diff --git a/README.md b/README.md
index 7dc0b68..03e253f 100644
--- a/README.md
+++ b/README.md
@@ -76,7 +76,7 @@ Hardware: FT232 USB-UART adapter connected to UPDI with a 4.7 kΩ resistor.
    ```
 4. Flash using pymcuprog:
    ```bash
-    pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 write -f build/main.hex
+    pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 erase && pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 write -f build/main.hex
    ```
 ## Hardware Setup (FT232 → ATtiny202 UPDI)
    ```bash
diff --git a/main.c b/main.c
index eacd981..44e9302 100644
--- a/main.c
+++ b/main.c
@@ -8,6 +8,10 @@
 #include <stdbool.h>
 #include <avr/io.h>
 #include <util/delay.h>
+#include <avr/sleep.h>
+#include <avr/interrupt.h>
+#include <avr/wdt.h>
+#include <avr/cpufunc.h> // for CCP
 
 #define BUTTON_PIN_MASK 0x01 // PA0 TODO: using RESET/UPDI pin
 #define PA1_SET_MASK 0x02    ///< LED 1–2
@@ -33,17 +37,54 @@ static inline void leds_off(void);
 static inline void leds_on(void);
 static void battery_level_indicator(void);
 static void handleSwitch(void);
+int main(void);
+
+void software_reset(void)
+{
+    CCP = CCP_IOREG_gc; // unlock protected registers
+    RSTCTRL.SWRR = 1;   // trigger software reset
+    cli();              // disable interrupts
+
+    // Unlock protected registers
+    CCP = CCP_IOREG_gc;
+
+
+    // Enable WDT with shortest period (~8 cycles)
+    WDT.CTRLA = WDT_PERIOD_8CLK_gc;
+
+    while (1)
+        ; // wait for reset
+}
+
+ISR(PORTA_PORT_vect)
+{
+    // Clear interrupt flags for PA0
+    PORTA.INTFLAGS = BUTTON_PIN_MASK;
+    if (!(VPORTA.IN & BUTTON_PIN_MASK)) // check PA0 low
+    {
+        // Turn off all LEDs
+        leds_off();
+        software_reset();
+    }
+}
 
 /**
  * @brief Main entry point
  */
 int main(void)
 {
+    bLedEnabled = true;
+    bBtnPressed = false;
+
+    cli(); // disable interrupts
+
+    //   register8_t backuop_dir = VPORTA.DIR;
     // Configure LED pins as outputs
     VPORTA.DIR = (PA1_SET_MASK | PA2_SET_MASK | PA3_SET_MASK | PA6_SET_MASK | PA7_SET_MASK);
 
     // Configure PA0 as input with pull-up
     VPORTA.DIR &= ~BUTTON_PIN_MASK;    // Input
+                                       //  register8_t backup_ctl = PORTA.PIN0CTRL;
     PORTA.PIN0CTRL = PORT_PULLUPEN_bm; // Pull-up enabled
 
     // Ensure all LEDs off at startup
@@ -79,6 +120,21 @@ int main(void)
             _delay_ms(BUTTON_IGNORE_DURATION_MS);
 
             blinkLed(true); // reset blink state machine
+            leds_off();
+
+            // TODO: activate the interrupt for PA0
+            PORTA.PIN0CTRL = PORT_PULLUPEN_bm | PORT_ISC_FALLING_gc;
+
+            sei(); // Enable global interrupts
+            while (1)
+            {
+                leds_off();
+                _delay_ms(BUTTON_IGNORE_DURATION_MS / 20);
+                leds_on();
+                _delay_ms(BUTTON_IGNORE_DURATION_MS / 20);
+            }
+
+            // TODO: add a isr that disabled all leds and loops in while(1);
         }
         else
         {