利用table實現頁面實現移動端頁面自適應表單

爲了實現如圖所示的效果：

設置table的寬度爲百分比的值，讓其寬度隨頁面的寬度而改變。input佔據整個td的寬度。
主要html代碼以下：

<form action="">
    <table class="form">
        <tr>
            <td colspan="3"><input type="text" placeholder="姓名" name="username" id="user"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3"><input type="text" placeholder="公司名稱" name="company" id="company"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3"><input type="text" placeholder="國家/地區" name="area" id="area"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3"><input type="phone" placeholder="手機" name="phone" id="phone"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3"><input type="email" placeholder="電子郵箱" name="email" id="email"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3"><input type="text" placeholder="確認郵箱" name="email-c" id="email-c"/><span></span></td>
        </tr>
        <tr>
            <td class="r-box pl8" width="37%">是否開具發票</td><td class="r-box" width="21.9%"><label for="bill_y" class="r-label checked"><input type="radio" name="bill" id="bill_y"/>是</label></td><td class="r-box"><label for="bill_n" class="r-label"><input type="radio" name="bill" id="bill_n"/>否</label></td></td>
        </tr>
        <tr>
            <td colspan="3"><input type="text" placeholder="擡頭"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3" class="pb6"><input type="text" placeholder="聯繫地址"/><span></span></td>
        </tr>
        <tr>
            <td colspan="3"><input type="submit" value="繼續"/></td>
        </tr>
    </table>
</form>

主要的scss樣式以下：

.form{
  width: 96%;
  margin: 0.3rem auto;
  font-size: 0.7rem;
  td{
    height: 2.5rem;
  }
  input{
    font-family: "Microsoft Yahei";
    outline: none;
    color: #d8d8d8;
  }
  input[type=text],input[type=phone],input[type=email]{
    border: 1px solid #e10000;
    height: 1.55rem;
    line-height: 1.55rem;
    padding-left: 0.4rem;
    width: 100%;
    box-sizing: border-box;
    background: transparent;
  }