圣诞将至：js加html5教你写出动态旋转圣诞树。

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    <script>
      M = Math;
      Q = M.random; J = [];
      U = 16;
      T = M.sin;
      E = M.sqrt;
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        with (M[k] = k ? c.cloneNode(0) : c) {
          width = height = k ? 32 : W = 446;
          with (getContext('2d'))
          if (k > 10 | !k)
            for (
              font = '60px Impact',
              V = 'rgba('; I = i * U, fillStyle = k ? k == 13 ? V + '205,205,215,.15)' :
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            x = T(i),
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            D = x * x + y * y,
            B = E(D - x / .9 - 1.5 * y + 1),
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          return (
            m[2] - l[2]) * A + (l[0] - m[0]) * T(D);
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        J.sort(G);
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              ('Happy Christmas!', U, 345);
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              ((157 * (i * i) + T(D * 5 + i * i) * 5) % W) >> 0,
              ((113 * i + (D * i) / 60) % (290 + i / 99)) >> 0);
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