#define LED1 5
#define LED2 18
#define LED3 19

#define BTN1 21
#define BTN2 22
#define BTN3 23

int currentPick = 1;

void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);

  pinMode(BTN1, INPUT_PULLUP);
  pinMode(BTN2, INPUT_PULLUP);
  pinMode(BTN3, INPUT_PULLUP);

  Serial.begin(115200);
  startPick(currentPick);
}

void loop() {
  switch (currentPick) {
    case 1:
      if (digitalRead(BTN1) == LOW) {
        finishPick(1);
      }
      break;
    case 2:
      if (digitalRead(BTN2) == LOW) {
        finishPick(2);
      }
      break;
    case 3:
      if (digitalRead(BTN3) == LOW) {
        finishPick(3);
      }
      break;
    default:
      // All picks done
      break;
  }
}

void startPick(int pickNum) {
  Serial.print("Start Pick: ");
  Serial.println(pickNum);
  if (pickNum == 1) digitalWrite(LED1, HIGH);
  if (pickNum == 2) digitalWrite(LED2, HIGH);
  if (pickNum == 3) digitalWrite(LED3, HIGH);
}

void finishPick(int pickNum) {
  Serial.print("Picked Item: ");
  Serial.println(pickNum);
  if (pickNum == 1) digitalWrite(LED1, LOW);
  if (pickNum == 2) digitalWrite(LED2, LOW);
  if (pickNum == 3) digitalWrite(LED3, LOW);

  currentPick++;
  startPick(currentPick);
}