Simple flashing LEDs sketch for the Arduino UNO

The sketch below is a slightly modified version of the spaceship interface example. Pressing the button will cause the series of lights to blink rapidly.

// Create a global variable to hold the 
// state of the switch. This variable is persistent 
// throughout the program. Whenever you refer to 
// switchState, you’re talking about the number it holds
int switchstate = 0;

void setup(){
  // declare the LED pins as outputs 
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);

  // declare the switch pin as an input   
  pinMode(2, INPUT);
}

void loop(){
  // read the value of the switch
  // digitalRead() checks to see if there is voltage
  // on the pin or not  
  switchstate = digitalRead(2);

  // if the button is not pressed, turn on only the bottom LED
  if (switchstate == LOW) {
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
  }
  // if the button is pressed, flash all LEDs rapidly
  else {
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    delay(50);
    digitalWrite(3, LOW);
    digitalWrite(4, HIGH);
    digitalWrite(5, LOW);
    delay(50);  
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, HIGH);
    delay(50);
  }
}