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<form action="index.html" class="login login--twitter" id="css-element">
  <h1>Twitter</h1>
  <input type="text" name="username" class="login-input" placeholder="Username">
  <input type="password" name="password" class="login-input" placeholder="Password">
  <input type="submit" value="Login" class="login-submit">
  <p class="login-help"><a href="index.html">Forgot password?</a></p>
</form>
<div class="mask"></div>
<svg height="0">
  <clippath id="clippath" clipPathUnits="objectBoundingBox">
    <rect x="0" y="0" width=".5" height="1"></rect>
  </clippath>
  <mask id="mask">
    <rect width="50%" height="500" fill="url(#gradient)"/>
    <linearGradient x1="0" y1="0" x2="1" y2="0" id="gradient">
      <stop offset="0%" stop-color="black" />
      <stop offset="50%" stop-color="white" />
    </linearGradient>
  </mask>
</svg>
  
<p class="info">Fold effect only supported by Firefox</p>
<p class="info"><a href="http://www.cssflow.com/snippets/facebook-login-form/demo">Login form design</a> by Thibaut Courouble</p>
@supports (background:-moz-element(#css-element)) {
  .login::after,
  .login::before {
    content: '';
    position: absolute;
    z-index: 3;
    top: -1px; bottom: -1px; left: -1px; right: 50%;
    pointer-events: none;
    background-image: -moz-element(#css-element);
    transform-origin: 100% 50%;
    transform: perspective(500px) rotateX(0deg) rotateY(0deg); 
    transition: transform .2s, filter .2s;
  }
  .login::after {
    left: 50%; right: -1px;
    transform-origin: 0 50%; 
    background-position: top right;
  }
  .login:hover::after,
  .login:hover::before {
    transition-timing-function: cubic-bezier(.2,1.8,.6,.7);
    transition-duration: .4s;
  }
  .login:hover::after {
    transform: perspective(500px) rotateY(45deg);
    filter: brightness(.6);
  }
  .login:hover::before {
    transform: perspective(500px) rotateY(-45deg);
  }

  .mask {
    position: absolute;
    z-index: 2;
    top: 0; bottom: 0; left: 0; right: 0;
    background: #222;
    pointer-events: none;
  }
}



/* cosmetics */
*,
*::before,
*::after {
  box-sizing: border-box;
}
body {
  font: 12px/20px 'Lucida Grande', Verdana, sans-serif;
  color: #404040;
  background: #222;
}

input, textarea, select, label {
  font-family: inherit;
  font-size: 12px;
}
.login {
  position: relative;
  margin: 50px auto 20px auto;
  padding: 18px 20px;
  width: 250px;
  background-color: #55acee;
  background-clip: padding-box;
  border: 1px solid #172b4e;
  border-bottom-color: #142647;
  border-radius: 5px;
  box-shadow: inset 0 1px rgba(255, 255, 255, 0.3), inset 0 0 1px 1px rgba(255, 255, 255, 0.1), 0 2px 10px rgba(0, 0, 0, 0.5);
}
.login > h1 {
  margin-bottom: 20px;
  font-size: 16px;
  font-weight: bold;
  color: white;
  text-align: center;
  text-shadow: 0 -1px rgba(0, 0, 0, 0.4);
}

.login-input {
  display: block;
  width: 100%;
  height: 37px;
  margin-bottom: 20px;
  padding: 0 9px;
  color: white;
  text-shadow: 0 1px black;
  background: rgba(0,0,0,.5);
  border: 1px solid #15243b;
  border-top-color: #0d1827;
  border-radius: 4px;
  background-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.35), rgba(0, 0, 0, 0.2) 20%, rgba(0, 0, 0, 0));
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.3), 0 1px rgba(255, 255, 255, 0.2);
}
.login-input:focus {
  outline: 0;
  background-color: rgba(0,0,0,.6);
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.3), 0 0 4px 1px rgba(255, 255, 255, 0.6);
}
.lt-ie9 .login-input {
  line-height: 35px;
}

.login-submit {
  display: block;
  width: 100%;
  height: 37px;
  margin-bottom: 15px;
  font-size: 14px;
  font-weight: bold;
  color: #294779;
  text-align: center;
  text-shadow: 0 1px rgba(255, 255, 255, 0.3);
  background: #adcbfa;
  background-clip: padding-box;
  border: 1px solid #284473;
  border-bottom-color: #223b66;
  border-radius: 4px;
  cursor: pointer;
  background-image: linear-gradient(to bottom, #d0e1fe, #96b8ed);
  box-shadow: inset 0 1px rgba(255, 255, 255, 0.5), inset 0 0 7px rgba(255, 255, 255, 0.4), 0 1px 1px rgba(0, 0, 0, 0.15);
}
.login-submit:active {
  background: #a4c2f3;
  box-shadow: inset 0 1px 5px rgba(0, 0, 0, 0.4), 0 1px rgba(255, 255, 255, 0.1);
}

.login-help {
  text-align: center;
}
.login-help > a {
  font-size: 11px;
  color: #fff;
  text-decoration: none;
  text-shadow: 0 -1px rgba(0, 0, 0, 0.4);
}
.login-help > a:hover {
  text-decoration: underline;
}
.info {
  position: relative;
  z-index: 2;
  text-align: center;
  color: rgba(255,255,255,.3);
}
.info a {
  color: inherit;
}
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