水平垂直居中

.container {
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    text-align: center;
    height: 400px;
    line-height: 400px;
}

.parent {
    text-align: center;
    height: 400px;
    line-height: 400px;
}
.child {
    display: inline-block;
}


/*   多行文本垂直居中方法一   */
.container {
    display: table-cell;
    vertical-align: middle;
    height: 400px;
}


/*   多行文本垂直居中方法二   */
.parent {
    height: 400px;
    line-height: 400px;
}
.child {
    display: inline-block;
    vertical-align: middle;
    line-height: 1.5;
}

/*   方法一：absolute + 负值margin   */
.parent {
    position: relative;
    height: 400px;
}
.child {
    position: absolute;
    left: 50%;
    margin-left: -200px;
    width: 400px;
    top: 50%;
    margin-top: -100px;
    height: 200px;
}


/*   方法二：absolute + margin auto   */
.parent {
    position: relative;
    height: 400px;
}

.child {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    margin: auto;
    width: 50%;
    height: 50%;
}


/*   方法三：absolute + calc   */
.parent {
    position: relative;
    height: 400px;
}

.child {
    position: absolute;
    left: calc(50% - 200px);
    width: 400px;
    top: calc(50% - 100px);
    height: 200px;
}

.parent {
    position: relative;
}

.child {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    /*   水平居中 left: 50%;transform: translate(-50%, 0);   */
}

.parent {
    display: table-cell;
    text-align: center;
    vertical-align: middle;
}

.child {
    display: inline-block;
}

.parent {
  display: grid;
  place-content: center;
  gap: 1ch;
}