#define sw 32
#define led 4
int now, old;
int status = 0;

void setup() {
  pinMode(sw, INPUT_PULLUP);
  pinMode(led, OUTPUT);
}

void loop() {
  int old = now;
  now = digitalRead(sw);
  if ((old != now)&&(now == 0)){
    status = !status;
  }
  digitalWrite(led, status);
}