Ofrenda candles on an Arduino Uno

// Ofrenda candles: six candle lights for an ofrenda, the home altar of Día de
// los Muertos. Press the button to light one candle at a time, one for each
// person you are remembering, and each one flickers like a real flame.
//
//   candles   pins 3, 5, 6, 9, 10, 11 -> 220 ohms -> yellow LED -> GND, six
//   button    pin 2 -> button -> GND        (INPUT_PULLUP)
//
// On Día de los Muertos, on November 1st and 2nd, families in Mexico and
// around the world welcome back the spirits of loved ones who have died. The
// ofrenda holds their photos, their favorite foods, marigolds, sugar skulls
// and candles, often one for each person, to light their way home.
//
// Every candle has its own PWM pin, the six an Uno has, so each can flicker
// on its own: every few milliseconds it picks a brightness near the top,
// with an occasional deeper dip, so no two candles move together. LEDs are a
// good choice for an ofrenda full of paper decorations and dry flowers.
//
// Press the button once more after the sixth and they all fade out together.
//
// Things to try. Press the button six times. Make the flames calmer by
// raising the lowest brightness in flicker().

const int CANDLES = 6;
const int PINS[CANDLES] = {3, 5, 6, 9, 10, 11};
const int BUTTON_PIN = 2;

int lit = 0;

void flicker() {
  for (int i = 0; i < CANDLES; i++) {
    if (i < lit) {
      int v = random(0, 12) == 0 ? random(60, 140) : random(170, 256);
      analogWrite(PINS[i], v);
    } else {
      analogWrite(PINS[i], 0);
    }
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  for (int i = 0; i < CANDLES; i++) pinMode(PINS[i], OUTPUT);
  Serial.println("Ofrenda ready: press the button to light a candle");
}

void loop() {
  if (digitalRead(BUTTON_PIN) == LOW) {
    if (lit < CANDLES) {
      lit++;
      Serial.print("Candle ");
      Serial.print(lit);
      Serial.println(" lit");
    } else {
      for (int v = 200; v >= 0; v -= 5) {
        for (int i = 0; i < CANDLES; i++) analogWrite(PINS[i], v);
        delay(20);
      }
      lit = 0;
      Serial.println("All candles out");
    }
    while (digitalRead(BUTTON_PIN) == LOW) flicker();
    delay(50);
  }
  flicker();
  delay(random(40, 90));
}