Modelo de calculadora HTML CSS


<!DOCTYPE html>
<html>
<head>
  <title></title>
  <style type="text/css">
    h1{
      text-align: center;
      margin-top: 0.67em;
      margin-bottom: 0.67em;
    }
    *{
      margin: 0;
      padding: 0;
    }
    .container{
      margin: auto;
      width: 25%;
      padding: 10px;
      border: 1px solid #f2f2f2;
      -webkit-box-shadow: 1px 1px 4px 0px rgba(176,176,176,1);
         -moz-box-shadow: 1px 1px 4px 0px rgba(176,176,176,1);
              box-shadow: 1px 1px 4px 0px rgba(176,176,176,1);
      background-color: #fff;
      height: 450px;
      background-color: #F8F8F8;
    }
    .header{
      background-color: #81C784;
      padding: 10px;
      color: #fff;
      text-align: center;
    }
    .result{
      font-size: 24px;
      padding: 24px 5px;
      font-weight: 700;
      text-align: right;
      width: 96%;
      border: none;
      background-color: #F8F8F8;
    }
    .first-row,
    .second-row,
    .third-row,
    .fourth-row,
    .conflict
    {
      display: inline-block;
      width: 100%;
    }
    .global{
     padding: 15px;
     font-weight: bold;
     font-size: 16px;
     border: none;
     border-radius: 3px;
     background-color: #F2F2F2;
     float: left;
     width: 23.5%;
     margin: 0 2px;
     /*border: 1px solid #000;*/
    }
    .conflict .left,
    .conflict .right{
      float: left;
      position: relative;
    }
    .left{
      width: 74%;
    }
    .right{
      width: 24%;
    }
    .big{
      padding: 15px;
      font-weight: bold;
      font-size: 16px;
      border: none;
      border-radius: 3px;
      background-color: #F2F2F2;
      float: left;
      width: 64.5%;
      margin: 0 2px;
    }
    .small{
      padding: 15px;
      font-weight: bold;
      font-size: 16px;
      border: none;
      border-radius: 3px;
      background-color: #F2F2F2;
      float: left;
      width: 31.5%;
      margin: 0 2px;
    }
    .plus{
      height: 105px;
      width: 100%;
    }
    .green{
      background-color: #81C784;
    }
    .red{
      background-color: #F50258
    }
    .grey{
      background-color: #F2F2F2;
    }
    .white-text{
      color: #fff;
    }
    .top-margin{
      margin-top: 4px;
    }

  </style>
</head>
<body>

  <h1>Calculator Design Using HTML Layout</h1>
  <div class="container">
    <div class="header">Calculator</div>
    <input type="text" class="result">
    <div class="first-row">
      <input type="button" name="" value="&radic;" class="global">
      <input type="button" name="" value="(" class="global">
      <input type="button" name="" value=")" class="global">
      <input type="button" name="" value="%" class="global">
    </div>
    <div class="second-row">
      <input type="button" name="" value="7" class="global">
      <input type="button" name="" value="8" class="global">
      <input type="button" name="" value="9" class="global">
      <input type="button" name="" value="/" class="global">
    </div>
    <div class="third-row">
      <input type="button" name="" value="4" class="global">
      <input type="button" name="" value="5" class="global">
      <input type="button" name="" value="6" class="global">
      <input type="button" name="" value="X" class="global">
    </div>
    <div class="fourth-row">
      <input type="button" name="" value="1" class="global">
      <input type="button" name="" value="2" class="global">
      <input type="button" name="" value="3" class="global">
      <input type="button" name="" value="-" class="global">
    </div>
    <div class="conflict">
      <div class="left">
        <input type="button" name="" value="0" class=" big">
        <input type="button" name="" value="." class=" small">
        <input type="button" name="" value="Del" class=" red small white-text top-margin">
        <input type="button" name="" value="=" class=" green white-text big top-margin">
      </div>
      <div class="right">
        <input type="button" name="" value="+" class="global grey plus">
      </div>
    </div>
  </div>
</body>
</html>
adens