tongtongkuaikuai/* --- 基础与字体设置 --- */
body {
    font-family: 'Noto Serif SC', serif;
    transition: background-color 0.5s, color 0.5s;
}

/* --- CSS 变量定义 --- */
:root {
    /* 默认主题：翡翠绿 */
    --bg-color: #f0f5f1;
    --text-color: #1a3a3a;
    --primary-color: #6a9c89;
    --card-bg-color: #d1e2d8;
    --card-alt-bg-color: #e3f0e9;
    --separator-color: #c1d1c8;
    --card-border-color: transparent;
}

body.theme-jade {
    --bg-color: #f0f5f1;
    --text-color: #1a3a3a;
    --primary-color: #6a9c89;
    --card-bg-color: #d1e2d8;
    --card-alt-bg-color: #e3f0e9;
    --separator-color: #c1d1c8;
    --card-border-color: transparent;
}

body.theme-imperial {
    --bg-color: #fdfaf2;
    --text-color: #0d1b2a;
    --primary-color: #e6b800;
    --card-bg-color: #fff8dc;
    --card-alt-bg-color: #fffbe9;
    --separator-color: #e6dca9;
    --card-border-color: transparent;
}

body.theme-crimson {
    --bg-color: #fff8f1;
    --text-color: #5c1a1b;
    --primary-color: #b94547;
    --card-bg-color: #faebd7;
    --card-alt-bg-color: #fcf3e8;
    --separator-color: #e8d7c7;
    --card-border-color: transparent;
}

body.theme-parchment {
    --bg-color: #f5eeda;
    --text-color: #4e342e;
    --primary-color: #4e342e;
    --card-bg-color: #fffbf0;
    --card-alt-bg-color: #fdf8ec;
    --separator-color: #dcd1b8;
    --card-border-color: #dcd1b8;
}

/* --- 通用样式 --- */
body {
    background-color: var(--bg-color);
    color: var(--text-color);
}

.header-decoration {
    border-color: var(--primary-color);
}

.day {
    color: var(--primary-color);
}

.separator {
    border-color: var(--separator-color);
}

/* --- 卡片样式 --- */
.static-card {
    background-color: var(--card-bg-color);
    color: var(--text-color);
    border: 1px solid var(--card-border-color);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    transition: box-shadow 0.3s ease, border-color 0.3s ease;
}

section.static-card:nth-of-type(odd) {
    background-color: var(--card-alt-bg-color);
}

.static-card:hover {
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    border-color: var(--primary-color);
}

/* --- 卡片入场动画 --- */
.static-card {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.static-card.is-visible {
    opacity: 1;
    transform: translateY(0);
}

/* 段落首行缩进 */
.static-card p {
    text-indent: 2em;
}

/* --- 主题切换按钮 --- */
.theme-button {
    transition: all 0.2s ease;
    border: 2px solid transparent;
}

.theme-button.active {
    transform: scale(1.1);
    border-color: var(--primary-color);
}

/* --- 视频容器 --- */
.video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    height: 0;
    overflow: hidden;
    max-width: 100%;
    background: #000;
    margin-bottom: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

/* --- 作业标题下划线动画 --- */
@keyframes slide-bg {
    0% { background-position: 200% 0; }
    100% { background-position: -200% 0; }
}

.animated-underline {
    position: relative;
    display: inline-block;
}

.animated-underline::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 100%;
    height: 4px;
    background-image: linear-gradient(90deg, var(--primary-color), var(--card-alt-bg-color), var(--primary-color));
    background-size: 300% 100%;
    animation: slide-bg 5s linear infinite;
    border-radius: 2px;
}