const int PIR_PIN = 8;
const int BUZ_PIN = 7;
const int LED_PIN = 6;
const int BTN_PIN = 2;
int state;
void setup() {
 Serial.begin(115200);
 pinMode(BTN_PIN, INPUT_PULLUP);
 pinMode(PIR_PIN, INPUT_PULLUP);
 pinMode(BUZ_PIN, OUTPUT);
 pinMode(LED_PIN, OUTPUT);
 state = 0;
}
void loop() {
if (state == 0) {
 // ceck the PIR sensor
 if (digitalRead(PIR_PIN)) {// trun everything on
 tone(BUZ_PIN, 440);
 digitalWrite(LED_PIN, HIGH);
 Serial.print("Motion detected!\t");
 Serial.println("Alarm On");
 state = 0;
 }
}
else { // here state must be 1...
 // check the buttom
 if (digitalRead(BTN_PIN) ) { //turn everything off
 noTone(BUZ_PIN);
 digitalWrite(LED_PIN, LOW);
 Serial.print("Alarm canceled \t");
 Serial.println("Alarm Off\n");
 state = 0;
 }
}
}