint texture_id;
-    glGenTextures(1, &texture_id);
-    glBindTexture(GL_TEXTURE_2D, texture_id);   // 2d texture (x and y size)
-
-		GLint newFormat = format;
-		GLint colorType = GL_RGB;
-
-		if (image->internalFormat == GL_UNSIGNED_SHORT_1_5_5_5_REV_TWID_KOS ||
-				image->internalFormat == GL_UNSIGNED_SHORT_4_4_4_4_REV){
-					 newFormat = GL_BGRA;
-					 colorType = GL_RGBA;
-					 printf("Reversing RGBA\n");
-			}
-
-		if (image->internalFormat == GL_UNSIGNED_SHORT_5_6_5_REV){
-					 newFormat = GL_RGB;
-					 colorType = GL_RGB;
-					 printf("Reversing RGB\n");
-			}
+	// Create Texture
+	GLuint texture_id;
+	glGenTextures(1, &texture_id);
+	glBindTexture(GL_TEXTURE_2D, texture_id);   // 2d texture (x and y size)
 
+	if (image.compressed) {
+		glCompressedTexImage2D(GL_TEXTURE_2D, 0,
+			image.internalFormat, image.sizeX, image.sizeY,
+			0, image.dataSize, image.data);
+	} else {
 		glTexImage2D(GL_TEXTURE_2D, 0,
-			colorType, image->sizeX, image->sizeY, 0,
-			newFormat, image->internalFormat, image->data);
+			image.internalFormat, image.sizeX, image.sizeY, 0,
+			image.transferFormat, image.transferType, image.data);
+	}
 
-		tex->id = texture_id;
-		tex->w = image->sizeX;
-		tex->h = image->sizeY;
-		tex->u = 0.f;
-		tex->v = 0.f;
-		tex->a = tex->light = 1;
-		tex->color[0] = tex->color[1] = tex->color[2] = 1.0f;
-		tex->uSize = tex->vSize = 1.0f;
-		tex->xScale = tex->yScale = 1.0f;
-		tex->format = image->internalFormat;
-		tex->min_filter = tex->mag_filter = GL_NEAREST;
-		tex->blend_source = GL_SRC_ALPHA;
-		tex->blend_dest = GL_ONE_MINUS_SRC_ALPHA;
-		strcpy(tex->path, filename);
+	tex->id = texture_id;
+	tex->w = image.sizeX;
+	tex->h = image.sizeY;
+	tex->u = 0.f;
+	tex->v = 0.f;
+	tex->a = tex->light = 1;
+	tex->color[0] = tex->color[1] = tex->color[2] = 1.0f;
+	tex->uSize = tex->vSize = 1.0f;
+	tex->xScale = tex->yScale = 1.0f;
+	tex->format = image.internalFormat;
+	tex->min_filter = tex->mag_filter = GL_NEAREST;
+	tex->blend_source = GL_SRC_ALPHA;
+	tex->blend_dest = GL_ONE_MINUS_SRC_ALPHA;
+	strcpy(tex->path, filename);
+	
+	GLuint expected = 2 * image.sizeX * image.sizeY;
+	GLuint ratio = (GLuint) (((GLfloat) expected) / ((GLfloat) image.dataSize));
 
-		printf("Texture size: %lu x %lu\n", image->sizeX, image->sizeY);
-		printf("Texture ratio: %d\n", ratio);
-		printf("Texture size: %lu x %lu\n", image->sizeX, image->sizeY);
-		printf("Texture %s loaded\n", tex->path);
+	printf("Texture size: %lu x %lu\n", image.sizeX, image.sizeY);
+	printf("Texture ratio: %d\n", ratio);
+	printf("Texture size: %lu x %lu\n", image.sizeX, image.sizeY);
+	printf("Texture %s loaded\n", tex->path);
 
-		return(1);
+	return(1);
 }
 
 void draw_textured_quad(texture *tex) {
diff --git a/samples/depth_funcs_alpha_testing/gl_png.h b/samples/depth_funcs_alpha_testing/gl_png.h
index 29b312f..4b16eec 100644
--- a/samples/depth_funcs_alpha_testing/gl_png.h
+++ b/samples/depth_funcs_alpha_testing/gl_png.h
@@ -29,8 +29,8 @@ typedef struct Image {
     unsigned long sizeX;
     unsigned long sizeY;
     char 					*data;
-    GLenum 				internalFormat;
-    GLboolean 		mipmapped;
+    GLenum 				internalFormat, transferFormat, transferType;
+    unsigned int	mipmapped, compressed, twiddled;
     unsigned int 	dataSize;
 } Image;
 
diff --git a/samples/depth_funcs_alpha_testing/main.c b/samples/depth_funcs_alpha_testing/main.c
index 517d6a0..257b093 100644
--- a/samples/depth_funcs_alpha_testing/main.c
+++ b/samples/depth_funcs_alpha_testing/main.c
@@ -88,7 +88,7 @@ void DrawGLScene()
     glLoadIdentity();
     glTranslated(-1 , -1, -5);
     glDepthFunc(GL_LESS);
-    glEnable(GL_DEPTH_FUNC);
+    glEnable(GL_DEPTH_TEST);
 
     for (int i = 0; i < 5; i++) {
       glTranslated(0.5, 0, -0.2);