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  <title>SVG - 红绿灯</title>
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    <circle cx="70" cy="160" r="30" fill="yellow">
      <animate attributeName="opacity" values="1;0;0;1" dur="3s" repeatCount="indefinite" begin="1s" />
    </circle>

    <circle cx="70" cy="240" r="30" fill="#40CC40">
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