diff --git a/Makefile b/Makefile
index ea56c282..d1d47ed4 100644
--- a/Makefile
+++ b/Makefile
@@ -1,11 +1,15 @@
 # This Makefile works for Mac OS X (El Capitan), MinGW, and Linux.
+# 
+# Environmental vairables:
+#   If you want to build with Glew, set
+#     HYPERROGUE_USE_GLEW=1
+#   If you want to use libpng, set
+#     HYPERROGUE_USE_PNG=1
 #
 # For Mac OS X:
-#   Run "brew install sdl" to install SDL in /usr/local.
-#   Run "brew install sdl_gfx".
-#   Run "brew install sdl_mixer".
-#   Run "brew install sdl_ttf".
-#   Run "make" to build HyperRogue as ./hyperrogue.
+#   Run `brew install sdl12-compat sdl_gfx sdl_mixer sdl_ttf`
+#   Run `brew install glew libpng` to install the optional dependencies
+#   Run `make` to build HyperRogue as `./hyperrogue`.
 #
 # For MSYS2 and MinGW-w64:
 #   You might need to run commands such as "pacman -S mingw-w64-x86_64-SDL"
@@ -68,9 +72,10 @@ ifeq (${OS},mingw)
 endif
 
 ifeq (${OS},osx)
-  CXXFLAGS_EARLY += -DMAC -I/usr/local/include
+  HOMEBREW_PREFIX := $(shell brew --prefix)
+  CXXFLAGS_EARLY += -DMAC -I$(HOMEBREW_PREFIX)/include -I$(HOMEBREW_PREFIX)/include/SDL
   EXE_EXTENSION :=
-  LDFLAGS_EARLY += -L/usr/local/lib
+  LDFLAGS_EARLY += -L$(HOMEBREW_PREFIX)/lib
   LDFLAGS_GL := -framework AppKit -framework OpenGL
   LDFLAGS_GLEW := -lGLEW
   LDFLAGS_PNG := -lpng
diff --git a/README.md b/README.md
index a1b2bc0d..6ad2951a 100644
--- a/README.md
+++ b/README.md
@@ -62,15 +62,13 @@ On Linux with apt-get:
 
 On macOS with Homebrew:
 
-```brew install sdl sdl_ttf sdl_gfx sdl_mixer glew```
-
-macOS users might also have to edit /usr/local/include/SDL/SDL_gfxPrimitives.h at line 38 to use quote include.
+```brew install sdl sdl_ttf sdl_gfx sdl_mixer glew libpng```
 
 ### Building HyperRogue from source ###
 ```
 git clone https://github.com/zenorogue/hyperrogue.git hyperrogue
 cd hyperrogue
-make
+HYPERROGUE_USE_GLEW=1 HYPERROGUE_USE_PNG=1 make
 ```
 
 The `mymake` program builds HyperRogue in parts. It takes longer than the method shown above, but it uses significantly less memory during compilation, and when you change something, `mymake` will only recompile the changed file.