@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: 800px;
    height: 300px;

    /* 水平居中 */
    margin-left: auto;
    margin-right: auto;

    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 0 8px 0 rgba(0,0,0,0.1);

    /* 子元素按列排，水平居中 */
    display: flex;
    flex-direction: column;
    align-items: center;
}

.container h2 {
    margin-top: 30px;
    letter-spacing: 2px;
    color: #868e96;
}

.text {
    font-weight: bold;
    font-size: 1.5rem;
    height: 40%;
    width: 80%;

    /* 子元素水平垂直居中 */
    display: flex;
    align-items: center;
    justify-content: center;
}

#btn {
    border: 0;
    border-radius: 5px;
    cursor: pointer;
    color: #fff;
    background-color: #339af0;
    padding: 15px 30px;
    margin-top: 20px;
    font-family: inherit;
    font-weight: bold;
    font-size: 1rem;
    box-shadow: 0 2px 8px 2px rgba(0,0,0,0.15);
}
#btn:active {
    transform: scale(0.98);
}