int led = 12;
int btn =10;
bool ledstate = 0;
bool btnstate = false;

void setup(){
Serial.begin(115200);
pinMode(btn, INPUT_PULLUP);
pinMode(led, OUTPUT);

}

void loop(){
  btnstate = digitalRead(btn);
if(btnstate == LOW && !ledstate){
ledstate = true;
digitalWrite(led, HIGH);
delay(250);
}else if(btnstate == LOW && ledstate){
  ledstate == false;
  digitalWrite(led, LOW);
  delay(250);
}

}