How to build a JavaScript-based 2D platform game?
13/03/2024
•
5
min
Building a 2D platform game in JavaScript involves a number of steps such as creating the HTML framework, setting up the game canvas, creating game characters, controlling animations, incorporating sound effects, and more. Below is a general step-by-step guide:
NB: The code might look big from the outside but it's actually easier if you take it one step at a time. Do not rush the process.
Step 1. Create the HTML Markup
First things first, we need to create a `canvas` where our game will live. An HTML document only needs a canvas element to get started.
\`\`\`html
<!DOCTYPE html>
<html>
<head>
<title>2D Platform Game</title>
<style>
canvas {
border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="gameCanvas" width="800" height="400"></canvas>
<script src="game.js"></script>
</body>
</html>
\`\`\`
This creates a canvas of 800 pixels wide and 400 pixels tall, and includes a JavaScript file `game.js` where we'll put our game code.
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Step 2. Set up the Game Canvas
Inside `game.js`, we start by getting a reference to the canvas and its context which we will use to draw onto it.
\`\`\`javascript
var canvas = document.getElementById('gameCanvas');
var ctx = canvas.getContext('2d');
\`\`\`
Step 3. Creating the Game Character
For simplicity, our game character will be a rectangle. We'll need to define properties like width, height, position, and velocity.
\`\`\`javascript
var player = {
x: 100,
y: 100,
width: 50,
height: 50,
color: '#ff0000',
dy: 0, // vertical velocity
jumpForce: 10,
grounded: false
}
\`\`\`
Then, we need a function to draw the player onto the canvas.
\`\`\`javascript
function drawPlayer() {
ctx.fillStyle = player.color;
ctx.fillRect(player.x, player.y, player.width, player.height);
};
drawPlayer();
\`\`\`
Step 4. Animating the Game Character
To make our game dynamic, we need to animate the player. This typically involves updating the game state and then rendering it, over and over again.
\`\`\`javascript
function update() {
// game update logic
// player gravity
if(player.y + player.height < canvas.height){
player.dy++;
} else {
player.y = canvas.height - player.height;
player.dy = 0;
player.grounded = true;
}
player.y += player.dy;
// draw after update
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawPlayer();
requestAnimationFrame(update);
}
update();
\`\`\`
Step 5. Controlling the Character
The last thing will be to add some control to the character.
\`\`\`javascript
window.addEventListener('keydown', function(e){
if(e.key === " " && player.grounded){
player.dy = -player.jumpForce;
player.grounded = false;
}
});
\`\`\`
This will make the character jump when the spacebar key is pressed.
This is a very basic example to get started with 2D game development in JavaScript. You would need additional concepts like collision detection, multiple game objects, sound effects, game scoring and more to create a full-featured game. Remember to practice and have fun in the process!
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