184 lines of code Snake game written in 5mbg.com

gistfile1.txt

// general defs
const LEVEL_WIDTH = 40;						// playable region width
const LEVEL_HEIGHT = 20;					// playable region height
const SCALE = 4;							// scale factor for rendering
const SCREEN_WIDTH = LEVEL_WIDTH * SCALE;   // screen width
const SCREEN_HEIGHT = LEVEL_HEIGHT * SCALE; // screen height

// set engine init flags
initFlags.gfx.crispRendering = true;			// make rendering pixelated / crisp
initFlags.gfx.fixedResolutionX = SCREEN_WIDTH;	// lock x resolution
initFlags.gfx.fullscreen = false;				// play in windowed mode
initFlags.gfx.defaultViewportSize = {x:SCREEN_WIDTH, y:SCREEN_HEIGHT};	// set default viewport size

// set fixed update to slow rate of 4 per second. we put all our logic in the fixed updates
initFlags.game.fixedUpdatesPerSecond = 10;

// game states
var timeForStep = 0; 	// time until we perform next update
var snake = [];			// snake body (head is index 0)
var food;				// the food that currently appears in level
var direction;			// current direction
var lastDirection;		// last direction we moved to, to prevent going opposite direction
var isDead = false;		// did we lose?
var gameOverText;		// game over text

// generate random position
function generateRandomPos()
{
  var x = 1 + Math.floor(Math.random() * (LEVEL_WIDTH - 2));
  var y = 1 + Math.floor(Math.random() * (LEVEL_HEIGHT - 2));
  return gfx.Point(x, y);
}

// get snake's head
function head() 
{
  return snake[0];
}

// create new food at a random position
function createFood()
{
  food = generateRandomPos();
  logger.info("New food at: " + food.x + ", " + food.y);
}

// start a new game
function newGame() 
{
  // cancel death state
  isDead = false;
  
  // reset snake and reiction
  snake = [gfx.Point(1, 1)];
  lastDirection = direction = 'right';
  
  // place starting food
  createFood();
}

// init game
onInit(() =>
{
  // init game over text
  gameOverText = gfx.TextSprite("Game Over\nSpace = Restart", 
                                gfx.Point(SCREEN_WIDTH / 2, 30),
                                {fontSize: 18, alignment: gfx.TextAlignment.Center});
  
  // create new game
  newGame();
});

// do per-frame updates
// we only get input from user here
onUpdate(() =>
{ 
  // handle death screen
  if (isDead && input.down('space')) {
    newGame();
  }
  
  // change direction (input always works, not just during steps)
  if (input.down('left_arrow') || input.down('a')) {
  	if (lastDirection !== 'right') direction = 'left';
  }
  if (input.down('right_arrow') || input.down('d')) {
  	if (lastDirection !== 'left') direction = 'right';
  }
  if (input.down('up_arrow') || input.down('w')) {
  	if (lastDirection !== 'down') direction = 'up';
  }
  if (input.down('down_arrow') || input.down('s')) {
  	if (lastDirection !== 'up') direction = 'down';
  }
});
  
// do fixed updates - here we actually do logic
onFixedUpdate(() =>
{ 
  // skip updates on death
  if (isDead) {
    return;
  }
  // are we growing this frame?
  var growNow = false;

  // are we eating the food?
  if (food.equals(head()))
  {
    createFood();
  	growNow = true;
  }
  
  // move snake body
  var prevTail = snake[snake.length-1].clone();
  for (var i = snake.length-1; i > 0; --i) {
    snake[i] = snake[i-1].clone();
  }
  
  // get head part
  var snakehead = head();
    
  // move snake head
  var prevHead = head().clone();
  switch (direction) {
    case "left":
      snakehead.x--;
      break;
	case "right":
      snakehead.x++;
      break;
	case "up":
      snakehead.y--;
      break;
	case "down":
      snakehead.y++;
      break;
  }
  lastDirection = direction;
  
  // do growing
  if (growNow) {
    snake.push(prevTail);
  }
  
  // check death condition by level border
  if ((snakehead.x <= 0) || (snakehead.y <= 0) || (snakehead.x >= LEVEL_WIDTH-1) || (snakehead.y >= LEVEL_HEIGHT-1)) {
	isDead = true;
  }
  // check death condition by stepping on self
  for (var i = 1; i < snake.length; ++i) {
    if (snakehead.equals(snake[i])) {
		isDead = true;
    }
  }
});
    
// draw game
onDraw(() =>
{
  // clear screen
  gfx.clear(isDead ? gfx.Color.darkred : gfx.Color.black);
  
  // draw snake head and body
  gfx.drawPixel(head(), gfx.Color.lime, SCALE);
  for (var i = 1; i < snake.length; ++i) {
    gfx.drawPixel(snake[i], i % 2 == 0 ? gfx.Color.green : gfx.Color.darkgreen, SCALE);
  }
  
  // draw food
  gfx.drawPixel(food, gfx.Color.blue, SCALE);
  
  // draw level borders
  gfx.drawRectangle(gfx.Rectangle(0,0,LEVEL_WIDTH*SCALE,SCALE), gfx.Color.red);
  gfx.drawRectangle(gfx.Rectangle(0,(LEVEL_HEIGHT-1)*SCALE,LEVEL_WIDTH*SCALE,SCALE), gfx.Color.red);
  gfx.drawRectangle(gfx.Rectangle(0,0,SCALE,LEVEL_HEIGHT*SCALE), gfx.Color.red);
  gfx.drawRectangle(gfx.Rectangle((LEVEL_WIDTH-1)*SCALE,0,SCALE,LEVEL_HEIGHT*SCALE), gfx.Color.red);
  
  // draw death state
  if (isDead) {
  	gfx.drawPixel(head(), gfx.Color.red, SCALE);
    gfx.drawText(gameOverText);
  }
});

Live demo:

http://5mbg.com/play/snake/