diff --git a/module04/ex02/main.c b/module04/ex02/main.c
index b0dc699..17961b1 100644
--- a/module04/ex02/main.c
+++ b/module04/ex02/main.c
@@ -20,7 +20,13 @@
 //   13.2.6 : PCMSK2 – Pin Change Mask Register 2
 //    -> (1 << PCINT20) | (1 << PCINT18)
 
+#define TIMER_TOP_MS 20
+
 volatile uint8_t value = 0;
+volatile Boolean pressed = FALSE;
+volatile Boolean timer_0_init = FALSE;
+volatile Boolean timer_delay_enabled = FALSE;
+volatile uint16_t timer_delay = 0;
 
 void print_binary(int value) {
 	int mask_3 = 0b1000;
@@ -53,14 +59,58 @@ void decrement_led() {
 	print_binary(value);
 }
 
+void timer0_init_1_ms() {
+    TCCR0A |= (1 << WGM01);                   // CTC mode
+    OCR0A = 249;                              // Compare match every 1ms (F_CPU / Prescaler = 16,000,000 / 64 = 250,000 ticks/sec)
+    TIMSK0 |= (1 << OCIE0A);                  // Enable Compare Match A interrupt
+    TCCR0B |= (1 << CS01) | (1 << CS00);      // Prescaler 64
+    sei();                                    // Enable global interrupts
+	timer_0_init = TRUE;
+}
+
+void launch_delay_ms(void) {
+	if (!timer_0_init) {
+		timer0_init_1_ms();
+	}
+	CLEAR(PCICR, PCIE2);		// disable interupt PCINT2
+	CLEAR(PCMSK2, PCINT20);
+	CLEAR(PCMSK2, PCINT18);
+	timer_delay = 0;
+	timer_delay_enabled = TRUE;
+	SET(PCIFR, PCIF2);			// reset flag interrupt PCINT2
+}
+
+ISR(TIMER0_COMPA_vect) {
+	if (!timer_delay_enabled) {
+		return;
+	}
+	timer_delay++;
+	if (timer_delay >= TIMER_TOP_MS) {
+		// TOGGLE_ELEM(LED1);
+		timer_delay_enabled = FALSE;
+		SET(PCICR, PCIE2);		// re-enable interupt PCINT2
+		SET(PCMSK2, PCINT20);
+		SET(PCMSK2, PCINT18);
+	}
+}
+
 void on_press(int bit, void (*action)(void)) {
-	if ((TEST(PIND, bit)) == 0) {
+	// if ((TEST(PIND, bit)) == 0) {
+	//     action();
+	//     _delay_ms(20);
+	//     while ((TEST(PIND, bit)) == 0) {
+	//         continue;
+	//     }
+	//     _delay_ms(20);
+	// }
+	launch_delay_ms();
+	if (!pressed) {
+		// if ((TEST(PIND, bit)) == 0) {
+		// }
+		pressed = TRUE;
 	    action();
-	    _delay_ms(20);
-	    while ((TEST(PIND, bit)) == 0) {
-	        continue;
-	    }
-	    _delay_ms(20);
+	} else {
+		pressed = FALSE;
 	}
 }
 
@@ -84,6 +134,10 @@ int main() {
 }
 
 ISR(PCINT2_vect) {
-	on_press(SW1, increment_led);
-	on_press(SW2, decrement_led);
+	if (!TEST_PIN(BUTTON1)) {
+		on_press(SW1, increment_led);
+	}
+	if (!TEST_PIN(BUTTON2)) {
+		on_press(SW2, decrement_led);
+	}
 }