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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <html>
    <body>
        <canvas id="canvas-bg"></canvas>
        <main id="main">
            <h1 id="title" class="sans-serif">Changing color title</h1>
            <div class="sans-serif"><input type="checkbox" id="switch" onclick="handleClick(event)"/>Switch Bulb</div>
        </main>
    </body>
</html>
!

CSS 

              
                :root {
    --dark-color: #040020;
    --light-color: #fff;
}

body {
    background-color: var(--dark-color);
    margin: 0;
}

main {
    display: flex;
    justify-content: center;
    padding: 10px;
}

#canvas-bg {
    position: fixed;
    z-index: -1;
    width: 100%;
    height: 100%;
}

.sans-serif {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

h1 {
    transition: all .5s;
}

.dark *{
    color: var(--dark-color);
}

.light *{
    color: var(--light-color);
}
!

JS 

              
                const dark_color =  "#040020", light_color = "#fff";
let animationCount = 0;
const speed = 10;
const clickPosition = {x: 0, y: 0};

const switchBulb = document.getElementById("switch");
let lightOn = switchBulb.checked;

let canvas = document.getElementById("canvas-bg");
let ctx = canvas.getContext("2d");

function handleClick(e) {
    lightOn = switchBulb.checked;
    clickPosition.x = e.x;
    clickPosition.y = e.y;
    if(lightOn) turnOn();
    else turnOff();
    changeContent();
}

function resizeCanvas(){
    ctx.canvas.width  = window.innerWidth;
    ctx.canvas.height = window.innerHeight;
    ctx.fillStyle = lightOn ? light_color : dark_color;
    ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
};
window.addEventListener("resize", resizeCanvas);
resizeCanvas(); //resize first time to screen

function changeContent(){
    let main = document.getElementById("main");
    main.classList.add(lightOn ? "dark" : "light"); // if light is on, content is dark
    main.classList.remove(lightOn ? "light" : "dark"); // remove old class if present
}
changeContent(); //coloring content first time

function turnOn() {
    if(animationCount === 0) switchBulb.disabled = true;
    let pixelRadius = animationCount * speed;
    ctx.fillStyle = dark_color;
    ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
    ctx.beginPath();
    ctx.arc(clickPosition.x, clickPosition.y, pixelRadius, 0, 2 * Math.PI, true);
    ctx.fillStyle = light_color;
    ctx.fill();
    animationCount++;
    if(pixelRadius < (Math.sqrt(Math.pow(ctx.canvas.width,2) + Math.pow(ctx.canvas.height,2))+ 200)){
        setTimeout(turnOn, 1);
    } else {
        animationCount = 0;
        switchBulb.disabled = false;
    }
}

function turnOff() {
    let pixelRadius = animationCount * speed;
    if(animationCount === 0) {
        switchBulb.disabled = true;
        pixelRadius = (Math.sqrt(Math.pow(ctx.canvas.width,2) + Math.pow(ctx.canvas.height,2))+ 200);
        animationCount = Math.ceil(pixelRadius / speed);
    }
    ctx.fillStyle = dark_color;
    ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
    ctx.beginPath();
    ctx.arc(clickPosition.x, clickPosition.y, pixelRadius, 0, 2 * Math.PI, true);
    ctx.fillStyle = light_color;
    ctx.fill();
    animationCount--;
    if(animationCount > 0) setTimeout(turnOff, 1);
    else {
        ctx.fillStyle = dark_color;
        ctx.fillRect(0, 0, ctx.canvas.width, canvas.height);
        switchBulb.disabled = false;
    }
}
!
999px

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