diff --git a/Makefile b/Makefile
index ddde8fb..5ba19c3 100644
--- a/Makefile
+++ b/Makefile
@@ -1,21 +1,24 @@
 
-SHELL = /bin/sh
-CXX = g++
+SHELL := /bin/sh
+CXX := g++
 # NOTE: have to set -O or -O1 here to get warnings for uninitialized variables
-CXXFLAGS = -std=c++11 -g -ggdb3 -Wall -O -Wall -Wuninitialized \
+CXXFLAGS := -std=c++11 -g -ggdb3 -Wall -O -Wall -Wuninitialized \
 	-Iinclude \
 	-I/usr/include/SDL2 \
 	-Iext/stb_libs \
 	-Iext/tinygltf
-EXAMPLEDIR = examples
-OBJDIR = build
-SRCDIR = src
-LIBNAME = libTangerine.a
-
-SOURCES = $(wildcard $(SRCDIR)/*.cpp)
-OBJECTS = $(patsubst $(SRCDIR)/%.cpp, $(OBJDIR)/%.o, $(SOURCES))
-NDBG_SOURCES = $(wildcard $(SRCDIR)/*.cc)
-NDBG_OBJS = $(patsubst $(SRCDIR)/%.cc, $(OBJDIR)/%.o, $(NDBG_SOURCES))
+EXAMPLEDIR := examples
+OBJDIR := build
+SRCDIR := src
+LIBNAME := libTangerine.a
+
+# NOTE: optional library settings
+CXXFLAGS += -DTANGERINE_GL_DEBUG_QUIET
+
+SOURCES := $(wildcard $(SRCDIR)/*.cpp)
+OBJECTS := $(patsubst $(SRCDIR)/%.cpp, $(OBJDIR)/%.o, $(SOURCES))
+NDBG_SOURCES := $(wildcard $(SRCDIR)/*.cc)
+NDBG_OBJS := $(patsubst $(SRCDIR)/%.cc, $(OBJDIR)/%.o, $(NDBG_SOURCES))
 
 
 all: mkdirs $(LIBNAME)
diff --git a/include/tangerine.h b/include/tangerine.h
index 34527ef..52b1e88 100644
--- a/include/tangerine.h
+++ b/include/tangerine.h
@@ -75,6 +75,11 @@
 
 #include <SDL2/SDL.h>
 
+
+// NOTE: optional compile-time defines:
+// 	TANGERINE_GL_DEBUG_QUIET  disable extra debug messages from openGL
+
+
 #include "asset.h"
 #include "camera.h"
 #include "entity.h"
@@ -86,13 +91,6 @@
 #include "util.h"
 
 
-// NOTE: can set TANGERINE_GL_DEBUG_QUIET in your application to disable extra
-// 	debug messages from openGL
-#ifndef TANGERINE_GL_DEBUG_QUIET
-	#define TANGERINE_GL_DEBUG_NOISY
-#endif
-
-
 struct SDLHandles
 {
 	SDL_Window* window;
diff --git a/src/shader.cpp b/src/shader.cpp
index edde8cb..2633b79 100644
--- a/src/shader.cpp
+++ b/src/shader.cpp
@@ -12,7 +12,6 @@
 #include "asset.h"
 #include "dumbLog.h"
 #include "dummy_shader.h"
-#define GL_DEBUG_IMPLEMENTATION
 #include "GLDebug.h"
 #include "shader.h"
 #include "util.h"
diff --git a/src/tangerine.cpp b/src/tangerine.cpp
index 5e4eb21..9fe0bea 100644
--- a/src/tangerine.cpp
+++ b/src/tangerine.cpp
@@ -7,6 +7,8 @@
 #include "tangerine.h"
 #define UTIL_IMPLEMENTATION
 #include "util.h"
+#define GL_DEBUG_IMPLEMENTATION
+#include "GLDebug.h"
 
 
 // forward declarations