Building "Neon Jump": A Deep Dive into HTML5 Canvas Game Dev

In an era dominated by heavy engines like Unity, Unreal, and Godot, there is a certain romance in stripping away the bloat and writing a game engine from scratch.

Last weekend, I challenged myself to build a polished, hyper-casual platformer called "Neon Jump" in 48 hours. The constraints were simple: No engines. No libraries. No physics frameworks. Just an index.html file and a canvas tag.

The result was a game that loads in 150 milliseconds and runs at a buttery smooth 60 FPS on even low-end mobile devices. In this technical deep dive, I'm going to walk you through the architecture, the math behind the physics, and the "juice" techniques I used to make it feel professional.

1. The Architecture: The Game Loop

The heart of any game is the Loop. It is a function that runs continuously, updating the game state and drawing the frame.

Beginners often use setInterval() for this, but that is a mistake. setInterval doesn't care if the screen is ready to draw, leading to screen tearing and stuttering. The correct approach is requestAnimationFrame.

LOOP START -> UPDATE(dt) -> DRAW() -> REQUEST FRAME -> LOOP START

Here is the skeleton of our custom engine:

let lastTime = 0;

function gameLoop(timestamp) {
    const deltaTime = timestamp - lastTime;
    lastTime = timestamp;

    update(deltaTime);
    draw();

    requestAnimationFrame(gameLoop);
}

// Start the engine
requestAnimationFrame(gameLoop);
            

                Why Delta Time?
                
                Not all computers run at the same speed. If you move the player by x += 5 every frame, a player with a 144Hz monitor will move twice as fast as a player with a 60Hz monitor.
                
                By multiplying movement by deltaTime, we ensure the movement speed is consistent regardless of framerate.

2. Physics from Scratch: Euler Integration

We don't need a heavy physics library like Matter.js or Box2D for a simple jumper. We can implement basic Euler Integration.

Every object in the game (Player, Platforms, Particles) extends a basic `Entity` class with Position, Velocity, and Acceleration vectors.

The Gravity Logic

Gravity is simply a constant downward acceleration.

const GRAVITY = 0.5;
const FRICTION = 0.9;

function applyPhysics(entity) {
    // Apply Gravity
    entity.vy += GRAVITY;
    
    // Apply Velocity to Position
    entity.x += entity.vx;
    entity.y += entity.vy;

    // Apply Friction (Air resistance)
    entity.vx *= FRICTION;
    entity.vy *= FRICTION;

    // Floor Collision
    if (entity.y + entity.height > canvas.height) {
        entity.y = canvas.height - entity.height;
        entity.vy = -entity.vy * 0.6; // Bounce!
    }
}
            

3. Input Handling: Touch and Keyboard

One of the biggest challenges in HTML5 games is responsiveness. The browser sometimes lags input events. To fix this, we create an InputManager object that tracks the state of keys.

Instead of moving the player inside the event listener (which only fires once), we just toggle a boolean flag. The game loop reads that flag every frame.

const keys = {};

window.addEventListener('keydown', (e) => {
    keys[e.code] = true;
});

window.addEventListener('keyup', (e) => {
    keys[e.code] = false;
});

// Inside Update Loop
if (keys['Space'] || keys['ArrowUp']) {
    player.jump();
}
            

4. The "Juice": Making it Feel Good

A game with just squares moving around is boring. To turn "Neon Jump" into a polished experience, I implemented three key "Juice" features.

A. Particle System

Every time the player jumps or lands, I spawn 20 tiny square particles. These particles have a random velocity and a shrinking lifespan.

Optimization Tip: Creating `new Particle()` 20 times a second will trigger the Garbage Collector and cause lag. I used Object Pooling. I create 100 particles at the start of the game and recycle them. When a particle "dies," it just goes invisible and waits to be reused.

B. Squash and Stretch

This is a classic animation principle. When the player moves fast vertically, I stretch the sprite height and reduce the width. When they hit the ground, I squash the height and increase the width.

// Procedural Animation logic
player.scaleX = 1 + (Math.abs(player.vy) * 0.05);
player.scaleY = 1 - (Math.abs(player.vy) * 0.05);

ctx.save();
ctx.translate(player.x, player.y);
ctx.scale(player.scaleX, player.scaleY);
ctx.fillRect(-player.width/2, -player.height/2, player.width, player.height);
ctx.restore();
            

C. Screen Shake

When the player dies, the camera shouldn't just sit there. It should panic. I added a shake variable.

Before drawing the world, I translate the canvas context by a random amount between -shake and +shake. Every frame, I reduce shake by 10% until it reaches zero. This creates a satisfying, impactful crash effect.

5. Conclusion: Is HTML5 Viable in 2026?

Absolutely.

While Unity and Godot are powerful, they carry overhead. A Unity WebGL build takes 10-15 seconds to load on a mobile connection. "Neon Jump" loads instantly.

For hyper-casual web games, portals like Poki and CrazyGames prefer lightweight, fast-loading experiences. By going back to basics and understanding the raw math behind the engine, you not only become a better programmer, but you also gain full control over every pixel on the screen.

Experience the Engine

Reading code is one thing. Feeling the physics is another.

PLAY NEON JUMP NOW