diff --git a/module00/ex03/main.c b/module00/ex03/main.c
new file mode 100644
index 0000000..f219aa9
--- /dev/null
+++ b/module00/ex03/main.c
@@ -0,0 +1,45 @@
+#include <avr/io.h>
+#include <util/delay.h>
+
+#define SET(REGISTER, BIT)			REGISTER |= 1 << BIT
+#define CLEAR(REGISTER, BIT)		REGISTER &= ~(1 << BIT)
+#define TEST(REGISTER, BIT)			REGISTER & 1 << BIT
+#define TEST_PIN(PORT, BIT)			PIN ## PORT & 1 << BIT
+#define TOGGLE(REGISTER, BIT)		REGISTER ^= 1 << BIT
+#define TOGGLE_PIN(PORT, BIT)		PIN ## PORT |= 1 << BIT
+#define MODE_INPUT(PORT, BIT)		CLEAR(DDR ## PORT, BIT)
+#define MODE_OUTPUT(PORT, BIT)		SET(DDR ## PORT, BIT)
+#define IS_PIN_SET(PORT, BIT)		(TEST_PIN(PORT, BIT)) == 0
+#define IS_PIN_CLEAR(PORT, BIT)		(TEST_PIN(PORT, BIT)) == 1
+
+#define D1 0
+#define D2 1
+#define D3 2
+#define D4 4
+#define SW1 2
+#define SW2 4
+
+#define ON	1
+#define OFF	0
+#define SWITCH(state)	state = (state == ON) ? OFF : ON;
+
+int main() {
+
+	// FLASHING
+	
+	MODE_OUTPUT(B, D1);
+	MODE_INPUT(D, SW1);
+	int state = OFF;
+	while(1) {
+		if (IS_PIN_SET(D, SW1)) {
+			SWITCH(state);
+ 		}
+		if (state) {
+			SET(PORTB, D1);
+		}
+		else {
+			CLEAR(PORTB, D1);
+		}
+		_delay_ms(100);
+	}
+}
\ No newline at end of file