/* ===== 全局样式 ===== */
:root {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --bg-card: rgba(33, 38, 45, 0.6);
    --text-primary: #e6edf3;
    --text-secondary: #8b949e;
    --text-muted: #6e7681;
    --accent: #4f9cf9;
    --accent-hover: #388bfd;
    --accent-glow: rgba(79, 156, 249, 0.15);
    --green: #3fb950;
    --red: #f85149;
    --yellow: #d29922;
    --border: rgba(110, 118, 129, 0.2);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.section {
    padding: 80px 0;
}

.section-title {
    font-size: 32px;
    font-weight: 700;
    text-align: center;
    margin-bottom: 48px;
    letter-spacing: -0.5px;
}

/* ===== 导航栏 ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    transition: var(--transition);
    backdrop-filter: blur(12px);
    background: rgba(13, 17, 23, 0.7);
    border-bottom: 1px solid transparent;
}

.navbar.scrolled {
    background: rgba(13, 17, 23, 0.95);
    border-bottom: 1px solid var(--border);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 600;
    font-size: 18px;
}

.nav-logo-icon {
    width: 28px;
    height: 28px;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 28px;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 15px;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav-link:hover {
    color: var(--text-primary);
}

.nav-link.active {
    color: var(--accent);
}

.nav-btn {
    background: var(--accent);
    color: #fff !important;
    padding: 8px 20px;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.nav-btn:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 22px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: var(--transition);
}

/* ===== 按钮 ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-weight: 600;
    text-decoration: none;
    border: none;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.btn-primary {
    background: var(--accent);
    color: #fff;
}

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px var(--accent-glow);
}

.btn-outline {
    background: transparent;
    color: var(--text-primary);
    border: 1px solid var(--border);
}

.btn-outline:hover {
    border-color: var(--accent);
    color: var(--accent);
}

.btn-lg {
    padding: 14px 32px;
    font-size: 16px;
}

.btn-block {
    width: 100%;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* ===== 页脚 ===== */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border);
    padding: 48px 0 24px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 32px;
}

.footer-col h4 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 16px;
}

.footer-col p {
    color: var(--text-secondary);
    font-size: 14px;
}

.footer-col a {
    display: block;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 14px;
    padding: 4px 0;
    transition: var(--transition);
}

.footer-col a:hover {
    color: var(--accent);
}

.footer-bottom {
    border-top: 1px solid var(--border);
    padding-top: 24px;
    text-align: center;
}

.footer-bottom p {
    color: var(--text-muted);
    font-size: 13px;
}

/* ===== 表单 ===== */
.form-group {
    margin-bottom: 20px;
}

.form-label {
    display: block;
    font-size: 14px;
    font-weight: 500;
    margin-bottom: 8px;
    color: var(--text-secondary);
}

.form-input {
    width: 100%;
    padding: 12px 16px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-size: 15px;
    font-family: inherit;
    transition: var(--transition);
}

.form-input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.form-input::placeholder {
    color: var(--text-muted);
}

/* ===== 提示消息 ===== */
.alert {
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    margin-bottom: 16px;
}

.alert-error {
    background: rgba(248, 81, 73, 0.1);
    border: 1px solid rgba(248, 81, 73, 0.3);
    color: var(--red);
}

.alert-success {
    background: rgba(63, 185, 80, 0.1);
    border: 1px solid rgba(63, 185, 80, 0.3);
    color: var(--green);
}

/* ===== 响应式 ===== */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }

    .nav-links {
        position: fixed;
        top: 60px;
        left: 0;
        right: 0;
        background: var(--bg-secondary);
        flex-direction: column;
        padding: 20px;
        gap: 16px;
        border-bottom: 1px solid var(--border);
        transform: translateY(-100%);
        opacity: 0;
        pointer-events: none;
        transition: var(--transition);
    }

    .nav-links.open {
        transform: translateY(0);
        opacity: 1;
        pointer-events: auto;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: 24px;
    }

    .section {
        padding: 48px 0;
    }

    .section-title {
        font-size: 24px;
    }
}