gistfile1.dart

import 'dart:html';
import 'dart:math';
import 'dart:async';

var ctx;
List<Point> snake = [new Point(12, 10)];
Point direction = new Point(1, 0);
Point food;

void main() {
  CanvasElement canvas = querySelector("#game");
  ctx = canvas.context2D;
  ctx.fillStyle = "black";
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  food = getNewFood();
  drawBlock(food);

  new Timer.periodic(const Duration(milliseconds: 100), init);
  
  document.addEventListener("keydown", (e) {
    switch (e.keyCode) {
      case 39: direction = new Point(1, 0); break; // right
      case 40: direction = new Point(0, 1); break; // down
      case 37: direction = new Point(-1, 0); break; // left
      case 38: direction = new Point(0, -1); break; // up
    }
  });
}

class Point {
  int x;
  int y;
  Point(int x, int y) {
    this.x = x;
    this.y = y;
  }

  int get hashCode {
    int result = 17;
    result = 37 * result + x.hashCode;
    result = 37 * result + y.hashCode;
    return result;
  }

  bool operator==(other) {
    if (other is! Point) return false;
    Point point = other;
    return (point.x == x && point.y == y);
  }
}

void drawBlock(Point pos) {
  ctx.strokeStyle = "rgba(255,255,255, 0.5)";
  ctx.strokeRect(pos.x * 10 + 0.5, pos.y * 10 + 0.5, 8, 8);
  ctx.fillStyle = "rgba(255,255,255, 0.2)";
  ctx.fillRect(pos.x * 10 + 0.5, pos.y * 10 + 0.5, 8, 8);
}

void eraseBlock(Point pos) {
  ctx.fillStyle = "black";
  ctx.fillRect(pos.x * 10, pos.y * 10, 10, 10);
}

int randomCoord() => new Random().nextInt(30);

Point getNewFood() {
  return new Point(randomCoord(), randomCoord());
}

bool isCollision(Point newHead) {
  return snake.contains(newHead) || newHead.x < 0 || newHead.x > 30 || newHead.y < 0 || newHead.y > 30;
}

bool gameOver() => false;

bool game() {

  var head = snake.first;
  var newHead = new Point(head.x + direction.x, head.y + direction.y);

  if (isCollision(newHead)) {
    return gameOver();
  }
  
  else if (newHead == food) {
    food = getNewFood();
    snake = new List<Point>()
      ..add(newHead)
      ..addAll(snake);
    drawBlock(newHead);
    drawBlock(food);
  }
  
  else {
    eraseBlock(snake.last);
    snake = new List<Point>()
      ..add(newHead)
      ..addAll(snake.sublist(0, snake.length - 1));
    drawBlock(newHead);
  }

  return true;
}

void init(timer) {
  if (!game()) {
    timer.cancel();
  }
}