/*position de menu et les suite*/
h1{
    color: black;
    height: 100px;/*元素的高度*/
    position: absolute;
    top: 18%;/*元素的顶部边界离父元素的的位置是父元素高度的一半*/
    margin-top: -50px;/*设置元素顶边负边距，大小为元素高度的一半*/
    left: 49%;/*配合margin-left的负值实现水平居中*/
    margin-left: -100px;
    border: none;
    font-weight:bold;
    font-size:70px;
    font-family: 'Avenir Next', 'Helvetica Neue', 'Lato', 'Helvetica', 'Arial', sans-serif;
}

#presentation{
    top: 30%;
}
#bao1{
    top: 40%;
  }
#bao2{
    top: 50%;
}
#bao3{
    top: 60%;
}
#bao4{
    top: 70%;
}
#analyse{
    top: 80%;

}

#presentation, #bao1, #bao2, #bao3, #bao4, #analyse{
      position: absolute;
      margin-top: -50px;/*设置元素顶边负边距，大小为元素高度的一半*/
      left: 45%;/*配合margin-left的负值实现水平居中*/
      margin-left: -100px;
      font-family: 'Avenir Next', 'Helvetica Neue', 'Lato', 'Helvetica', 'Arial', sans-serif;
}



* { margin: 0; padding: 0; }
html{ 
    background: url(../image/2.jpg) no-repeat center center fixed; 
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}

/* Demo Buttons Style */
.codrops-demos {
  padding-top: 2em;
  font-size: 35px;
  font-weight:normal;
}

.codrops-demos a {
  display: inline-block;
  margin: 0.5em;
  padding: 0.05em 0.1em;
  outline: none;
  border: 2px solid #fff;
  color: #fff;
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: 1px;
  font-weight: 600;
}

.codrops-demos a:hover,
.codrops-demos a.current-demo,
.codrops-demos a.current-demo:hover {
  border-color: #333;
  color: #FFFF00;
  border: 1.5px black;
  border-radius: 1px;
}