// variables

int GREEN = 27;

int YELLOW = 26;

int RED = 25;

int DELAY_GREEN = 1000;

int DELAY_YELLOW = 500;

int DELAY_RED = 2000;

// basic functions

void setup()

{

  pinMode(GREEN, OUTPUT);

  pinMode(YELLOW, OUTPUT);

  pinMode(RED, OUTPUT);

}

void loop()

{

  green_light();

  delay(DELAY_GREEN);

  yellow_light();

  delay(DELAY_YELLOW);

  red_light();

  delay(DELAY_RED);

}

void green_light()

{

  digitalWrite(GREEN, HIGH);

  digitalWrite(YELLOW, LOW);

  digitalWrite(RED, LOW);

}

void yellow_light()

{

  digitalWrite(GREEN, LOW);

  digitalWrite(YELLOW, HIGH);

  digitalWrite(RED, LOW);

}

void red_light()

{

  digitalWrite(GREEN, LOW);

  digitalWrite(YELLOW, LOW);

  digitalWrite(RED, HIGH);

}