diff --git a/Makefile b/Makefile
index 0503c93..e45edf9 100644
--- a/Makefile
+++ b/Makefile
@@ -9,7 +9,11 @@ MCU = atmega1284p
 QEMU_MACHINE_NAME = mega
 
 # Compiler flags
-CFLAGS = -std=c2x -Wall -Wno-array-bounds -mmcu=$(MCU) -DF_CPU=16000000UL -O3
+CFLAGS = -std=c99 -Wall -Wextra -Wpedantic -Wno-array-bounds -mmcu=$(MCU) \
+		 -DF_CPU=16000000UL -O2 -fno-common -ffunction-sections -fdata-sections
+
+# For debug
+CFLAGS += -g3 -DDEBUG
 
 # Source files
 SRCS = $(wildcard *.c)
@@ -34,6 +38,7 @@ $(TARGET).elf: $(OBJS)
 # Convert ELF to HEX
 $(TARGET).hex: $(TARGET).elf
 	avr-objcopy -O ihex -R .eeprom $(TARGET).elf $(TARGET).hex
+	avr-size $<
 
 # Flash the program
 flash: $(TARGET).hex