:root {
    --primary: #4fc3f7;
    --primary-gradient: linear-gradient(135deg, #4fc3f7, #29b6f6);
    --text: #1a1a1a;
    --subtext: #555;
    --muted: #888;
    --bg: #f9f9f9;
    --card: #ffffff;
    --card-hover: #ffffff;
    --border: #e8e8e8;
    --footer-bg: #f0f0f0;
    --header-bg: rgba(255,255,255,0.85);
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.1);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --code-bg: #1a2332;
    --code-text: #e0e0e0;
}
* { margin: 0; padding: 0; box-sizing: border-box; font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', system-ui, -apple-system, sans-serif; }
body {
    line-height: 1.7;
    color: var(--text);
    background-color: var(--bg);
    transition: background-color 0.3s, color 0.3s;
    -webkit-font-smoothing: antialiased;
}
header {
    background-color: var(--header-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    box-shadow: var(--shadow-sm);
    position: fixed;
    width: 100%;
    z-index: 100;
    transition: background-color 0.3s, color 0.3s;
}
.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }
nav { display: flex; justify-content: space-between; align-items: center; padding: 20px 0; }
.logo {
    font-size: 24px; font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text; text-decoration: none; letter-spacing: -0.5px;
}
.nav-links { display: flex; list-style: none; }
.nav-links li { margin-left: 30px; }
.nav-links a { text-decoration: none; color: var(--text); font-weight: 500; transition: color 0.3s; }
.nav-links a:hover, .nav-links a.active { color: var(--primary); }

/* 主题切换按钮 */
.theme-toggle-btn {
    background: none; border: 1px solid var(--border); cursor: pointer;
    font-size: 1rem; color: var(--text); padding: 8px 10px;
    border-radius: 50%; transition: all 0.2s;
    width: 36px; height: 36px; display: flex; align-items: center; justify-content: center;
}
.theme-toggle-btn:hover { background: var(--card); border-color: var(--primary); color: var(--primary); }

.hero { height: 100vh; display: flex; align-items: center; position: relative; padding-top: 80px; }
.hero-content { max-width: 600px; position: relative; z-index: 10; }
.hero h1 {
    font-size: 56px; margin-bottom: 20px; font-weight: 800;
    background: var(--primary-gradient);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text; letter-spacing: -1px;
}
.hero p { font-size: 18px; margin-bottom: 30px; color: var(--subtext); line-height: 1.8; }
.hero-buttons { display: flex; gap: 15px; }
.btn {
    display: inline-block; background: var(--primary-gradient); color: #fff;
    padding: 14px 32px; border-radius: var(--radius-sm); text-decoration: none;
    font-weight: 600; font-size: 0.95rem; border: none; cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 4px 14px rgba(79, 195, 247, 0.3);
}
.btn:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(79, 195, 247, 0.4); }
.btn-outline { background: transparent; color: var(--primary); border: 2px solid var(--primary); box-shadow: none; }
.btn-outline:hover { background: var(--primary-gradient); color: #fff; border-color: transparent; box-shadow: 0 6px 20px rgba(79, 195, 247, 0.4); }
section { padding: 100px 0; position: relative; }
.section-title {
    text-align: center; margin-bottom: 60px; font-size: 36px; font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text; letter-spacing: -0.5px;
}
.about-content { display: flex; align-items: center; gap: 50px; }
.about-text { flex: 1; color: var(--text); }
.about-image { flex: 1; border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow-lg); transition: transform 0.3s ease; }
.about-image:hover { transform: scale(1.02); }
.about-image img { width: 100%; height: auto; display: block; }
.services { background: var(--bg); }
.services-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 30px; }
.service-card {
    background: var(--card); padding: 36px 30px; border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm); color: var(--text);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    border: 1px solid var(--border); position: relative; overflow: hidden;
}
.service-card::before {
    content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
    background: var(--primary-gradient); transform: scaleX(0);
    transform-origin: left; transition: transform 0.3s ease;
}
.service-card:hover::before { transform: scaleX(1); }
.service-card:hover { transform: translateY(-6px); box-shadow: var(--shadow-lg); border-color: transparent; }
.service-card h3 { margin-bottom: 15px; font-size: 22px; color: var(--primary); }
.form-group { margin-bottom: 20px; }
.form-group label { display: block; margin-bottom: 5px; color: var(--text); }
.form-group input, .form-group textarea {
    width: 100%; padding: 14px 16px; border: 1.5px solid var(--border);
    border-radius: var(--radius-sm); background: var(--card); color: var(--text);
    transition: all 0.3s ease; font-size: 0.95rem;
}
.form-group input:focus, .form-group textarea:focus { border-color: var(--primary); outline: none; box-shadow: 0 0 0 3px rgba(79, 195, 247, 0.12); }
.form-group textarea { height: 150px; }
footer {
    background: var(--footer-bg); color: var(--muted); padding: 50px 0; text-align: center;
    border-top: 1px solid var(--border); font-size: 0.9rem; transition: background-color 0.3s, color 0.3s;
}
.footer-links { display: flex; justify-content: center; list-style: none; margin-bottom: 30px; }
.footer-links li { margin: 0 15px; }
.footer-links a { color: var(--muted); text-decoration: none; transition: color 0.2s; font-size: 0.9rem; }
.footer-links a:hover { color: var(--primary); }
#particles-js { position: absolute; width: 100%; height: 100%; top: 0; left: 0; z-index: 1; }
.contact-content { display: flex; gap: 50px; color: var(--text); }
.contact-info { flex: 1; }
.contact-info ul { list-style: none; padding: 0; }
.contact-info li { margin-bottom: 20px; }
.contact-info strong { color: var(--primary); display: block; margin-bottom: 5px; }
.contact-form {
    flex: 1; background: var(--card); padding: 36px; border-radius: var(--radius-md);
    box-shadow: var(--shadow-md); border: 1px solid var(--border);
}
.contact-email-card {
    display: flex; align-items: center; gap: 16px; padding: 24px;
    background: var(--card); border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm); border: 1px solid var(--border); transition: all 0.3s ease;
}
.contact-email-card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); border-color: var(--primary); }
.contact-email-card i { font-size: 2rem; color: var(--primary); }
.contact-email-card a { font-size: 1.1rem; color: var(--text); text-decoration: none; font-weight: 500; transition: color 0.2s; }
.contact-email-card a:hover { color: var(--primary); }
.error-page { padding-top: 200px; text-align: center; min-height: 80vh; }
.error-page h1 { font-size: 6rem; color: var(--primary); }
.error-page p { font-size: 1.3rem; color: var(--muted); margin-bottom: 30px; }

/* 粒子背景暗色适配 */
.dark #particles-js canvas { filter: invert(1) hue-rotate(180deg); opacity: 0.15; }

/* ============================
   暗色主题
   ============================ */
.dark {
    --primary: #58a6ff;
    --primary-gradient: linear-gradient(135deg, #58a6ff, #3b82f6);
    --text: #e6edf3;
    --subtext: #8b949e;
    --muted: #6e7681;
    --bg: #0d1117;
    --card: #161b22;
    --card-hover: #1c2333;
    --border: #30363d;
    --footer-bg: #0d1117;
    --header-bg: rgba(13, 17, 23, 0.92);
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.5);
    --code-bg: #0d1117;
    --code-text: #e6edf3;
}
.dark header { box-shadow: 0 1px 0 rgba(255,255,255,0.04); }
.dark .form-group input:focus, .dark .form-group textarea:focus { box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.15); }
.dark .service-card:hover { border-color: var(--border); }
.dark .contact-email-card:hover { border-color: var(--primary); }
.dark .btn-outline { color: var(--primary); border-color: var(--primary); }
.dark .btn-outline:hover { background: var(--primary-gradient); color: #fff; }
.dark .theme-toggle-btn i { content: "\f185"; }

/* 响应式 */
@media (max-width: 768px) {
    .hero h1 { font-size: 32px; }
    .hero p { font-size: 16px; }
    .about-content, .contact-content { flex-direction: column; }
    .nav-links li { margin-left: 15px; }
}