body{
margin: 0;
overflow: hidden;
}
const width = document.getElementById("myCanvas").width = screen.availWidth;
const height = document.getElementById("myCanvas").height = screen.availHeight;
const ctx = document.getElementById("myCanvas").getContext("2d");
const arr = Array(Math.ceil(width / 10)).fill(0);
const str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".split("");
function rain() {
ctx.fillStyle = "rgba(0,0,0,0.05)";
ctx.fillRect(0, 0, width, height);
ctx.fillStyle = "#0f0";
arr.forEach(function (value, index) {
ctx.fillText(str[Math.floor(Math.random() * str.length)], index * 10, value + 10);
arr[index] = value >= height || value > 8888 * Math.random() ? 0 : value + 10;
});
}
setInterval(rain, 30);