Catch the beans: a tilt game on an 8x8 matrix, on an Arduino Uno

// Catch the beans: tip the board to slide a cup along the bottom of an 8x8
// matrix and catch the beans that fall from the top.
//
//   MAX7219 DIN -> pin 13    CLK -> pin 7    CS -> pin 8
//   MPU-6050 (GY-521) SDA -> A4    SCL -> A5
//   RGB LED red -> pin 6, green -> pin 9, blue -> pin 5, each through 220 ohm
//   passive buzzer -> pin 3
//
// The cup is three dots wide on the bottom row with walls one row up. A bean
// counts as caught when it drops into the middle of the cup. The RGB LED
// shows your lives: green, then yellow after one miss, red after two, and the
// third miss ends the game. Catch ten to win. Tip the board hard forward or
// back to start again.
//
// Drag the module's pitch to move the cup, and its roll to start a new game.

#include <Wire.h>
#include <LedControl.h>

const int MPU = 0x68;
const int LEAN = 5000;
const int RED_PIN = 6;
const int GREEN_PIN = 9;
const int BLUE_PIN = 5;
const int BUZZER = 3;
const int GOAL = 10;

LedControl lc = LedControl(13, 7, 8, 1);  // DIN, CLK, CS, modules

int cup = 3;       // the cup's middle column, 1 to 6
int beanX = 3;
int beanY = 0;
int caught = 0;
int missed = 0;
bool playing = true;
unsigned long lastFall = 0;
unsigned long lastMove = 0;

void readTilt(int &ax, int &ay) {
  Wire.beginTransmission(MPU);
  Wire.write(0x3B);
  Wire.endTransmission(false);
  Wire.requestFrom(MPU, 4);
  ax = Wire.read() << 8 | Wire.read();
  ay = Wire.read() << 8 | Wire.read();
}

void color(int r, int g, int b) {
  analogWrite(RED_PIN, r);
  analogWrite(GREEN_PIN, g);
  analogWrite(BLUE_PIN, b);
}

void showLives() {
  if (missed == 0) color(0, 160, 0);
  else if (missed == 1) color(160, 120, 0);
  else color(160, 0, 0);
}

void newBean() {
  beanX = random(1, 7);
  beanY = 0;
}

void draw() {
  lc.clearDisplay(0);
  lc.setLed(0, 7, cup - 1, true);
  lc.setLed(0, 7, cup, true);
  lc.setLed(0, 7, cup + 1, true);
  lc.setLed(0, 6, cup - 1, true);
  lc.setLed(0, 6, cup + 1, true);
  lc.setLed(0, beanY, beanX, true);
}

void picture(const byte rows[8]) {
  for (int row = 0; row < 8; row++) lc.setRow(0, row, rows[row]);
}

const byte SMILE[8] = {0x3C, 0x42, 0xA5, 0x81, 0xA5, 0x99, 0x42, 0x3C};
const byte CROSS[8] = {0x81, 0x42, 0x24, 0x18, 0x18, 0x24, 0x42, 0x81};

void newGame() {
  caught = 0;
  missed = 0;
  cup = 3;
  playing = true;
  showLives();
  newBean();
  Serial.println("new game");
}

void endGame(bool won) {
  playing = false;
  picture(won ? SMILE : CROSS);
  color(0, 0, 0);
  tone(BUZZER, won ? 1047 : 131, 600);
  Serial.println(won ? "you win" : "game over");
}

void land() {
  if (beanX == cup) {
    caught++;
    tone(BUZZER, 880, 120);
    Serial.print("caught ");
    Serial.println(caught);
    if (caught >= GOAL) {
      endGame(true);
      return;
    }
  } else {
    missed++;
    tone(BUZZER, 110, 300);
    Serial.print("missed ");
    Serial.println(missed);
    showLives();
    if (missed >= 3) {
      endGame(false);
      return;
    }
  }
  newBean();
}

void setup() {
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
  Serial.begin(9600);
  Wire.begin();
  Wire.beginTransmission(MPU);
  Wire.write(0x6B);  // wake the chip
  Wire.write(0);
  Wire.endTransmission();
  lc.shutdown(0, false);
  lc.setIntensity(0, 6);
  randomSeed(analogRead(A0));
  Serial.println("Mokxi Uno: catch the beans. Tip the board to move the cup.");
  newGame();
}

void loop() {
  int ax, ay;
  readTilt(ax, ay);
  if (!playing) {
    if (abs(ay) > 3 * LEAN) newGame();
    delay(50);
    return;
  }
  if (millis() - lastMove >= 150) {
    int was = cup;
    if (ax > LEAN && cup > 1) cup--;
    if (ax < -LEAN && cup < 6) cup++;
    if (cup != was) {
      lastMove = millis();
      Serial.print("cup at ");
      Serial.println(cup);
    }
  }
  if (millis() - lastFall >= 300) {
    lastFall = millis();
    beanY++;
    if (beanY >= 6) land();
  }
  if (playing) draw();
  delay(20);
}