const int buttonPin = 8;
const int led=7;

int path=1;
int a=1;
int previousState = HIGH;
unsigned int previousPress;
volatile int buttonFlag;
int buttonDebounce = 20;
 
 void setup()
 {
     pinMode(buttonPin, INPUT_PULLUP);
     pinMode(led,OUTPUT);

     }
     void loop()
     {
         if (path)
         {
analogWrite(led, 1000);
delay(1000);

         }
         else 
         {
          analogWrite(led , 0);
          delay(1000);
         }
         }
         
         void button_ISR()
         {
         buttonFlag = 1;
         if((millis() - previousPress) > buttonDebounce && buttonFlag)
         {
         previousPress = millis();
         if(digitalRead(buttonPin) == LOW && previousState == HIGH)
         {
         path =!path;
         previousState = LOW;
         }
          
          else if(digitalRead(buttonPin) == HIGH && previousState == LOW)
          {
          previousState = HIGH;
          }
          buttonFlag = 0;
          }
          }