:root {
    --msir-primary: #2F5FA7;
    --msir-primary-strong: #1E3F73;
    --msir-primary-soft: #EEF3FA;
    --msir-primary-line: #D3DFEF;
    --msir-ink: #1F2A37;
    --msir-text: #3E4A59;
    --msir-muted: #6B7685;
    --msir-surface: #FFFFFF;
    --msir-bg-alt: #F6F8FB;
    --msir-study: #2F5FA7;
    --msir-published: #7A8593;
    --msir-public: #8A6D3B;
    --msir-danger: #B3261E;
    --msir-radius: 10px;
    --msir-shadow: 0 1px 2px rgba(16,24,40,.06), 0 4px 12px rgba(16,24,40,.06);
    --msir-page-bg: #F1F4F9;     /* 页面底色：浅灰蓝，衬托白色内容面板 */
    --msir-header-bg: linear-gradient(180deg, #EDF3FB 0%, #D6E3F3 100%);  /* 页头导航区底色 */
}

body, ul {
    margin: 0;
    padding: 0;
}
h1 {
    margin-top: 15px;
    margin-left: 30px;
    font-weight: bold;
    color: var(--msir-ink);

}
.page-container{
    display: flex;
    flex-direction: column;
    min-height: 85vh;
}
/* 正文放在白色面板里，和浅灰蓝的页面底色区分开 */
.extend-content{
    flex-grow: 1;
    margin: 24px 15% 32px;
    padding: 4px 32px 28px;
    background: var(--msir-surface);
    border: 1px solid var(--msir-primary-line);
    border-radius: 12px;
    box-shadow: var(--msir-shadow);
}
body {
    font-family: Arial, sans-serif;
    color: var(--msir-text);
    background: var(--msir-page-bg);
}
header {
    text-align: center;
    display: flex;
    background: var(--msir-header-bg);
    border-bottom: 1px solid var(--msir-primary-line);
    box-shadow: 0 2px 6px rgba(16,24,40,.06);
}

#logo img {
    margin: 10px 10px;
    height: 75px;
    mix-blend-mode: multiply;   /* logo 图片是白底，融进页头底色 */
}

#title img {
    margin: 5px 10px 0 -25px;
    height: 90px;
}
nav {
    width: 80%;
    height: 50px;
    background-color: transparent;
}

nav ul {
    list-style-type: none;
    padding: 0;
    display: flex;
    justify-content: center;
}

nav ul li a {
    padding: 40px 30px;
    text-decoration: none;
    color: var(--msir-ink);
    display: block;
    font-size: 20px;
    font-weight: bold;
}

nav ul li a:hover {
    color: var(--msir-primary);
    background: rgba(255,255,255,.75);
}


.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown::after {
    content: "▼";
    font-size: 10px;
    margin-left: 0;
    position: absolute;
    right: 15px;
    top: 51%;
    transform: translateY(-50%);
}

.dropdown-content {
    position: absolute;
    top: 100%;
    left: 0;
    opacity: 0;
    visibility: hidden;
    max-height: 0;
    overflow: auto;
    background-color: #fff;
    border: 1px solid var(--msir-primary-line);
    border-radius: 8px;
    min-width: 160px;
    box-shadow: var(--msir-shadow);
    z-index: 1;
    transition: opacity 0.7s ease, max-height 0.7s ease;
    transform: translateY(-5px);
}


.dropdown-content.show-dropdown {
    opacity: 1;
    visibility: visible;
    max-height: 300px;
}


.dropdown-content a {
    color: var(--msir-text);
    width: 230px;
    font-size: 15px;
    font-weight: normal;
    padding: 8px 16px;
    text-decoration: none;
    text-align: start;
    display: block;
}

.dropdownspecies {
    font-style: italic;
}

.dropdown-content a:hover {
    background-color: var(--msir-primary-soft);
    color: var(--msir-primary-strong);
}


.head-line {
    height: 4px;
    margin-bottom: 5px;
    background: var(--msir-primary-strong);
}

/* 页头已有下边线，正文上方的分隔线不再需要 */
.page-container > .head-line {
    display: none;
}


.foot-line {
    display: none;
    height: 0;
}

/* 页脚与页头呼应：同一组浅蓝渐变，方向相反（上深下浅），底部 4px 深蓝细条对应页面顶部的细条 */
footer {
    background: linear-gradient(180deg, #D6E3F3 0%, #EDF3FB 100%);
    border-top: 1px solid var(--msir-primary-line);
    border-bottom: 4px solid var(--msir-primary-strong);
    color: var(--msir-text);
    font-size: 14px;
    text-align: center;
    padding: 18px 0;
    position: relative;
    bottom: 0;
    width: 100%;
}

footer p {
    margin: 0;
    padding: 5px;
}

footer a {
    color: var(--msir-primary-strong);
    text-decoration: none;
}

footer a:hover {
    text-decoration: underline;
}