:root {
    --bg-color: #ffffff;
    --text-color: #1a1a1a;
    --link-color: #2563eb;
    --link-hover-color: #1d4ed8;
    --header-bg: #f8fafc;
    --card-bg: #ffffff;
    --card-shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --border-color: #e2e8f0;
    --accent-color: #10b981;
    --audio-image-filter: invert(0%)
}

[data-theme="dark"] {
    --bg-color: #111827;
    --text-color: #f9fafb;
    --link-color: #60a5fa;
    --link-hover-color: #93c5fd;
    --header-bg: #1f2937;
    --card-bg: #1f2937;
    --card-shadow: 0 10px 15px -3px rgb(0 0 0 / 0.5);
    --border-color: #374151;
    --accent-color: #34d399;
    --audio-image-filter: invert(100%)
}

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

body {
    font-family: "微軟正黑體", Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 1.8rem;
}

header {
    background-color: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 2rem;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.header-content>h1 {
    font-size: 1.5rem;
    font-weight: 700;
}

.header-content>h1>a{
    color: inherit;
    text-decoration: none;
}

.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    color: var(--text-color);
    cursor: pointer;
    font-size: 0.875rem;
    transition: all 0.2s;
}

.theme-toggle:hover {
    background-color: var(--border-color);
}

.hero {
    margin-bottom: 3rem;
}

.hero p {
    font-size: 1.25rem;
    opacity: 0.8;
}

.grade-section {
    margin-bottom: 2rem;
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 0.75rem;
    padding: 1.5rem;
    box-shadow: var(--card-shadow);
}

.grade-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--accent-color);
    border-left: 4px solid var(--accent-color);
    padding-left: 1rem;
}

.lesson-list {
    font-size: 1.2rem;
    list-style: none;
    display: grid;
    grid-template: auto / 1fr 1fr;
}

.lesson-item {
    margin-bottom: 0.5rem;
}

.lesson-link {
    text-decoration: none;
    color: var(--link-color);
    font-weight: 500;
    transition: color 0.2s;
    display: block;
    padding: 0.5rem;
    border-radius: 0.25rem;
}

.lesson-link:hover {
    color: var(--link-hover-color);
    background-color: rgba(37, 99, 235, 0.05);
}

[data-theme="dark"] .lesson-link:hover {
    background-color: rgba(96, 165, 250, 0.1);
}

footer {
    margin-top: 4rem;
    text-align: center;
    font-size: 0.875rem;
    opacity: 0.6;
    padding-bottom: 2rem;
}

/* Lesson Page Styles */
.site-logo {
    text-decoration: none;
    color: inherit;
}

.lesson-page-title {
    font-size: 1.3rem;
    margin-bottom: 2rem;
    text-align: center;
    color: var(--accent-color);
}

.card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 0.75rem;
    padding: 2rem;
    box-shadow: var(--card-shadow);
}

.content-block h3 {
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    opacity: 0.6;
    margin-bottom: 1rem;
}

.content-block{
    font-size: 1.2rem;
    line-height: 1.5;
}

.audio{
    text-align: right;
}

.audio>img{
    cursor:pointer;
    margin-left:10px;
    filter:var(--audio-image-filter);
}
.audio>audio{
    visibility: hidden;
}

.content-block p{
    white-space:pre-wrap;
    margin-bottom:15px;
}

.separator {
    border: 0;
    border-top: 1px solid var(--border-color);
    margin: 2rem 0;
}

.navigation-footer {
    margin-top: 2rem;
    text-align: center;
}

.back-link {
    font-size: 1.2rem;
    text-decoration: none;
    color: var(--link-color);
    font-weight: 500;
    transition: color 0.2s;
}

.back-link:hover {
    color: var(--link-hover-color);
}