* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: url(bg.jpg) no-repeat center;
    background-size: cover;
    //把背景图像扩展至足够大，以使背景图像完全覆盖背景区域。背景图像的某些部分也许无法显示在背景定位区域中。
}

.contact-page {
    width: 100%;
    max-width: 1400px;
    padding: 25px;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    flex-wrap: wrap;
}

h2 {
    width: 100%;
    margin-bottom: 80px;
    text-transform: uppercase;
    font-size: 40px;
}

.contact-info,
.contact-form {
    flex: 1;
}

.item {
    margin-bottom: 40px;
    font-size: 16px;
}

.item .icon {
    width: 40px;
    height: 40px;
    line-height: 40px;
    text-align: center;
    background-color: skyblue;
    color: #fff;
    border-radius: 50%;
    margin-right: 5px;
}

.contact-form {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

.textb {
    width: calc(50% - 10px);
    /* 每一个textb盒子的宽度始终保持父盒子宽度一半减去10px */
    height: 40px;
    background-color: black;
    border: none;
    color: #fff;
    padding: 20px;
    margin-bottom: 20px;
}

textarea {
    width: 100%;
    min-height: 200px;
    max-height: 400px;
    resize: vertical;
    //用户可调整元素的高度。
    background-color: black;
    border: none;
    color: #fff;
    padding: 20px;
    margin-bottom: 20px;
}

.btn {
    margin-left: auto;
    width: 120px;
    height: 40px;
    text-transform: uppercase;
    background-color: skyblue;
    border: none;
    border: 2px solid skyblue;
    transition: 0.3s linear;
    cursor: pointer;
}

.btn:hover {
    background-color: transparent;
    color: skyblue;
}

@media screen and (max-width:800px) {
    .contact-page {
        max-width: 800px;
    }
    h2 {
        font-size: 40px;
        margin-bottom: 40px;
    }
    .contact-info,
    .contact-form {
        flex: 100%
    }
    .textb {
        width: 100%;
    }
}