HTML5 Game Development – Lesson 6

HTML5 Game Development – Lesson 6

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HTML5 Game Development - Lesson 6

HTML5 Game Development – Lesson 6

This is our next game development article. We continue a series of articles on game development in HTML5 using canvas. Today this is quite complete game example – it will reincarnation of old computer game – Battle City. I will teach you to use alternative array-maps plus I will show – how to detect collision of active object (Tank) with environment (array based map).

Here you can read our previous lesson: Developing Your First HTML5 Game – Lesson 5.

Here are our demo and downloadable package:

Live Demo
download in package

Ok, download the example files and lets start coding !


Step 1. HTML

As always – very small HTML markup.

index.html

<!DOCTYPE html>
<html lang="en" >
<head>
<meta charset="utf-8" />
<title>HTML5 Game Development - Lesson 6 | Script Tutorials</title>
<link href="css/main.css" rel="stylesheet" type="text/css" />
<script src="js/jquery-1.5.2.min.js"></script>
<script src="js/script.js"></script>
</head>
<body>
<header>
<h2>HTML5 Game Development - Lesson 6</h2>
<a href="https://www.script-tutorials.com/html5-game-development-lesson-6/" class="stuts">Back to original tutorial on <span>Script Tutorials</span></a>
</header>
<div class="container">
<canvas id="scene" width="800" height="600"></canvas>
</div>
</body>
</html>

Step 2. CSS

css/main.css

I won’t publish CSS styles today, there are only a few page layout styles. You can find this file in our package.

Step 3. JS

js/jquery-1.5.2.min.js

We use jQuery for our lesson. Available in package. Next file most important (here are all our html5 functional):

js/script.js

// inner variables
var canvas, context; // canvas and context objects
var imgBrick, imgSteel, imgWater, imgForest, imgTank; // images
var aMap; // map array
var oTank; // tank object
var iCellSize = 24; // cell wide
var iXCnt = 26; // amount of X cells
var iYCnt = 26; // amount of Y cells
// objects :
function Tank(x, y, w, h, image) {
this.x = x;
this.y = y;
this.w = w;
this.h = h;
this.i = 0;
this.image = image;
}
// functions
function clear() { // clear canvas function
context.clearRect(0, 0, canvas.width, canvas.height);
}
function drawScene() { // main drawScene function
clear(); // clear canvas
// fill background
context.fillStyle = '#111';
context.fillRect(0, 0, canvas.width, canvas.height);
// save current context
context.save();
// walk through our array
for (var y = 0; y < iYCnt; y++) { 
for (var x = 0; x < iXCnt; x++) {
switch (aMap[y][x]) {
case 0: // skip
break;
case 1: // draw brick block
context.drawImage(imgBrick, 0, 0, iCellSize, iCellSize, x*iCellSize, y*iCellSize, iCellSize, iCellSize);
break;
case 2: // draw steel block
context.drawImage(imgSteel, 0, 0, iCellSize, iCellSize, x*iCellSize, y*iCellSize, iCellSize, iCellSize);
break;
case 3: // draw forest block
context.drawImage(imgForest, 0, 0, iCellSize, iCellSize, x*iCellSize, y*iCellSize, iCellSize, iCellSize);
break;
case 4: // draw water block
context.drawImage(imgWater, 0, 0, iCellSize, iCellSize, x*iCellSize, y*iCellSize, iCellSize, iCellSize);
break;
}
}
}
// restore current context
context.restore();
// draw tank
context.drawImage(oTank.image, oTank.i*oTank.w, 0, oTank.w, oTank.h, oTank.x, oTank.y, oTank.w, oTank.h);
}
// -------------------------------------------------------------
// initialization
$(function(){
canvas = document.getElementById('scene');
canvas.width  = iXCnt * iCellSize;
canvas.height = iYCnt * iCellSize;
context = canvas.getContext('2d');
// main scene Map array
aMap = ([
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0],
[0, 0, 1, 1, 4, 4, 4, 4, 0, 0, 2, 2, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 4, 4, 4, 4, 0, 0, 2, 2, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 4, 4, 4, 4, 1, 1, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 0, 0, 2, 2, 0, 0],
[0, 0, 0, 0, 4, 4, 4, 4, 1, 1, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 0, 0, 2, 2, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 1, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 1, 1, 0, 0, 0, 0],
[0, 0, 2, 2, 0, 0, 0, 0, 4, 4, 4, 4, 0, 0, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 2, 2, 0, 0, 0, 0, 4, 4, 4, 4, 0, 0, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[3, 3, 3, 3, 1, 1, 0, 0, 4, 4, 4, 4, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0],
[3, 3, 3, 3, 1, 1, 0, 0, 4, 4, 4, 4, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0],
[3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 0, 0, 0, 0, 2, 2],
[3, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 0, 0, 0, 0, 2, 2],
[0, 0, 1, 1, 4, 4, 4, 4, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 1, 1, 4, 4, 4, 4, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[2, 2, 0, 0, 4, 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 3, 3, 0, 0, 1, 1, 0, 0],
[2, 2, 0, 0, 4, 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 3, 3, 3, 3, 0, 0, 1, 1, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 0, 0, 4, 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 0, 0, 4, 4, 4, 4, 3, 3, 3, 3, 4, 4, 4, 4, 0, 0],
[0, 0, 0, 0, 0, 0, 2, 2, 3, 3, 0, 0, 0, 0, 0, 0, 3, 3, 3, 3, 4, 4, 4, 4, 0, 0],
[0, 0, 0, 0, 0, 0, 2, 2, 3, 3, 0, 0, 0, 0, 0, 0, 3, 3, 3, 3, 4, 4, 4, 4, 0, 0],
[0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 2, 2, 0, 0, 0, 0],
[1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 2, 2, 0, 0, 0, 0]
]);
// load images
imgBrick = new Image();
imgBrick.src = 'images/brick.png';
imgSteel = new Image();
imgSteel.src = 'images/steel.png';
imgWater = new Image();
imgWater.src = 'images/water.png';
imgForest = new Image();
imgForest.src = 'images/forest.png';
imgTank = new Image();
imgTank.src = 'images/tank.png';
oTank = new Tank(iCellSize*9, iCellSize*24, 48, 48, imgTank);
$(window).keydown(function(event){ // keyboard alerts
switch (event.keyCode) {
case 38: // Up key
oTank.i = 2;
// checking collisions
var iCurCelX = (2 * oTank.x) / 48;
var iCurCelY = (2 * oTank.y) / 48;
if (iCurCelY) {
var iTest1 = aMap[iCurCelY-1][iCurCelX];
var iTest2 = aMap[iCurCelY-1][iCurCelX+1];
if ((iTest1 == 0 || iTest1 == 3) && (iTest2 == 0 || iTest2 == 3)) {
oTank.y-=24;
if (oTank.y < 0) {
oTank.y = 0;
}
}
}
break;
case 40: // Down key
oTank.i = 3;
// checking collisions
var iCurCelX = (2 * oTank.x) / 48;
var iCurCelY = (2 * oTank.y) / 48;
if (iCurCelY+2 < iYCnt) {
var iTest1 = aMap[iCurCelY+2][iCurCelX];
var iTest2 = aMap[iCurCelY+2][iCurCelX+1];
if ((iTest1 == 0 || iTest1 == 3) && (iTest2 == 0 || iTest2 == 3)) {
oTank.y+=24;
if (oTank.y > 576) { //iCellSize * (iYCnt-2)
oTank.y = 576;
}
}
}
break;
case 37: // Left key
oTank.i = 1;
// checking collisions
var iCurCelX = (2 * oTank.x) / 48;
var iCurCelY = (2 * oTank.y) / 48;
var iTest1 = aMap[iCurCelY][iCurCelX-1];
var iTest2 = aMap[iCurCelY+1][iCurCelX-1];
if ((iTest1 == 0 || iTest1 == 3) && (iTest2 == 0 || iTest2 == 3)) {
oTank.x-=24;
if (oTank.x < 0) {
oTank.x = 0;
}
}
break;
case 39: // Right key
oTank.i = 0;
// checking collisions
var iCurCelX = (2 * oTank.x) / 48;
var iCurCelY = (2 * oTank.y) / 48;
var iTest1 = aMap[iCurCelY][iCurCelX+2];
var iTest2 = aMap[iCurCelY+1][iCurCelX+2];
if ((iTest1 == 0 || iTest1 == 3) && (iTest2 == 0 || iTest2 == 3)) {
oTank.x+=24;
if (oTank.x > 576) { //iCellSize * (iXCnt-2)
oTank.x = 576;
}
}
break;
}
});
setInterval(drawScene, 40); // loop drawScene
});

I have added my comments everywhere, hope that all this code is pretty understandable.


Live Demo
download in package

Conclusion

Today, we have made quite complete HTML5 game – BattleCity. I will be glad to see your thanks and comments. Good luck!

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