Arduino worksheet 2, question 3

arduino ws2 #3

void setup()
{
    pinMode(12, OUTPUT);
    pinMode(2, INPUT_PULLUP);
    pinMode(4, INPUT_PULLUP);
}

int led = LOW;
int button_right;
int last_button_right;
int button_left;
int last_button_left;

void loop()
{
    last_button_right = button_right;
    button_right = digitalRead(2);
    if (button_right == LOW && last_button_right == HIGH)
    {
        led = LOW;
    }

    last_button_left = button_left;
    button_left = digitalRead(4);
    if (button_left == LOW && last_button_left == HIGH)
    {
        led = HIGH;
    }

    digitalWrite(12, led);
}