void setup() {
pinMode(12, OUTPUT);
pinMode(7, INPUT_PULLUP);

}
bool led12 = HIGH;

void loop() {
 
if ( digitalRead(7)==0){
   if(millis()%500==0){
  led12=!led12;
  digitalWrite(12,led12);
   }

delay(1);
}
else{
  digitalWrite(12, LOW);
}
}