let rows = 15;

let gridSize = 21;

let winWidth = cols * gridSize;

let winHeight = rows * gridSize;

let food = { x: 0, y: 0 };

let snake = {

  x: 0,

  y: 0,

  xSpeed: 0,

  ySpeed: 0,

  body: [],

};

let score = 0;

let gamePaused = false;

let gameOver = false;

let gameStarted = false;

let fps = 5;

​

​

​

​

// ====================

//        Food

// ====================

​

// Draw the food as

// a red square.

function drawFood() {

  let x = food.x * gridSize;

  let y = food.y * gridSize;

  fill(255, 255, 0);

  square(x, y, gridSize);

}

​

// Move the food to a

// random location.

function moveFood() {

  food.x = floor(random(cols));

  food.y = floor(random(rows));

}

​

// ====================

//        Snake

// ====================

​

// Reset the snake's data.

function resetSnake() {

  // Start at the center.

  snake.x = floor(cols / 2);

  snake.y = floor(rows / 2);

  // Move to the right.

  snake.xSpeed = 1;

  snake.ySpeed = 0;

  // Add an array to manage

  // the body.

  snake.body = [];

  // Create a head segment.

  let head = {

    x: snake.x,

    y: snake.y,

  };

  // Add the head to the body.

  snake.body.push(head);

}

​

// End the game when the

// snake collides an edge.

function checkEdges() {

  // Right edge.

  if (snake.x === cols) {

    gameOver = true;

    return;

  }

  // Left edge.

  if (snake.x === -1) {

    gameOver = true;

    return;

  }

  // Top edge.

  if (snake.y === -1) {

    gameOver = true;

    return;

  }

  // Bottom edge.

  if (snake.y === rows) {

    gameOver = true;

    return;

  }

}

​

​

// Move the snake forward.

function moveSnake() {

  snake.x = snake.x + snake.xSpeed;

  snake.y = snake.y + snake.ySpeed;

}

​

// Update the positions of the

// snake's body segments.

function updateBody() {

  // Update the end of the tail.

  for (let i = snake.body.length - 1; i > 0; i -= 1) {

    snake.body[i].x = snake.body[i - 1].x;

    snake.body[i].y = snake.body[i - 1].y;

  }

  // Update the head.

  snake.body[0].x = snake.x;

  snake.body[0].y = snake.y;

}

​

// Draw the snake.

function drawSnake() {

  fill(0, 255, 0);

  for (let segment of snake.body) {

    let x = segment.x * gridSize;

    let y = segment.y * gridSize;

    square(x, y, gridSize);

  }

}

​

// Update the snake's movement.

function changeDir(xSpeed, ySpeed) {

  snake.xSpeed = xSpeed;

  snake.ySpeed = ySpeed;

}

​

// Manage the snake's diet.

function checkFood() {

  if (snake.x === food.x && snake.y === food.y) {

    // Add a new body segment.

    let segment = { x: -1, y: -1 };

    snake.body.push(segment);

    // Update the score.

    score += 10;

    // Place the food in a

    // random location.

    moveFood();

  }

}

​

// End the game if the snake

// collides with its tail.

function checkSelf() {

  for (let i = 1; i < snake.body.length; i += 1) {

    let segment = snake.body[i];

    if (snake.x === segment.x && snake.y === segment.y) {

      gameOver = true;

      return;

    }

  }

}

​

// ====================

//      Controls

// ====================

​

// Directions: up, down, left, right.

​

function goUp() {

  snake.xSpeed = 0;

  snake.ySpeed = -1;

}

​

function goDown() {

  snake.xSpeed = 0;

  snake.ySpeed = 1;

}

​

function goLeft() {

  snake.xSpeed = -1;

  snake.ySpeed = 0;

}

​

function goRight() {

  snake.xSpeed = 1;

  snake.ySpeed = 0;

}

​

// Use arrow keys to control

// the snakes' motion.

function keyPressed() {

  if (keyCode === UP_ARROW) {

    goUp();

  }

  if (keyCode === DOWN_ARROW) {

    goDown();

  }

  if (keyCode === LEFT_ARROW) {

    goLeft();

  }

  if (keyCode === RIGHT_ARROW) {

    goRight();

  }

}

​

// Start the game.

function startGame() {

  score = 0;

  gameStarted = true;

  gamePaused = false;

  if (gameOver === true) {

    resetSnake();

    gameOver = false;

  }

  loop();

}

​

// Pause the game.

function pauseGame() {

  gamePaused = true;

}

​

// ====================

//       Messages

// ====================

​

// Start message.

function displayStartMessage() {

  textSize(20);

  textAlign(CENTER);

  fill(255, 0, 0);

  // textFont(myFont);

  textFont('Courier New');

  text('Press ▶ to Start', width / 2, height / 2);

}

​

// End message.

function displayEndMessage() {

  background(0);

  textSize(40);

  textAlign(CENTER);

  fill(255, 0, 0);

  // textFont(myFont);

  textFont('Courier New');

  text('Game Over', width / 2, height / 2);

  textSize(14);

  text('Press ▶ to Start', width / 2, height / 2 + 50);

}

​