<canvas id="particle-canvas"></canvas>
html, body {
margin: 0;
}
#particle-canvas {
width: 100%;
height: 100vh;
background: linear-gradient(to bottom, rgb(10, 10, 50) 0%,rgb(60, 10, 60) 100%);
vertical-align: middle;
}
// modified version of random-normal
function normalPool(o){var r=0;do{var a=Math.round(normal({mean:o.mean,dev:o.dev}));if(a<o.pool.length&&a>=0)return o.pool[a];r++}while(r<100)}function randomNormal(o){if(o=Object.assign({mean:0,dev:1,pool:[]},o),Array.isArray(o.pool)&&o.pool.length>0)return normalPool(o);var r,a,n,e,l=o.mean,t=o.dev;do{r=(a=2*Math.random()-1)*a+(n=2*Math.random()-1)*n}while(r>=1);return e=a*Math.sqrt(-2*Math.log(r)/r),t*e+l}
const NUM_PARTICLES = 600;
const PARTICLE_SIZE = 0.5; // View heights
const SPEED = 20000; // Milliseconds
let particles = [];
function rand(low, high) {
return Math.random() * (high - low) + low;
}
function createParticle(canvas) {
const colour = {
r: 255,
g: randomNormal({ mean: 125, dev: 20 }),
b: 50,
a: rand(0, 1),
};
return {
x: -2,
y: -2,
diameter: Math.max(0, randomNormal({ mean: PARTICLE_SIZE, dev: PARTICLE_SIZE / 2 })),
duration: randomNormal({ mean: SPEED, dev: SPEED * 0.1 }),
amplitude: randomNormal({ mean: 16, dev: 2 }),
offsetY: randomNormal({ mean: 0, dev: 10 }),
arc: Math.PI * 2,
startTime: performance.now() - rand(0, SPEED),
colour: `rgba(${colour.r}, ${colour.g}, ${colour.b}, ${colour.a})`,
}
}
function moveParticle(particle, canvas, time) {
const progress = ((time - particle.startTime) % particle.duration) / particle.duration;
return {
...particle,
x: progress,
y: ((Math.sin(progress * particle.arc) * particle.amplitude) + particle.offsetY),
};
}
function drawParticle(particle, canvas, ctx) {
canvas = document.getElementById('particle-canvas');
const vh = canvas.height / 100;
ctx.fillStyle = particle.colour;
ctx.beginPath();
ctx.ellipse(
particle.x * canvas.width,
particle.y * vh + (canvas.height / 2),
particle.diameter * vh,
particle.diameter * vh,
0,
0,
2 * Math.PI
);
ctx.fill();
}
function draw(time, canvas, ctx) {
// Move particles
particles.forEach((particle, index) => {
particles[index] = moveParticle(particle, canvas, time);
})
// Clear the canvas
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Draw the particles
particles.forEach((particle) => {
drawParticle(particle, canvas, ctx);
})
// Schedule next frame
requestAnimationFrame((time) => draw(time, canvas, ctx));
}
function initializeCanvas() {
let canvas = document.getElementById('particle-canvas');
canvas.width = canvas.offsetWidth * window.devicePixelRatio;
canvas.height = canvas.offsetHeight * window.devicePixelRatio;
let ctx = canvas.getContext("2d");
window.addEventListener('resize', () => {
canvas.width = canvas.offsetWidth * window.devicePixelRatio;
canvas.height = canvas.offsetHeight * window.devicePixelRatio;
ctx = canvas.getContext("2d");
})
return [canvas, ctx];
}
function startAnimation() {
const [canvas, ctx] = initializeCanvas();
// Create a bunch of particles
for (let i = 0; i < NUM_PARTICLES; i++) {
particles.push(createParticle(canvas));
}
requestAnimationFrame((time) => draw(time, canvas, ctx));
};
// Start animation when document is loaded
(function () {
if (document.readystate !== 'loading') {
startAnimation();
} else {
document.addEventListener('DOMContentLoaded', () => {
startAnimation();
})
}
}());
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