@import url('https://fonts.googleapis.com/css?family=Muli&display=swap');

* {
    box-sizing: border-box;
}

body {
    font-family: 'Muli', sans-serif;
    background-color: rgb(236, 236, 236);
    height: 95vh;
}

#title {
    text-align: center;
    padding-top: 5vh;
}

.container {
    width: 100%;
    /* 子元素按列排，水平居中 */
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* =====默认样式===== */
.box {
    width: 600px;
    height: 100%;
    position: relative;     /* 提供给button定位 */

    background-color: #fff;
    border-radius: 10px;
    padding: 10px 30px;
    margin: 10px 0;

    /* 子元素按列排 */
    display: flex;
    flex-direction: column;

    transition: box-shadow 0.3s ease-out;
}

.btn {
    /* 定位 */
    position: absolute;
    right: 20px;
    top: 35px;

    border: 0;
    background-color: inherit;
    cursor: pointer;
}

.fa-times {
    /* 隐藏图标X */
    display: none;
}

.text {
    display: none;
}

.title {
    color: #343a40;
    width: 95%;
}

/* =====激活样式===== */
.box.active {
    box-shadow: 0 0 8px 0 rgba(0,0,0,0.1);
    transition: box-shadow 0.3s ease-out;
}

.box.active .text {
    display: inline;
}

.box.active .fa-times {
    display: inline;
}

.box.active .fa-chevron-down {
    display: none;
}