Code:

<div class="center">
    <h1>HTML CSS, JavaScript 计算器</h1>
    <a href="https://github.com/guuibayer/simple-calculator" target="_blank"><i class="fa fa-github"></i></a>
    <form name="calculator">
        <input type="button" id="clear" class="btn other" value="C">
        <input type="text" id="display">
        <br>
        <input type="button" class="btn number" value="7" onclick="get(this.value);">
        <input type="button" class="btn number" value="8" onclick="get(this.value);">
        <input type="button" class="btn number" value="9" onclick="get(this.value);">
        <input type="button" class="btn operator" value="+" onclick="get(this.value);">
        <br>
        <input type="button" class="btn number" value="4" onclick="get(this.value);">
        <input type="button" class="btn number" value="5" onclick="get(this.value);">
        <input type="button" class="btn number" value="6" onclick="get(this.value);">
        <input type="button" class="btn operator" value="*" onclick="get(this.value);">
        <br>
        <input type="button" class="btn number" value="1" onclick="get(this.value);">
        <input type="button" class="btn number" value="2" onclick="get(this.value);">
        <input type="button" class="btn number" value="3" onclick="get(this.value);">
        <input type="button" class="btn operator" value="-" onclick="get(this.value);">
        <br>
        <input type="button" class="btn number" value="0" onclick="get(this.value);">
        <input type="button" class="btn operator" value="." onclick="get(this.value);">
        <input type="button" class="btn operator" value="/" onclick="get(this.value);">
        <input type="button" class="btn other" value="=" onclick="calculates();">
    </form>
</div>
<style>
    /* Basic Reset */
    * {
    	border: none;
    	font-family: 'Open Sans', sans-serif;
    	margin: 0;
    	padding: 0;
    }
    body {
    
    }
    .center {
    	background-color: #fff;
    	border-radius: 50%;
    	height: 600px;
    	margin: auto;
    	width: 600px;
    }
    h1 {
    	color: #495678;
    	font-size: 30px;	
    	margin-top: 20px;
    	padding-top: 50px;
    	display: block;
    	text-align: center;
    	text-decoration: none;
    }
    a {
    	color: #495678;
    	font-size: 30px;	
    	display: block;
    	text-align: center;
    	text-decoration: none;
    	padding-top: 20px;
    }
    form {
    	background-color: #495678;
    	box-shadow: 4px 4px #3d4a65;
    	margin: 40px auto;
    	padding: 40px 0 30px 40px;	
    	width: 280px;
    }
    .btn {
    	outline: none;
    	cursor: pointer;
    	font-size: 20px;
    	height: 45px;
    	margin: 5px 0 5px 10px;
    	width: 45px;
    }
    .btn:first-child {
    	margin: 5px 0 5px 10px;
    }
    .btn, #display, form {
    	border-radius: 25px;
    }
    #display {
    	outline: none;
    	background-color: #98d1dc;
    	box-shadow: inset 6px 6px 0px #3facc0;
    	color: #dededc;
    	font-size: 20px;
    	height: 47px;
    	text-align: right;
    	width: 165px;
    	padding-right: 10px;
    	margin-left: 10px;
    }
    .number {
    	background-color: #72778b;
    	box-shadow: 0 5px #5f6680;
    	color: #dededc;
    }
    .number:active {
    	box-shadow: 0 2px #5f6680;
      	-webkit-transform: translateY(2px);
      	-ms-transform: translateY(2px);
      	-moz-tranform: translateY(2px);
      	transform: translateY(2px);
    }
    .operator {
    	background-color: #dededc;
    	box-shadow: 0 5px #bebebe;
    	color: #72778b;
    }
    .operator:active {
    	box-shadow: 0 2px #bebebe;
      	-webkit-transform: translateY(2px);
      	-ms-transform: translateY(2px);
      	-moz-tranform: translateY(2px);
      	transform: translateY(2px);
    }
    .other {
    	background-color: #e3844c;
    	box-shadow: 0 5px #e76a3d;
    	color: #dededc;
    }
    .other:active {
    	box-shadow: 0 2px #e76a3d;
      	-webkit-transform: translateY(2px);
      	-ms-transform: translateY(2px);
      	-moz-tranform: translateY(2px);
      	transform: translateY(2px);
    }
</style>

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