纯CSS打造25.60秒精准计时器

创建25.60秒计时器：HTML与CSS实现

使用HTML和CSS构建精确到百分之一秒的计时器，无需JavaScript。以下方法结合CSS动画和SVG路径动画实现。

HTML结构

<div class="timer-container">
  <svg class="timer-svg" viewBox="0 0 100 100">
    <circle class="timer-base" cx="50" cy="50" r="45"/>
    <path class="timer-progress" d="M50,5 A45,45 0 0 1 95,50"/>
  </svg>
  <div class="timer-display">25.60</div>
</div>

CSS动画实现

.timer-container {
  position: relative;
  width: 200px;
  height: 200px;
}

.timer-svg {
  transform: rotate(-90deg);
}

.timer-base {
  fill: none;
  stroke: #eee;
  stroke-width: 5;
}

.timer-progress {
  fill: none;
  stroke: #4CAF50;
  stroke-width: 5;
  stroke-linecap: round;
  animation: countdown 25.6s linear forwards;
}

.timer-display {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-family: monospace;
  font-size: 2rem;
}

@keyframes countdown {
  to {
    stroke-dashoffset: 0;
  }
}

SVG路径动画原理

通过CSS控制SVG路径的stroke-dasharray和stroke-dashoffset属性创建动画效果：

stroke-dasharray定义虚线模式
stroke-dashoffset控制虚线起始位置

计算周长公式： [ 周长 = 2 \times \pi \times r = 2 \times \pi \times 45 \approx 282.74 ]

初始设置：

.timer-progress {
  stroke-dasharray: 282.74;
  stroke-dashoffset: 282.74;
}

精确控制时间

调整动画持续时间与显示数字同步：

总动画时间设为25.6秒
使用linear计时函数保持匀速
forwards保持动画结束状态

显示更新可通过CSS计数器实现：

.timer-container {
  counter-reset: time 2560;
}

.timer-display::before {
  content: counter(time);
  animation: count 25.6s steps(2560) forwards;
}

@keyframes count {
  to {
    counter-increment: time -2560;
  }
}

响应式设计改进

添加媒体查询适应不同屏幕：

@media (max-width: 600px) {
  .timer-container {
    width: 150px;
    height: 150px;
  }
  .timer-display {
    font-size: 1.5rem;
  }
}

视觉增强技巧

添加发光效果和过渡：

.timer-progress {
  filter: drop-shadow(0 0 2px rgba(76, 175, 80, 0.7));
  transition: stroke 0.3s ease;
}

通过组合CSS动画、SVG路径绘制和计数器功能，可以创建纯前端实现的精确计时器。这种方法适用于需要轻量级、无JavaScript的计时场景，如演示页面或性能敏感环境。

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