--- Makefile.orig	2009-11-06 08:21:34.000000000 +1100
+++ Makefile	2011-02-09 14:37:01.000000000 +1100
@@ -9,22 +9,22 @@
 
 # User-definable stuff:
 
-CFLAGS=-Wall -O2
+CFLAGS?=-Wall -O2
 #DATA_PREFIX=$(PWD)/data/
-PREFIX=/usr/local
+PREFIX?=/usr/local
 MAN_PREFIX=$(PREFIX)
 BIN_PREFIX=$(PREFIX)/bin
 DATA_PREFIX=$(PREFIX)/share/defendguin/
-JOY=YES
+JOY?=YES
 
 
 # Other definitions:
 
 SDL_CFLAGS := $(shell sdl-config --cflags)
-SDL_LDFLAGS := $(shell sdl-config --libs) -L/usr/X11R6/lib
+SDL_LDFLAGS := $(shell sdl-config --libs)
 MIXER=-lSDL_mixer
 NOSOUNDFLAG=__SOUND
-CFLAGS=-Wall $(SDL_CFLAGS) -DDATA_PREFIX=\"$(DATA_PREFIX)\" -D$(NOSOUNDFLAG) \
+CFLAGS+=-Wall $(SDL_CFLAGS) -DDATA_PREFIX=\"$(DATA_PREFIX)\" -D$(NOSOUNDFLAG) \
 	-DJOY_$(JOY)
 SDL_LIB=$(SDL_LDFLAGS) $(MIXER)