LED matrix + Joystick snake game

snake.ino

#include <LedControl.h>

// Display
int din = 8;
int clk = 10;
int cs = 9;

// Joystick click
int sw = 5;

// Joystick move
int x = 3;
int y = 4;

int tilt_max = 700;
int tilt_min = 300;

LedControl matrix(din, clk, cs);

int food_x;
int food_y;

int head_last_x;
int head_last_y;

int width = 8;

boolean needNewFood = true;

int max_body_length = 20; // WTF?
int head = 0;
int tail = 0;
int body_xs[20];
int body_ys[20];

boolean gameOver = false;

void setup() {
  Serial.begin(9600);
  randomSeed(analogRead(0));

  start();
}

void loop() {
  if (!gameOver) {
    head_last_x = body_xs[head];
    head_last_y = body_ys[head];

    moveJoystick();

    // Move head
    ledOn(body_xs[head], body_ys[head]);

    delay(100);

    // Generate new food
    if (needNewFood) {
      newFood();
    }

    if (headAndFoodCollide()) {
      Serial.println("Om-nom-nom");
      growSnake();
      needNewFood = true;
    }

    if(headCollidesWithBody()) {
      Serial.println("Collision!");
      gameOver = true;
    }
  }
  else {
    for (int i = 0; i < width; i++) {
      matrix.setRow(0, i, B11111111);
      delay(500);
    }
    // matrix.shutdown(0, false);

    if(digitalRead(sw) == 0) {
      Serial.println("Reset");
      gameOver = false; 
      for (int i = 0; i < width; i++) {
        matrix.setRow(0, i, B00000000);
        delay(500);
      }
      start();
    }
  }
}

void start() {
  matrix.shutdown(0, false);
  matrix.setIntensity(0, 2); // 0-16

  head = 0;
  tail = 0;
  food_x = 0;
  food_y = 0;
  head_last_x = 0;
  head_last_y = 0;
  needNewFood = true;

  randomStart();
}

void moveJoystick() {
  // Movements
  if (body_xs[head] < 7 && analogRead(x) > tilt_max) {
    moveSnake();
    body_xs[head]++;
  }
  else if (body_xs[head] > 0 && analogRead(x) < tilt_min) {
    moveSnake();
    body_xs[head]--;
  }
  else if (body_ys[head] < 7 && analogRead(y) < tilt_min) {
    moveSnake();
    body_ys[head]++;
  }
  else if (body_ys[head] > 0 && analogRead(y) > tilt_max) {
    moveSnake();
    body_ys[head]--;
  }
}

void newFood() {
  do {
    food_x = random(width);
    food_y = random(width);
  }
  while (bodyAndFoodCollide());

  Serial.print("New food at (");
  Serial.print(food_x + 1);
  Serial.print(", ");
  Serial.print(food_y + 1);
  Serial.print(")");
  Serial.println();

  needNewFood = false;
  ledOn(food_x, food_y);
}

boolean headAndFoodCollide() {
  if(food_x == body_xs[head] && food_y == body_ys[head]) {
    // Reset values to prevent multiple loop events
    food_x = -1;
    food_y = -1;
    return true;
  }
  return false;
}

boolean bodyAndFoodCollide() {
  for (int i = 0; i <= tail; i++) {
    if(food_x == body_xs[i] && food_y == body_ys[i]) {
      // Reset values to prevent multiple loop events
      food_x = -1;
      food_y = -1;
      return true;
    }
    return false;
  }
}

boolean headCollidesWithBody() {
  for (int i = 1; i <= tail; i++) {
    if (body_xs[head] == body_xs[i] && body_ys[head] == body_ys[i]) {
      return true;
    }
  }
  return false;
}

void moveSnake() {
  ledOff(body_xs[tail], body_ys[tail]);
  shiftArray();
}

void growSnake() {
  tail++;
  shiftArray();
  body_xs[1] = head_last_x;
  body_ys[1] = head_last_y;
}

void shiftArray() {
  for (int i = tail; i > 0; i--) {
    body_xs[i] = body_xs[i - 1];
    body_ys[i] = body_ys[i - 1];
  }
}

void printSnake() {
  Serial.println("Snake:");
  for (int i = 0; i <= tail; i++) {
    Serial.print("(");
    Serial.print(body_xs[i] + 1);
    Serial.print(", ");
    Serial.print(body_ys[i] + 1);
    Serial.println(")");
  }
}

void ledOn(int x, int y) {
  matrix.setLed(0, x, y, true);
}

void ledOff(int x, int y) {
  matrix.setLed(0, x, y, false);
}

void ledOnDebug(int x, int y) {
  Serial.print("Led ");
  Serial.print("(");
  Serial.print(x + 1);
  Serial.print(", ");
  Serial.print(y + 1);
  Serial.print(")");
  Serial.println(" set ON");
  matrix.setLed(0, x, y, true);
}

void ledOffDebug(int x, int y) {
  Serial.print("Led ");
  Serial.print("(");
  Serial.print(x + 1);
  Serial.print(", ");
  Serial.print(y + 1);
  Serial.print(")");
  Serial.println(" set OFF");
  matrix.setLed(0, x, y, false);
}

void randomStart() {
  // Start from a random cell
  body_xs[head] = random(width);
  body_ys[head] = random(width);
  ledOn(body_xs[head], body_ys[head]);
  Serial.print("Starting at (");
  Serial.print(body_xs[head] + 1);
  Serial.print(", ");
  Serial.print(body_ys[head] + 1);
  Serial.print(")");
  Serial.println();
}