scratch.c

int val;
int scratch_min = 12;
int scratch_max = 128;
int scratches = 0;
boolean scratched = false;

void setup() {
  Serial.begin(9600);
}

void loop() {
  val = analogRead(A0);
  if (millis() % 100 > 90) {
    if (scratches > 2) {
      scratched = true;
      Serial.println("scratched");
    } else {
      scratched = false;
      Serial.println("not scratched");
    }
    scratches -= 1;
  } else {
    if (scratches < 5 && val >= scratch_min && val <= scratch_max) {
      scratches++;
    }
  }
  delay(10);
}