var canvas = document.getElementById("the-game");
var context = canvas.getContext("2d");
var game, snake, food;
game = {
score: 0,
fps: 8,
over: false,
message: null,
start: function() {
game.over = false;
game.message = null;
game.score = 0;
game.fps = 8;
snake.init();
food.set();
},
stop: function() {
game.over = true;
game.message = 'GAME OVER - PRESS SPACEBAR';
},
drawBox: function(x, y, size, color) {
context.fillStyle = color;
context.beginPath();
context.moveTo(x - (size / 2), y - (size / 2));
context.lineTo(x + (size / 2), y - (size / 2));
context.lineTo(x + (size / 2), y + (size / 2));
context.lineTo(x - (size / 2), y + (size / 2));
context.closePath();
context.fill();
},
drawScore: function() {
context.fillStyle = '#999';
context.font = (canvas.height) + 'px Impact, sans-serif';
context.textAlign = 'center';
context.fillText(game.score, canvas.width / 2, canvas.height * 0.9);
},
drawMessage: function() {
if (game.message !== null) {
context.fillStyle = '#00F';
context.strokeStyle = '#FFF';
context.font = (canvas.height / 10) + 'px Impact';
context.textAlign = 'center';
context.fillText(game.message, canvas.width / 2, canvas.height / 2);
context.strokeText(game.message, canvas.width / 2, canvas.height / 2);
}
},
resetCanvas: function() {
context.clearRect(0, 0, canvas.width, canvas.height);
}
};
snake = {
size: canvas.width / 40,
x: null,
y: null,
color: '#0F0',
direction: 'left',
sections: [],
init: function() {
snake.sections = [];
snake.direction = 'left';
snake.x = canvas.width / 2 + snake.size / 2;
snake.y = canvas.height / 2 + snake.size / 2;
for (var i = snake.x + (5 * snake.size); i >= snake.x; i -= snake.size) {
snake.sections.push(i + ',' + snake.y);
}
},
move: function() {
switch (snake.direction) {
case 'up':
snake.y -= snake.size;
break;
case 'down':
snake.y += snake.size;
break;
case 'left':
snake.x -= snake.size;
break;
case 'right':
snake.x += snake.size;
break;
}
snake.checkCollision();
snake.checkGrowth();
snake.sections.push(snake.x + ',' + snake.y);
},
draw: function() {
for (var i = 0; i < snake.sections.length; i++) {
snake.drawSection(snake.sections[i].split(','));
}
},
drawSection: function(section) {
game.drawBox(parseInt(section[0]), parseInt(section[1]), snake.size, snake.color);
},
checkCollision: function() {
if (snake.isCollision(snake.x, snake.y) === true) {
game.stop();
}
},
isCollision: function(x, y) {
if (x < snake.size / 2 ||
x > canvas.width ||
y < snake.size / 2 ||
y > canvas.height ||
snake.sections.indexOf(x + ',' + y) >= 0) {
return true;
}
},
checkGrowth: function() {
if (snake.x == food.x && snake.y == food.y) {
game.score++;
if (game.score % 5 == 0 && game.fps < 60) {
game.fps++;
}
food.set();
} else {
snake.sections.shift();
}
}
};
food = {
size: null,
x: null,
y: null,
color: '#0FF',
set: function() {
food.size = snake.size;
food.x = (Math.ceil(Math.random() * 10) * snake.size * 4) - snake.size / 2;
food.y = (Math.ceil(Math.random() * 10) * snake.size * 3) - snake.size / 2;
},
draw: function() {
game.drawBox(food.x, food.y, food.size, food.color);
}
};
var inverseDirection = {
'up': 'down',
'left': 'right',
'right': 'left',
'down': 'up'
};
var keys = {
up: [38, 75, 87],
down: [40, 74, 83],
left: [37, 65, 72],
right: [39, 68, 76],
start_game: [13, 32]
};
function getKey(value){
for (var key in keys){
if (keys[key] instanceof Array && keys[key].indexOf(value) >= 0){
return key;
}
}
return null;
}
addEventListener("keydown", function (e) {
var lastKey = getKey(e.keyCode);
if (['up', 'down', 'left', 'right'].indexOf(lastKey) >= 0
&& lastKey != inverseDirection[snake.direction]) {
snake.direction = lastKey;
} else if (['start_game'].indexOf(lastKey) >= 0 && game.over) {
game.start();
}
}, false);
var requestAnimationFrame = window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame;
function loop() {
if (game.over == false) {
game.resetCanvas();
game.drawScore();
snake.move();
food.draw();
snake.draw();
game.drawMessage();
}
setTimeout(function() {
requestAnimationFrame(loop);
}, 1000 / game.fps);
}
requestAnimationFrame(loop);
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