Adding a Button to the 3 LEDs and Photoresistor

/*
 *  Jung Min Yean
 *  04/04/19
 *  Learning How to Use a Photoresistor with LEDs
 */

 const int LedPin1 = 9;
 const int LedPin2 = 10;
 const int LedPin3 = 11;
 const int PhotoPin = A0;
 int PhotoVal = 0;
 unsigned long timeStart = 0;
 int Max = 0;
 int Min = 1000;
 boolean currentVal;
 boolean lastVal;
 const int Button = 2;

void setup()
{
 pinMode(LedPin1, OUTPUT);
 pinMode(LedPin2, OUTPUT);
 pinMode(LedPin3, OUTPUT);
 pinMode(PhotoPin, INPUT);
 pinMode(Button, INPUT);
 Serial.begin(9600);
 digitalWrite(LedPin1, HIGH);
 delay(100);
 digitalWrite(LedPin1,LOW);
  calibrate();
}
boolean debounce(boolean last)
{
  boolean current = digitalRead(Button);
  if (last != current)
  {
    delay(5);
    current = digitalRead(Button);
    Serial.println(current);
  }
  return current;
}

void calibrate()
 {
  Max = 0;
  Min = 1000;
  analogWrite(LedPin1,200);
  analogWrite(LedPin2, 0);
  analogWrite(LedPin3,0);
  delay(200);
  analogWrite(LedPin1, 0);
  analogWrite(LedPin2, 0);
  analogWrite(LedPin3,0);
  timeStart = millis();
  while (millis()-timeStart <= 5000)
  {
    delay(5);
    PhotoVal = analogRead(PhotoPin);
    Serial.println(PhotoVal);
    if(PhotoVal > Max)
    {
      Max = PhotoVal;
    }
    if(PhotoVal < Min)
    {
      Min = PhotoVal;
    }
  }
  Serial.print("The Max Value is ");
  Serial.println(Max);
  Serial.print("The Min Value is");
  Serial.println(Min);
 }

void loop()
{
 currentVal = debounce(lastVal);
 if (lastVal == LOW && currentVal == HIGH)    // Checks if the button has been pressed
 {
  calibrate();
 }
  PhotoVal = analogRead(PhotoPin);
  // Serial.println(PhotoVal);
  // Serial.print("      ");
  int MapVal = map(PhotoVal,Min,Max,255,0);
  MapVal = constrain(MapVal, 0,255);
  // Serial.println(MapVal);
  analogWrite(LedPin1, MapVal);
  analogWrite(LedPin2, MapVal);
  analogWrite(LedPin3, MapVal);
  lastVal=currentVal;
}