css fixed窗口底部固定定位

前言已经不想说了，直接贴代码吧

<div class="btn_box box1" id="box1"><button class="btn_confirm" id="btn_confirm">确认</button></div>

.btn_box {width: 100%;position: fixed;display: flex;align-items: center;}.box1 {bottom: 6.80rem;}.btn_confirm {width: 19.69rem;height: 3.06rem;background: #cccccc;border-radius: 0.31rem;font-size: 0.94rem;font-family: PingFangSC-Medium, PingFang SC;color: #FFFFFF;margin: 0 auto;}