:root {
    --color-primary: #2A87D9;
}


.main-section {
    width: var(--center-width);
    margin: 0 auto;
}

body {
    gap: 1rem;
    background-color: #F5F5F5;
}

/*桌面端*/
@media (min-width: 999px) {
    :root {
        --center-width: 100rem
    }

    .mobile-menu {
        display: none;
    }

    .desktop-menu {
        display: flex;
    }
}

/*移动端*/
@media (max-width: 1000px) {
    :root {
        --center-width: calc(100% - 2rem);
    }

    header > h1 {
        display: none !important;
    }

    .mobile-menu {
        display: flex;
    }

    .desktop-menu {
        display: none;
    }
}

header {
    width: 100%;
    position: fixed;
    z-index: 999;
    background: url("../image/header-background.jpg") 100% no-repeat;
    background-size: cover;
    box-shadow: 0 .5rem .9rem 0 rgba(0, 0, 0, 0.07);
}

header>section{
    height: 5rem;
}
.desktop-menu {
    align-items: center;
}

.mobile-menu {
    padding: 0 1rem;
    gap: 1rem;
    align-items: center;
}

.desktop-menu > a {
    font-size: 1.4rem;
    font-weight: bold;
}

.desktop-menu > .select {
    border-bottom: .2rem solid var(--color-primary);
    color: var(--color-primary);
}

.mobile-menu > h1 {
    width: calc(100% - 1.5rem);
    text-align: start;
    font-size: 1.4rem;
    font-weight: bold;
}

.mobile-menu > button {
    border: none;
    cursor: pointer;
}

/*蒙层*/
.mobile-mask {
    position: fixed;
    top: 0;
    left: 0;
    z-index: 9;
}

.mobile-mask-menu {
    width: 100vw;
    height: 100vh;
}

/*空白部分*/
.mobile-mask-blank {
    width: calc(100% - 25rem);
    background-color: #141414;
    opacity: .5;
}

/*菜单*/
.mobile-mask-menu-nav {
    padding: 0 2rem;
    width: 25rem;
    height: 100%;
    background-color: #ffffff;
}

.mobile-mask-menu-nav > a {
    padding: 2rem 0;
    border-bottom: .1rem solid #eee;
}

.mobile-mask-menu-nav > .select {
    color: var(--color-primary);
}

h1 {
    text-align: center;
    font-weight: bold;
}

h2 {
    font-size: 2rem;
    font-weight: bold;
}

p {
    text-align: justify;
    white-space: pre-wrap;
}


main {
    margin-top: 6rem;
    flex: 1;
}


/*菜单-开始*/
.center {
    width: var(--center-width);
    margin: 0 auto;
}


footer {
    text-align: center;
    padding: 2.5rem 0;
    color: #FFFFFF;
    background-color: var(--color-primary);
}


.teacher-section {
    padding: 1.5rem 3rem;
    border-radius: .7rem;
    background: url("../image/101.png") 100% no-repeat;
    background-size: cover;
}

.teacher-section > p {
    color: var(--color-primary);
    gap: .5rem;
}

.submission-section {
    gap: 1rem;
}

.submission-section > h2 {
    color: var(--color-primary);
}

.submission-section > h3 {
    font: 1.4rem SourceHanSansCN-Bold;
}