Dreidel spinner on an Arduino Uno

// Dreidel: press the button to spin, and the LCD whirls through the four
// letters, slowing down with a click for each one, until it lands. Then it
// says what the letter means and keeps score of the pot.
//
//   LCD       16x2 with an I2C backpack: SDA -> A4, SCL -> A5
//   button    pin 2 -> button -> GND        (INPUT_PULLUP): spin
//   piezo     pin 8 -> piezo -> GND
//
// The dreidel is a four-sided top played with at Hanukkah. Its sides carry
// the Hebrew letters nun, gimel, hei and shin (pe in Israel), for "a great
// miracle happened there". In the game everyone puts a token in the pot, and
// each spin says what to do:
//
//   nun     nothing happens
//   gimel   take the whole pot
//   hei     take half the pot
//   shin    put one token in
//
// The LCD's font has no Hebrew letters, so the screen spells the names. The
// spin slows the way a real top does: the wait between letters grows a little
// each time, and the letter it stops on is picked at random before the spin
// starts, each one equally likely.
//
// Things to try. Press the button to spin. Start the pot bigger with POT.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

const int BUTTON_PIN = 2;
const int PIEZO_PIN = 8;
const int POT = 10;

LiquidCrystal_I2C lcd(0x27, 16, 2);

const char *LETTERS[4] = {"Nun", "Gimel", "Hei", "Shin"};
const char *RULES[4] = {"Nothing happens", "Take the pot!", "Take half", "Put one in"};

int pot = POT;
int spins = 0;

void face(int i) {
  lcd.setCursor(0, 0);
  lcd.print("   ");
  lcd.print(LETTERS[i]);
  lcd.print("        ");
}

void setup() {
  Serial.begin(9600);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  lcd.init();
  lcd.backlight();
  randomSeed(analogRead(A0));
  lcd.print("Dreidel! Pot ");
  lcd.print(pot);
  lcd.setCursor(0, 1);
  lcd.print("Press to spin");
  Serial.println("Happy Hanukkah! Press the button to spin the dreidel");
}

void loop() {
  if (digitalRead(BUTTON_PIN) == HIGH) return;
  while (digitalRead(BUTTON_PIN) == LOW) delay(10);

  spins++;
  int land = random(0, 4);
  int turns = 16 + random(0, 4) * 4 + land;   // whole turns, then the letter
  lcd.clear();
  Serial.print("Spin ");
  Serial.print(spins);
  Serial.println("...");
  unsigned long wait = 30;
  for (int t = 0; t <= turns; t++) {
    face(t % 4);
    tone(PIEZO_PIN, 900, 8);
    delay(wait);
    wait = wait * 17 / 16 + 2;   // slowing down
  }

  // What the letter does to the pot. If it empties, both players put one in.
  if (land == 1) pot = 0;
  else if (land == 2) pot -= (pot + 1) / 2;
  else if (land == 3) pot++;
  if (pot == 0) pot = 2;

  lcd.setCursor(0, 1);
  lcd.print(RULES[land]);
  Serial.print(LETTERS[land]);
  Serial.print(": ");
  Serial.print(RULES[land]);
  Serial.print(" The pot has ");
  Serial.println(pot);
  tone(PIEZO_PIN, land == 1 ? 1320 : 660, 200);
}