<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>烟花特效</title><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.2/css/fontawesome.min.css"><link rel="stylesheet" href="./style.css">
</head>
<body><canvas></canvas><h1>202<span class="pen">4</span> 新年快乐😃</h1><script src="./script.js"></script>
</body>
</html>
var ctx = document.querySelector('canvas').getContext('2d')
ctx.canvas.width = window.innerWidth
ctx.canvas.height = window.innerHeightvar sparks = []
var fireworks = []
var i = 20; while(i--) {fireworks.push(new Firework(Math.random()*window.innerWidth, window.innerHeight*Math.random()))
}render()
function render() {setTimeout(render, 1000/60)ctx.fillStyle = 'rgba(0, 0, 0, 0.1)';ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height)for(var firework of fireworks) {if(firework.dead) continuefirework.move()firework.draw()}for(var spark of sparks) {if(spark.dead) continuespark.move()spark.draw()}if(Math.random() < 0.05) {fireworks.push(new Firework())}
}function Spark(x, y, color) {this.x = xthis.y = ythis.dir = Math.random() * (Math.PI*2)this.dead = falsethis.color = colorthis.speed = Math.random() * 3 + 3;this.walker = new Walker({ radius: 20, speed: 0.25 })this.gravity = 0.25this.dur = this.speed / 0.1this.move = function() {this.dur--if(this.dur < 0) this.dead = trueif(this.speed < 0) returnif(this.speed > 0) this.speed -= 0.1var walk = this.walker.step()this.x += Math.cos(this.dir + walk) * this.speedthis.y += Math.sin(this.dir + walk) * this.speedthis.y += this.gravitythis.gravity += 0.05}this.draw = function() {drawCircle(this.x, this.y, 3, this.color)}
}function Firework(x, y) {this.xmove = new Walker({radius: 10, speed: 0.5})this.x = x || Math.random() * ctx.canvas.widththis.y = y || ctx.canvas.heightthis.height = Math.random()*ctx.canvas.height/2this.dead = falsethis.color = randomColor()this.move = function() {this.x += this.xmove.step()if(this.y > this.height) this.y -= 1; else this.burst()}this.draw = function() {drawCircle(this.x, this.y, 1, this.color)}this.burst = function() {this.dead = truevar i = 100; while(i--) sparks.push(new Spark(this.x, this.y, this.color))}
}function drawCircle(x, y, radius, color) {color = color || '#FFF'ctx.fillStyle = colorctx.fillRect(x-radius/2, y-radius/2, radius, radius)
}function randomColor(){return ['#93c47d','#a4c2f4','#b4a7d6','#c27ba0','#f6b26b', '#ffd966'][Math.floor(Math.random() * 6)];
}function Walker(options){this.step = function(){this.direction = Math.sign(this.target) * this.speedthis.value += this.directionthis.target? this.target -= this.direction: (this.value)? (this.wander) ? this.target = this.newTarget() : this.target = -this.value: this.target = this.newTarget() return this.direction}this.newTarget = function() {return Math.round(Math.random()*(this.radius*2)-this.radius)}this.start = 0this.value = 0this.radius = options.radiusthis.target = this.newTarget()this.direction = Math.sign(this.target)this.wander = options.wanderthis.speed = options.speed || 1
}
html, body {padding: 0px;margin: 0px;background: #222;font-family: 'Karla', sans-serif;color: #fff;height: 100%;overflow: hidden;
}h1 {z-index: 1000;position: fixed;top: 50%;left: 50%;transform: translateX(-50%) translateY(-100%);font-size: 58px;font-family: Cambria, Cochin, Georgia, Times, 'Times New Roman', serif;border: 2px solid #fff;padding: 7.5px 15px;background: rgba(0, 0, 0, 0.5);border-radius: 3px;overflow: hidden;
}span.pen {position: relative;display: inline-block;animation: drop 0.75s;
}canvas {width: 100%;height: 100%;
}@keyframes drop {0% {transform: translateY(-100px);opacity: 0;}90% {opacity: 1;transform: translateY(10px);}100% {transform: translateY(0px);}
}
)
EM算法的推导)
