engine.js

// Physics constants.
var XV_ACCELERATION = 0.085;
var XV_TERMINAL = 0.6;
var XV_FRICTION = 0.05;
var YV_GRAVITY = 0.05;
var YV_TERMINAL = 100;
var XV_BULLET = 0.75;

// Jumping physics constants
var JUMP = 0.9;
var JUMP_MAX = 2;
var JUMP_COOLDOWN = 400;
var CLIP_THRESHOLD = 2;

// Particle constants
var XV_PARTICLE = 0.5;
var YV_PARTICLE = 1;
var PARTICLE_TIMEOUT = 5000;

// Player constants
var MAX_BULLETS = 2;
var BULLET_COOLDOWN = 200;
var INVINCIBILITY_TIME = 2000;
var SHIELD_TIME = 2000;

var MAP_TIME = 500;

// Platform constants.
PLATFORM_THICKNESS = 4;

// Animation limits.
var FPS_CAP = 100;
var FPS_INTERVAL = 1000 / FPS_CAP;
var F = 0;
var S = 0;

var units = [
    "pole", "pound", "square meter", "second", "hour", "year", "decade", "mile", "stade", "acre", "dollar", "cookie", "frame", 
    "cubic millimeter", "quartic cubit", "object", "coffee", "error", "failure", "mistake", "exception", "warning", "point",
    "gallon", "ounce", "gram", "kilograms", "decibal", "tonne", "ton", "furlong", "fortnight", "firkin"
];
var unit = " " + units[Math.floor(Math.random()*units.length)] + "s/" + units[Math.floor(Math.random()*units.length)];

window.onfocus = function() { F = 0; S = Date.now() ; }

// Input.
var keys = {};
var keymap = [
	{left: 65, right: 68, up: 87, down: 83, shoot: 49, shield: 192},
	{left: 37, right: 39, up: 38, down: 40, shoot: 220, shield: 221}
];

// Sprites and particles.
var spritesPaths = {zero: "images/zero.png", infinity: "images/infinity.png", ddx: "images/ddx.png", intsmall: "images/intsmall.png", intlarge: "images/intlarge.png"}
var spritesReady = {}
var sprites = {};

for (var key in spritesPaths) {
    spritesReady[key] = false;
    
    var image = new Image();
    image.key = key;
    image.onload = function() { spritesReady[this.key] = true; }
    image.src = spritesPaths[key];
    
    sprites[key] = image;
}

var particlePaths = ["images/particle/0.png", "images/particle/1.png", "images/particle/2.png", "images/particle/3.png", "images/particle/4.png", "images/particle/5.png", "images/particle/6.png", "images/particle/7.png", "images/particle/8.png", "images/particle/9.png"];
var particlesReady = [];
var particles = [];

for (var i = 0; i < particlePaths.length; i++) {
	particlesReady[i] = false;
	
	var image = new Image();
	image.key = i;
    image.onload = function() { particlesReady[this.key] = true; }
    image.src = particlePaths[i];
    
    particles[i] = image;
}

var ready = false;

// Animation
var w = window;
requestAnimationFrame = w.requestAnimationFrame || w.webkitRequestAnimationFrame || w.msRequestAnimationFrame || w.mozRequestAnimationFrame;

// Rectangular intersection.
function intersects(r1, r2) {
    return !(r1[0]+r1[2] < r2[0] || r1[0] > r2[0]+r2[2] || r1[1]+r1[3] < r2[1] || r1[1] > r2[1]+r2[3]);
}

// The main game engine class.
function Engine(canvas) {
    
    // Graphics.
    this.canvas = canvas;
    this.context = canvas.getContext("2d");
    this.context.font = "20px Verdana";

    // Set up timing.
    this.time = Date.now();

    // Input binding.
    addEventListener("keydown", function(e) { 
        keys[e.keyCode] = true; 
        if ([37, 39, 38, 40].indexOf(e.keyCode) > -1) e.preventDefault();
    }, false);
    addEventListener("keyup", function(e) { delete keys[e.keyCode]; }, false);

    // Game objects.
    this.map = 1;
	this.maps = [
		{
			platforms: [
				new Platform((canvas.width - 400)/2, canvas.height * 13/20, 400, PLATFORM_THICKNESS), 
				new Platform((canvas.width - 650)/2, canvas.height * 9/20, 150, PLATFORM_THICKNESS), 
				new Platform((canvas.width + 350)/2, canvas.height * 9/20, 150, PLATFORM_THICKNESS),
				new Platform((canvas.width - 100)/2, canvas.height * 17/20, 100, PLATFORM_THICKNESS)
			],
            spawns: {
				zero: 100,
				infinitus: canvas.width - 100
			}
		},
		{
			platforms: [
				new Platform((canvas.width - 20)/2, canvas.height * 9/20, 20, PLATFORM_THICKNESS)
			],
			spawns: {
				zero: canvas.width / 2,
				infinitus: canvas.width / 2
			}
		},
        {
            platforms: [
                new Platform(canvas.width * 1/5, canvas.height * 9/20, canvas.width * 3/5, PLATFORM_THICKNESS)
            ],
            spawns: {
                zero: canvas.width * 3/10,
                infinitus: canvas.width * 7/10
            }
        },
        {
            platforms: [
                new Platform(canvas.width * 2/5, canvas.height * 9/20, canvas.width * 1/5, PLATFORM_THICKNESS),
                new Platform(canvas.width * 1/5, canvas.height * 13/20, canvas.width * 3/5, PLATFORM_THICKNESS),
                new Platform(canvas.width * 2/5, canvas.height * 17/20, canvas.width * 1/5, PLATFORM_THICKNESS)
            ],
            spawns: {
                zero: canvas.width * 3/10,
                infinitus: canvas.width * 7/10
            }
        }
	];
	this.mapTime = 0;
    
    this.bullets = [];
    this.players = {
        zero: new Player("zero", sprites.zero, sprites.intlarge, particles, keymap[0], this),
        infinitus: new Player("infinitus", sprites.infinity, sprites.intsmall, particles, keymap[1], this)
    };
        
    this.players.zero.x = 100;
    this.players.zero.direction = 1;
    this.players.infinitus.x = this.canvas.width - 100 - this.players.infinitus.image.width;
                
    // Update the game.
    this.update = function(delta) {
    
    	if (77 in keys) { this.setMap(this.map+1); }
 
        // Update the players
        for (var name in this.players) this.players[name].update(delta);
        for (var i = 0; i < this.bullets.length; i++) {
            var bullet = this.bullets[i];
            bullet.update(delta);
            
            // Check if a bullet has died.
            if (bullet.x+bullet.image.width < 0 || bullet.x > canvas.width) {
                this.dieBullet(i);
            }
        }
        
        // Collision detection
        for (var name in this.players) {
            
            // Get the actual player.
            var player = this.players[name];
            
            // Generate boundary boxes.
            var bbox = player.bbox();
            
            // Platform collision.
            player.grounded = false;
            for (var i = 0; i < this.platforms.length; i++) {
                
                // Access the individual platform. 
                var platform = this.platforms[i];
                
                // Check if colliding with platform while FALLING.
                if (player.yv > 0 && intersects(bbox, platform.bbox()) && !(i in player.collisions)) {
                    //console.log(platform.bbox());
                    player.y = platform.y - player.image.height;
                    player.yv = 0;
                    player.grounded = true;
                    player.jump = 0;
                    player.collisions[i] = true;
                } else {
                    delete player.collisions[i];
                }
                
            }
            
            for (var i = 0; i < this.bullets.length; i++) {
                
                // Access the bullet.
                var bullet = this.bullets[i];
                
                // Intersection with bullet.
                if (!player.invincible() && !player.shielded && intersects(bbox, bullet.bbox())) {
                    this.die(player);
                    this.dieBullet(i);
                } else if (player.shielded && intersects(bbox, bullet.bbox())) {
                    this.dieBullet(i);
                }
                
            }
            
            // Edge detection.
            if (player.x < 0) player.x = 0;
            else if (player.x+player.image.width > canvas.width) player.x = canvas.width - player.image.width;
            if (player.y < 0) player.y = 0;
            else if (player.y + player.image.height > canvas.height + 150) this.die(player);

        }
        
    }
    
    // Draw the game to the canvas. 
    this.render = function() {
        
        // Check if reasources are ready.
        if (!ready) {
            ready = true;
            for (var key in spritesReady) ready &= spritesReady[key];
            return;
        }
		        
        // Redraw the background.
        this.context.fillStyle = "#CCC";
        this.context.fillRect(0, 0, this.canvas.width, this.canvas.height);
        
        // Draw the platforms.
        this.context.fillStyle = "#000";
        for (var i = 0; i < this.platforms.length; i++) {
            this.platforms[i].render(this.context);
        }
        
        // Draw the players.
        for (var name in this.players) {
            this.players[name].render(this.context);
        }
        
        // Draw the bullets.
        for (var i = 0; i < this.bullets.length; i++) {
            this.bullets[i].render(this.context);
        }
        
        // Draw frames per second.
        this.context.fillStyle = "#AAA";
        
        this.context.textAlign = "left";
        this.context.textBaseline = "top";
        this.context.fillText(Math.round(F/(Date.now() - S) * 1000) + unit, 10, 10);
        
        this.context.fillRect(10, this.canvas.height-40, 0.1*this.players.zero.shield, 3);
        this.context.textBaseline = "bottom"
        this.context.fillText("Captain Zero: " + this.players.zero.score, 10, this.canvas.height-10);

        this.context.fillRect(this.canvas.width-10, this.canvas.height-40, -0.1*this.players.infinitus.shield, 3);
        this.context.textAlign = "right";
        this.context.fillText("Infinitus: " + this.players.infinitus.score, this.canvas.width-10, this.canvas.height-10);

        this.context.textBaseline = "top";
		this.context.fillText("(m) Map " + (this.map+1), this.canvas.width-10, 10);

    }
        
    // The main game loop.
    this.main = function() {
        		
        // Record timing.
        var now = Date.now();
        var delta = now - this.time;
        
        if (delta > FPS_INTERVAL) {
        
            // Update and render.
            this.update(delta);
            this.render();

            // Update timing.
            this.time = now;
            
            // Update frame count.
            F++;
        
        }
            
        // Next frame
        requestAnimationFrame(this.main.bind(this));
        
    }
    
    // Called when a player dies.
    this.die = function(player) {
        
        // Move the player and update score.
        if (player.name == "zero") this.players.infinitus.score++;
        else if (player.name == "infinitus") this.players.zero.score++;
        player.die();
        
    }
    
    // Wait for resources before going to main.
    this.start = function() {
        S = Date.now();
		this.setMap(0);
        this.main(); 
    }
    
    // Kill a bullet.
    this.dieBullet = function(index) {
        this.bullets[index].player.bullet++;
        this.bullets.splice(index, 1);
    }
    
    this.setMap = function(index) {
    	if (Date.now() - this.mapTime < MAP_TIME) return;
    	
    	this.map = index % this.maps.length;
    	
    	this.platforms = this.maps[this.map].platforms;
    	this.players.zero.respawn();
    	this.players.infinitus.respawn();
    	this.players.zero.x = this.maps[this.map].spawns.zero - this.players.zero.image.width / 2;
    	this.players.infinitus.x = this.maps[this.map].spawns.infinitus - this.players.infinitus.image.width / 2;
    	this.mapTime = Date.now();
    }
    
}

// Start the game.
function start() {
    var canvas = document.getElementById("canvas");
    var e = new Engine(canvas);
    e.start();
}