--- Makefile.orig
+++ Makefile
@@ -23,8 +23,8 @@
 hasnoheader = main.h dos.h
 sourcefiles = $(filter-out $(hasnoheader),$(allfiles)) device.h mem.h roms.h types.h
 
-CC = g++
-cflags = -O3 -finline -frerun-loop-opt -Winline -fomit-frame-pointer `sdl-config --cflags`
+CC = $(CXX)
+cflags = $(CFLAGS) -finline -frerun-loop-opt -Winline -fomit-frame-pointer `sdl-config --cflags`
 libs = `sdl-config --libs` 
 
 #SDL_CFLAGS := $(shell sdl-config --cflags)
@@ -72,6 +72,9 @@
 prg.o : prg.cpp prg.h
 	$(CC) $(cflags) -c $< 
 
+serial.o : serial.cpp serial.h
+	$(CC) $(cflags) -c $< 
+
 sound.o : sound.cpp sound.h
 	$(CC) $(cflags) -c $<