BLINK Hat

int button = A4;
int first = 6;
int second = A8;
int third = A7;
int leds[] = {first, second, third};
int mode = 0;
bool buttonPressed = false;

void setup() {
  // put your setup code here, to run once:
  pinMode(first, OUTPUT);
  pinMode(second, OUTPUT);
  pinMode(third, OUTPUT);
  pinMode(button, INPUT_PULLUP);
}

bool checkButton(){
  if(!digitalRead(button)){
    buttonPressed = true;
  }
}

void modeOne(int speed){
  for(int i = 0; i < 255; i += 3){
    analogWrite(first, i);
    analogWrite(second, (i + 255/3) % 255);
    analogWrite(third, (i + 255/3) % 255);
    checkButton();
    delay(speed);
  }
  for(int i = 255; i >= 0; i -= 3){
    analogWrite(first, i);
    analogWrite(second, (i + 255/3) % 255);
    analogWrite(third, (i + 255/3) % 255);
    checkButton();
    delay(speed);
  }
}

void modeTwo(int speed){
  // modulus(%) is your friend
  //so the count (i) keeps going up. but using % makes it loop
  for(int i = 0; i < 3; i++){
    digitalWrite(leds[i % 3], HIGH);
    digitalWrite(leds[(i + 1) % 3], LOW);
    digitalWrite(leds[(i + 2) % 3], LOW);
    checkButton();
    delay(speed);
  }
  for(int i = 1; i >= 1; i--){
    digitalWrite(leds[i % 3], HIGH);
    digitalWrite(leds[(i + 1) % 3], LOW);
    digitalWrite(leds[(i + 2) % 3], LOW);
    checkButton();
    delay(speed);
  }
}

int numberOfModes = 2;

void loop() {
  switch(mode){
    case 0:
      modeOne(20);
      break;
    case 1:
      modeTwo(200);
      break;
  }
  
  if(buttonPressed){
    mode = (mode + 1) % numberOfModes;
    buttonPressed = false;
  }

}