:root {
    --text-base: 15px;
    --text-large: 1.5rem;
    --line-height: 1.5;
    --bg-color: #fafafa;
    --text-color: #222;
    --header-bg: #0070f3;
    --header-text: white;
    --main-bg: white;
    --main-shadow: rgba(0, 0, 0, 0.05);
    --link-color: #0070f3;
    --footer-color: #666;
    --lang-menu-bg: white;
    --lang-menu-text: #222;
    --lang-menu-hover: #f5f5f5;
    --lang-menu-shadow: rgba(0, 0, 0, 0.15);
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #1a1a1a;
        --text-color: #e4e4e4;
        --header-bg: #0052b3;
        --header-text: #e4e4e4;
        --main-bg: #2a2a2a;
        --main-shadow: rgba(0, 0, 0, 0.3);
        --link-color: #4a9eff;
        --footer-color: #a0a0a0;
        --lang-menu-bg: #2a2a2a;
        --lang-menu-text: #e4e4e4;
        --lang-menu-hover: #3a3a3a;
        --lang-menu-shadow: rgba(0, 0, 0, 0.5);
    }
}

@media (min-width: 1024px) {
    :root {
        --text-base: 14.5px;
        --line-height: 1.55;
    }
}

body {
    font-family:
        -apple-system, BlinkMacSystemFont, "Helvetica Neue", "Segoe UI", Roboto,
        "PingFang SC", "Hiragino Sans GB", "Noto Sans CJK SC",
        "Microsoft YaHei", sans-serif;
    font-size: var(--text-base);
    line-height: var(--line-height);
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 0;
    text-rendering: optimizeLegibility;
    -webkit-font-smoothing: antialiased;
}

header {
    background-color: var(--header-bg);
    color: var(--header-text);
    padding: 1.8rem 1rem;
    text-align: center;
    position: relative;
}

header h1 {
    font-size: var(--text-large);
    margin-bottom: 0.3rem;
}

header p {
    margin: 0.2rem 0 0;
    font-size: 0.95rem;
    opacity: 0.9;
}

main {
    max-width: 800px;
    margin: 2rem auto;
    padding: 1.8rem 1.5rem;
    background: var(--main-bg);
    border-radius: 12px;
    box-shadow: 0 2px 8px var(--main-shadow);
}

h2 {
    color: var(--link-color);
    font-size: 1.15rem;
    margin-top: 1.6rem;
    margin-bottom: 0.6rem;
}

p {
    margin: 0.4rem 0 0.8rem;
    font-size: 0.97rem;
}

ul {
    margin: 0.4rem 0 1rem 1.2rem;
    padding: 0;
}
ul li {
    margin-bottom: 0.3rem;
    font-size: 0.95rem;
}

a {
    color: var(--link-color);
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}

footer {
    text-align: center;
    font-size: 0.9rem;
    color: var(--footer-color);
    margin: 2rem 0 3rem;
}

.lang-switch-container {
    position: absolute;
    right: 1rem;
    top: 1rem;
}

.lang-switch {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: none;
    padding: 0.35rem 0.75rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    transition: background 0.2s ease;
}
.lang-switch:hover {
    background: rgba(255, 255, 255, 0.35);
}

.lang-menu {
    display: none;
    position: absolute;
    right: 0;
    top: 100%;
    margin-top: 0.5rem;
    background: var(--lang-menu-bg);
    border-radius: 6px;
    box-shadow: 0 4px 12px var(--lang-menu-shadow);
    min-width: 120px;
    overflow: hidden;
    z-index: 1000;
}

.lang-option {
    display: block;
    width: 100%;
    padding: 0.6rem 1rem;
    border: none;
    background: var(--lang-menu-bg);
    color: var(--lang-menu-text);
    text-align: left;
    cursor: pointer;
    font-size: 0.85rem;
    transition: background 0.2s ease;
}

.lang-option:hover {
    background: var(--lang-menu-hover);
}

@media (max-width: 600px) {
    header {
        padding: 1.5rem 1rem;
    }
    main {
        margin: 1rem;
        padding: 1.2rem 1rem;
    }
    h1 {
        font-size: 1.3rem;
    }
    h2 {
        font-size: 1.05rem;
    }
}