不确定行数的多行文本垂直水平居中的css

ul li {
            position:relative;
            display: table;
            width:3rem;
            height:3rem;
            background:url('image/defaultBg.jpg') 0 0/100% 100% no-repeat; float:left;
            margin-bottom:0.2rem;
            text-align:center;
            box-shadow: 0 0 0.2rem #888;
            transition: all 0.3s linear;
            transform-origin: 0 0;
            transform-style: preserve-3d;
            color:#b21e23;
            font-weight:bold;font-size: 18px;
            border:1px solid #b21e23;
            overflow: hidden;
        }
li .selects_item{
            position:absolute;
            top:50%;
            left:50%;
            display:table-cell;
            vertical-align:middle;
            height:1.3rem;
        }
lit .selects_item p{
            position:relative;
            top:-50%;
            left:-50%;
            width:3rem;
            margin:0 auto;
        }

<div>
        <ul>
            <li>
                <div class="selects_item">
                     <p>我是多行文本</p>
                     <p>我不确定行数，单行或多行</p>
                </div>
            </li>
        </ul>
    </div>