JSFiddle - React, Tailwind, and code Playground

by spmbt

HTML

<canvas id="canvas"></canvas><br>
&nbsp;<button>Toggle Motion</button>

CSS

body {
	margin: 0; background: #4b7299; height: 100%;
}
#canvas {
  width: 100%; background: #6b92b9; 
}

JavaScript

//canvas init
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

//canvas dimensions
var W = window.innerWidth;
var H = window.innerHeight;
canvas.width = W;
canvas.height = H;

//snowflake particles
var mp = 25; //max particles
var particles = [];
for(var i = 0; i < mp; i++)
{
  particles.push({
    x: Math.random()*W, //x-coordinate
    y: Math.random()*H, //y-coordinate
    r: Math.random()*4+1, //radius
    d: Math.random()*mp //density
  })
}

//Lets draw the flakes
function draw()
{count++;
  ctx.clearRect(0, 0, W, H);

  ctx.fillStyle = "rgba(255, 255, 255, 0.8)";
  ctx.beginPath();
  for(var i = 0; i < mp; i++)
  {
    var p = particles[i];
    ctx.moveTo(p.x, p.y);
    ctx.arc(p.x, p.y, p.r, 0, Math.PI*2, true);
  }
  ctx.fill();
  update();
}

//Function to move the snowflakes
//angle will be an ongoing incremental flag. Sin and Cos functions will be applied to it to create vertical and horizontal movements of the flakes
var angle = 0;
function update()
{
  angle += 0.01;
  for(var i = 0; i < mp; i++)
  {
    var p = particles[i];
    //Updating X and Y coordinates
    //We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards
    //Every particle has its own density which can be used to make the downward movement different for each flake
    //Lets make it more random by adding in the radius
    p.y += Math.cos(angle+p.d) + 1 + p.r/2;
    p.x += Math.sin(angle) * 2;

    //Sending flakes back from the top when it exits
    //Lets make it a bit more organic and let flakes enter from the left and right also.
    if(p.x > W+5 || p.x < -5 || p.y > H)
    {
      if(i%3 > 0) //66.67% of the flakes
      {
        particles[i] = {x: Math.random()*W, y: -10, r: p.r, d: p.d};
      }
      else
      {
        //If the flake is exitting from the right
        if(Math.sin(angle) > 0)
        {
          //Enter from the left
          particles[i] = {x: -5, y: Math.random()*H, r: p.r,...