Replace GLEW with GLAD and actually check OpenGL 3.0 requirement

README.md

@@ -40,7 +40,7 @@ make sure your working directory is set to the main directory (the root folder o
 then run `make` to compile the binaries.
 
 Several dependencies are required to build on Linux, including: libpng, zlib,
-GLEW, GLU, freetype2, libvorbisfile, libvorbis, libogg, libopenal, libbz2,
+GLU, freetype2, libvorbisfile, libvorbis, libogg, libopenal, libbz2,
 libXRandR, and libcurl.
 
 

source/game/compat/gl.h

@@ -1,3 +1,8 @@
 #pragma once
-#include <GL/glew.h>
+#include "glad/gl.h"
+#if defined(__APPLE__) && defined(__MACH__)
+#  include <OpenGL/glu.h>
+#else
+#  include <GL/glu.h>
+#endif
 #include "GLFW/glfw3.h"