Preview
Source Code
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<!-- This script got from www.devanswer.com -->
<style>
.center{text-align:center}
#space-invaders {
margin: 0 auto;
display: block;
background: white
}
</style>
</head>
<body>
<p class="center">Space Invadors destroyed this page! Take revenge on them!
<br /> Use <span class="label label-danger">Space</span> to shoot and <span class="label label-danger">←</span> <span class="label label-danger">→</span> to move! <button class="btn btn-default btn-xs" id="restart">Restart</button></p>
<canvas id="space-invaders" />
<link rel='stylesheet' href='https//maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css'><div id="bcl"><a style="font-size:8pt;text-decoration:none;" href="http://www.devanswer.com">Developers Answer</a></div>
<script>
(function () {
"use strict";
// General
var canvas,
screen,
gameSize,
game;
// Assets
var invaderCanvas,
invaderMultiplier,
invaderSize = 20,
initialOffsetInvader,
invaderAttackRate,
invaderSpeed,
invaderSpawnDelay = 250;
// Counter
var i = 0,
kills = 0,
spawnDelayCounter = invaderSpawnDelay;
var invaderDownTimer;
// Text
var blocks = [
[3, 4, 8, 9, 10, 15, 16],
[2, 4, 7, 11, 14, 16],
[1, 4, 7, 11, 13, 16],
[1, 2, 3, 4, 5, 7, 11, 13, 14, 15, 16, 17],
[4, 7, 11, 16],
[4, 8, 9, 10, 16]];
// Game Controller
// ---------------
var Game = function () {
this.level = -1;
this.lost = false;
this.player = new Player();
this.invaders = [];
this.invaderShots = [];
if (invaderDownTimer === undefined) {
invaderDownTimer = setInterval(function () {
for (i = 0; i < game.invaders.length; i++) game.invaders[i].move();
}, 1000 - this.level * 1.8);
};
};
Game.prototype = {
update: function () {
// Next level
if (game.invaders.length === 0) {
spawnDelayCounter += 1;
if (spawnDelayCounter < invaderSpawnDelay) return;
this.level += 1;
invaderAttackRate -= 0.002;
invaderSpeed += 10;
game.invaders = createInvaders();
spawnDelayCounter = 0;
}
if (!this.lost) {
// Collision
game.player.projectile.forEach(function (projectile) {
game.invaders.forEach(function (invader) {
if (collides(projectile, invader)) {
invader.destroy();
projectile.active = false;
}
});
});
this.invaderShots.forEach(function (invaderShots) {
if (collides(invaderShots, game.player)) {
game.player.destroy();
}
});
for (i = 0; i < game.invaders.length; i++) game.invaders[i].update();
}
// Don't stop player & projectiles.. they look nice
game.player.update();
for (i = 0; i < game.invaderShots.length; i++) game.invaderShots[i].update();
this.invaders = game.invaders.filter(function (invader) {
return invader.active;
});
},
draw: function () {
if (this.lost) {
screen.fillStyle = "rgba(0, 0, 0, 0.03)";
screen.fillRect(0, 0, gameSize.width, gameSize.height);
screen.font = "55px Lucida Console";
screen.textAlign = "center";
screen.fillStyle = "white";
screen.fillText("You lost", gameSize.width / 2, gameSize.height / 2);
screen.font = "20px Lucida Console";
screen.fillText("Points: " + kills, gameSize.width / 2, gameSize.height / 2 + 30);
} else {
screen.clearRect(0, 0, gameSize.width, gameSize.height);
screen.font = "10px Lucida Console";
screen.textAlign = "right";
screen.fillText("Points: " + kills, gameSize.width, gameSize.height - 12);
}
screen.beginPath();
var i;
this.player.draw();
if (!this.lost)
for (i = 0; i < this.invaders.length; i++) this.invaders[i].draw();
for (i = 0; i < this.invaderShots.length; i++) this.invaderShots[i].draw();
screen.fill();
},
invadersBelow: function (invader) {
return this.invaders.filter(function (b) {
return Math.abs(invader.coordinates.x - b.coordinates.x) === 0 &&
b.coordinates.y > invader.coordinates.y;
}).length > 0;
} };
// Invaders
// --------
var Invader = function (coordinates) {
this.active = true;
this.coordinates = coordinates;
this.size = {
width: invaderSize,
height: invaderSize };
this.patrolX = 0;
this.speedX = invaderSpeed;
};
Invader.prototype = {
update: function () {
if (Math.random() > invaderAttackRate && !game.invadersBelow(this)) {
var projectile = new Projectile({
x: this.coordinates.x + this.size.width / 2,
y: this.coordinates.y + this.size.height - 5 },
{
x: 0,
y: 2 });
game.invaderShots.push(projectile);
}
},
draw: function () {
if (this.active) screen.drawImage(invaderCanvas, this.coordinates.x, this.coordinates.y);
},
move: function () {
if (this.patrolX < 0 || this.patrolX > 100) {
this.speedX = -this.speedX;
this.patrolX += this.speedX;
this.coordinates.y += this.size.height;
if (this.coordinates.y + this.size.height * 2 > gameSize.height) game.lost = true;
} else {
this.coordinates.x += this.speedX;
this.patrolX += this.speedX;
}
},
destroy: function () {
this.active = false;
kills += 1;
} };
// Player
// ------
var Player = function () {
this.active = true;
this.size = {
width: 16,
height: 8 };
this.shooterHeat = -3;
this.coordinates = {
x: gameSize.width / 2 - this.size.width / 2 | 0,
y: gameSize.height - this.size.height * 2 };
this.projectile = [];
this.keyboarder = new KeyController();
};
Player.prototype = {
update: function () {
for (var i = 0; i < this.projectile.length; i++) this.projectile[i].update();
this.projectile = this.projectile.filter(function (projectile) {
return projectile.active;
});
if (!this.active) return;
if (this.keyboarder.isDown(this.keyboarder.KEYS.LEFT) && this.coordinates.x > 0) this.coordinates.x -= 2;else
if (this.keyboarder.isDown(this.keyboarder.KEYS.RIGHT) && this.coordinates.x < gameSize.width - this.size.width) this.coordinates.x += 2;
if (this.keyboarder.isDown(this.keyboarder.KEYS.Space)) {
this.shooterHeat += 1;
if (this.shooterHeat < 0) {
var projectile = new Projectile({
x: this.coordinates.x + this.size.width / 2 - 1,
y: this.coordinates.y - 1 },
{
x: 0,
y: -7 });
this.projectile.push(projectile);
} else if (this.shooterHeat > 12) this.shooterHeat = -3;
} else {
this.shooterHeat = -3;
}
},
draw: function () {
if (this.active) {
screen.rect(this.coordinates.x, this.coordinates.y, this.size.width, this.size.height);
screen.rect(this.coordinates.x - 2, this.coordinates.y + 2, 20, 6);
screen.rect(this.coordinates.x + 6, this.coordinates.y - 4, 4, 4);
}
for (var i = 0; i < this.projectile.length; i++) this.projectile[i].draw();
},
destroy: function () {
this.active = false;
game.lost = true;
} };
// Projectile
// ------
var Projectile = function (coordinates, velocity) {
this.active = true;
this.coordinates = coordinates;
this.size = {
width: 3,
height: 3 };
this.velocity = velocity;
};
Projectile.prototype = {
update: function () {
this.coordinates.x += this.velocity.x;
this.coordinates.y += this.velocity.y;
if (this.coordinates.y > gameSize.height || this.coordinates.y < 0) this.active = false;
},
draw: function () {
if (this.active) screen.rect(this.coordinates.x, this.coordinates.y, this.size.width, this.size.height);
} };
// Keyboard input tracking
// -----------------------
var KeyController = function () {
this.KEYS = {
LEFT: 37,
RIGHT: 39,
Space: 32 };
var keyCode = [37, 39, 32];
var keyState = {};
var counter;
window.addEventListener('keydown', function (e) {
for (counter = 0; counter < keyCode.length; counter++)
if (keyCode[counter] == e.keyCode) {
keyState[e.keyCode] = true;
e.preventDefault();
}
});
window.addEventListener('keyup', function (e) {
for (counter = 0; counter < keyCode.length; counter++)
if (keyCode[counter] == e.keyCode) {
keyState[e.keyCode] = false;
e.preventDefault();
}
});
this.isDown = function (keyCode) {
return keyState[keyCode] === true;
};
};
// Other functions
// ---------------
function collides(a, b) {
return a.coordinates.x < b.coordinates.x + b.size.width &&
a.coordinates.x + a.size.width > b.coordinates.x &&
a.coordinates.y < b.coordinates.y + b.size.height &&
a.coordinates.y + a.size.height > b.coordinates.y;
}
function getPixelRow(rowRaw) {
var textRow = [],
placer = 0,
row = Math.floor(rowRaw / invaderMultiplier);
if (row >= blocks.length) return [];
for (var i = 0; i < blocks[row].length; i++) {
var tmpContent = blocks[row][i] * invaderMultiplier;
for (var j = 0; j < invaderMultiplier; j++) textRow[placer + j] = tmpContent + j;
placer += invaderMultiplier;
}
return textRow;
}
// Write Text
// -----------
function createInvaders() {
var invaders = [];
var i = blocks.length * invaderMultiplier;
while (i--) {
var j = getPixelRow(i);
for (var k = 0; k < j.length; k++) {
invaders.push(new Invader({
x: j[k] * invaderSize,
y: i * invaderSize }));
}
}
return invaders;
}
// Start game
// ----------
window.addEventListener('load', function () {
var invaderAsset = new Image();
invaderAsset.onload = function () {
invaderCanvas = document.createElement('canvas');
invaderCanvas.width = invaderSize;
invaderCanvas.height = invaderSize;
invaderCanvas.getContext("2d").drawImage(invaderAsset, 0, 0);
// Game Creation
canvas = document.getElementById("space-invaders");
screen = canvas.getContext('2d');
initGameStart();
loop();
};
invaderAsset.src = "http://devanswer.com/codes/files/404-page.gif";
});
window.addEventListener('resize', function () {
initGameStart();
});
document.getElementById('restart').addEventListener('click', function () {
initGameStart();
});
function initGameStart() {
if (window.innerWidth > 1200) {
screen.canvas.width = 1200;
screen.canvas.height = 500;
gameSize = {
width: 1200,
height: 500 };
invaderMultiplier = 3;
initialOffsetInvader = 420;
} else if (window.innerWidth > 800) {
screen.canvas.width = 900;
screen.canvas.height = 600;
gameSize = {
width: 900,
height: 600 };
invaderMultiplier = 2;
initialOffsetInvader = 280;
} else {
screen.canvas.width = 600;
screen.canvas.height = 300;
gameSize = {
width: 600,
height: 300 };
invaderMultiplier = 1;
initialOffsetInvader = 140;
}
kills = 0;
invaderAttackRate = 0.999;
invaderSpeed = 20;
spawnDelayCounter = invaderSpawnDelay;
game = new Game();
}
function loop() {
game.update();
game.draw();
requestAnimationFrame(loop);
}
})();
</script>
</body>
</html>
