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html5 canvas 英雄打怪小游戏

2014-04-18 09:08 423 查看
具体参考:

http://www.lostdecadegames.com/how-to-make-a-simple-html5-canvas-game/



// Create the canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 512;
canvas.height = 480;
document.body.appendChild(canvas);

// Background image
var bgReady = false;
var bgImage = new Image();
bgImage.onload = function () {
bgReady = true;
};
bgImage.src = "images/background.png";

// Hero image
var heroReady = false;
var heroImage = new Image();
heroImage.onload = function () {
heroReady = true;
};
heroImage.src = "images/hero.png";

// Monster image
var monsterReady = false;
var monsterImage = new Image();
monsterImage.onload = function () {
monsterReady = true;
};
monsterImage.src = "images/monster.png";

// Game objects
var hero = {
speed: 256 // movement in pixels per second
};
var monster = {
speed: 128 // we let monster go.
};
var monstersCaught = 0;

// Handle keyboard controls
var keysDown = {};

addEventListener("keydown", function (e) {
keysDown[e.keyCode] = true;
}, false);

addEventListener("keyup", function (e) {
delete keysDown[e.keyCode];
}, false);

// Reset the game when the player catches a monster
var reset = function () {
hero.x = canvas.width / 2;
hero.y = canvas.height / 2;

// Throw the monster somewhere on the screen randomly
monster.x = 32 + (Math.random() * (canvas.width - 64));
monster.y = 32 + (Math.random() * (canvas.height - 64));
};

var flagx = 1;
var flagy = 1;

// Update game objects
var update = function (modifier) {
if (38 in keysDown) { // Player holding up
hero.y -= hero.speed * modifier;
}
if (40 in keysDown) { // Player holding down
hero.y += hero.speed * modifier;
}
if (37 in keysDown) { // Player holding left
hero.x -= hero.speed * modifier;
}
if (39 in keysDown) { // Player holding right
hero.x += hero.speed * modifier;
}

//Here we let the monster go

if(monster.x <= 0){
flagx = 1;
}else if(monster.x >= canvas.width){
flagx = -1;
}

if(monster.y <= 0){
flagy = 1;
}else if(monster.y >= canvas.height){
flagy = -1;
}

monster.x = monster.x + monster.speed * modifier * flagx;

monster.y = monster.y + monster.speed * modifier * flagy;

// Are they touching?
if (
hero.x <= (monster.x + 32)
&& monster.x <= (hero.x + 32)
&& hero.y <= (monster.y + 32)
&& monster.y <= (hero.y + 32)
) {
++monstersCaught;
reset();
}
};

// Draw everything
var render = function () {
if (bgReady) {
ctx.drawImage(bgImage, 0, 0);
}

if (heroReady) {
ctx.drawImage(heroImage, hero.x, hero.y);
}

if (monsterReady) {
ctx.drawImage(monsterImage, monster.x, monster.y);
}

// Score
ctx.fillStyle = "rgb(250, 250, 250)";
ctx.font = "24px Helvetica";
ctx.textAlign = "left";
ctx.textBaseline = "top";
ctx.fillText("Goblins caught: " + monstersCaught, 32, 32);
};

// The main game loop
var main = function () {
var now = Date.now();
var delta = now - then;

update(delta / 1000);
render();

then = now;
};

// Let's play this game!
reset();
var then = Date.now();
setInterval(main, 1); // Execute as fast as possible


 
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