/* ===== Reset & Base ===== */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{
  --c-primary:#2563eb;
  --c-primary-dark:#1d4ed8;
  --c-accent:#f59e0b;
  --c-bg:#ffffff;
  --c-bg-alt:#f8fafc;
  --c-text:#1e293b;
  --c-text-light:#64748b;
  --c-border:#e2e8f0;
  --max-w:1120px;
  --radius:12px;
  --shadow:0 1px 3px rgba(0,0,0,.08),0 1px 2px rgba(0,0,0,.04);
  --shadow-lg:0 10px 25px rgba(0,0,0,.08);
  --transition:all .25s ease;
}
html{scroll-behavior:smooth;font-size:16px}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Noto Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  color:var(--c-text);background:var(--c-bg);line-height:1.7;
}
a{color:var(--c-primary);text-decoration:none;transition:var(--transition)}
a:hover{color:var(--c-primary-dark)}
img{max-width:100%;display:block}
.container{max-width:var(--max-w);margin:0 auto;padding:0 24px}

/* ===== Header / Nav ===== */
.site-header{
  position:sticky;top:0;z-index:100;
  background:rgba(255,255,255,.88);backdrop-filter:blur(12px);
  border-bottom:1px solid var(--c-border);
}
.site-header .container{
  display:flex;align-items:center;justify-content:space-between;
  height:64px;
}
.logo{font-size:1.25rem;font-weight:700;color:var(--c-text);display:flex;align-items:center;gap:8px}
.logo span{color:var(--c-primary)}
.nav-links{display:flex;gap:28px;list-style:none}
.nav-links a{color:var(--c-text-light);font-size:.94rem;font-weight:500;position:relative}
.nav-links a::after{content:'';position:absolute;bottom:-4px;left:0;width:0;height:2px;background:var(--c-primary);transition:var(--transition)}
.nav-links a:hover,
.nav-links a.active{color:var(--c-primary)}
.nav-links a:hover::after,
.nav-links a.active::after{width:100%}

/* mobile toggle */
.menu-toggle{display:none;background:none;border:none;cursor:pointer;padding:4px}
.menu-toggle svg{width:24px;height:24px;stroke:var(--c-text)}

/* ===== Hero ===== */
.hero{
  padding:80px 0 60px;
  background:linear-gradient(135deg,#eff6ff 0%,#f8fafc 100%);
}
.hero .container{display:flex;align-items:center;gap:48px}
.hero-text{flex:1}
.hero-text h1{font-size:2.5rem;font-weight:800;line-height:1.25;margin-bottom:16px}
.hero-text h1 span{color:var(--c-primary)}
.hero-text p{font-size:1.1rem;color:var(--c-text-light);margin-bottom:28px;max-width:500px}
.hero-visual{flex:1;display:flex;justify-content:center}
.hero-visual .hero-card{
  width:340px;padding:36px;border-radius:var(--radius);
  background:#fff;box-shadow:var(--shadow-lg);text-align:center;
}
.hero-card .icon-circle{
  width:72px;height:72px;border-radius:50%;margin:0 auto 20px;
  background:linear-gradient(135deg,var(--c-primary),#60a5fa);
  display:flex;align-items:center;justify-content:center;
}
.hero-card .icon-circle svg{width:36px;height:36px;stroke:#fff;fill:none;stroke-width:2}
.hero-card h3{font-size:1.15rem;margin-bottom:8px}
.hero-card p{font-size:.9rem;color:var(--c-text-light)}

/* Buttons */
.btn{
  display:inline-flex;align-items:center;gap:6px;
  padding:12px 28px;border-radius:8px;font-weight:600;font-size:.95rem;
  transition:var(--transition);cursor:pointer;border:none;
}
.btn-primary{background:var(--c-primary);color:#fff}
.btn-primary:hover{background:var(--c-primary-dark);color:#fff;transform:translateY(-1px);box-shadow:var(--shadow-lg)}
.btn-outline{border:1.5px solid var(--c-primary);color:var(--c-primary);background:transparent}
.btn-outline:hover{background:var(--c-primary);color:#fff}

/* ===== Section common ===== */
.section{padding:72px 0}
.section-title{font-size:1.75rem;font-weight:700;text-align:center;margin-bottom:12px}
.section-subtitle{text-align:center;color:var(--c-text-light);margin-bottom:48px;max-width:560px;margin-left:auto;margin-right:auto}

/* ===== Features / Highlights ===== */
.features-grid{
  display:grid;grid-template-columns:repeat(3,1fr);gap:28px;
}
.feature-card{
  padding:32px 24px;border-radius:var(--radius);background:var(--c-bg);
  border:1px solid var(--c-border);transition:var(--transition);
}
.feature-card:hover{border-color:var(--c-primary);box-shadow:var(--shadow-lg);transform:translateY(-3px)}
.feature-card .icon{
  width:48px;height:48px;border-radius:10px;margin-bottom:16px;
  display:flex;align-items:center;justify-content:center;
  background:#eff6ff;
}
.feature-card .icon svg{width:24px;height:24px;stroke:var(--c-primary);fill:none;stroke-width:2}
.feature-card h3{font-size:1.1rem;margin-bottom:8px}
.feature-card p{font-size:.9rem;color:var(--c-text-light)}

/* ===== Course Section ===== */
.course-section{background:var(--c-bg-alt)}
.course-list{display:flex;flex-direction:column;gap:20px;max-width:780px;margin:0 auto}
.course-item{
  display:flex;align-items:flex-start;gap:20px;
  padding:24px;border-radius:var(--radius);background:#fff;
  border:1px solid var(--c-border);transition:var(--transition);
}
.course-item:hover{box-shadow:var(--shadow);border-color:var(--c-primary)}
.course-num{
  flex-shrink:0;width:44px;height:44px;border-radius:10px;
  background:var(--c-primary);color:#fff;font-weight:700;font-size:1.1rem;
  display:flex;align-items:center;justify-content:center;
}
.course-item h3{font-size:1.05rem;margin-bottom:4px}
.course-item p{font-size:.88rem;color:var(--c-text-light)}

/* ===== Blog List ===== */
.blog-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:28px}
.blog-card{
  border-radius:var(--radius);overflow:hidden;
  border:1px solid var(--c-border);transition:var(--transition);background:#fff;
}
.blog-card:hover{box-shadow:var(--shadow-lg);transform:translateY(-3px)}
.blog-card .thumb{
  height:180px;background:linear-gradient(135deg,#dbeafe,#ede9fe);
  display:flex;align-items:center;justify-content:center;
}
.blog-card .thumb svg{width:48px;height:48px;stroke:var(--c-primary);opacity:.5;fill:none;stroke-width:1.5}
.blog-card .card-body{padding:20px}
.blog-card .tag{
  display:inline-block;font-size:.75rem;font-weight:600;
  color:var(--c-primary);background:#eff6ff;padding:3px 10px;border-radius:20px;margin-bottom:10px;
}
.blog-card h3{font-size:1.05rem;margin-bottom:6px}
.blog-card h3 a{color:var(--c-text)}
.blog-card h3 a:hover{color:var(--c-primary)}
.blog-card .meta{font-size:.8rem;color:var(--c-text-light)}
.blog-card .excerpt{font-size:.88rem;color:var(--c-text-light);margin-top:8px;
  display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;}

/* ===== Blog Article Page ===== */
.article-header{padding:48px 0 24px;background:var(--c-bg-alt);text-align:center}
.article-header h1{font-size:2rem;max-width:720px;margin:0 auto 12px}
.article-header .meta{color:var(--c-text-light);font-size:.9rem}
.article-content{max-width:720px;margin:0 auto;padding:40px 24px 80px}
.article-content h2{font-size:1.4rem;margin:32px 0 12px;padding-top:16px;border-top:1px solid var(--c-border)}
.article-content h3{font-size:1.15rem;margin:24px 0 8px}
.article-content p{margin-bottom:16px}
.article-content ul,.article-content ol{margin:0 0 16px 24px}
.article-content li{margin-bottom:6px}
.article-content blockquote{
  border-left:3px solid var(--c-primary);margin:20px 0;padding:12px 20px;
  background:#f8fafc;border-radius:0 8px 8px 0;color:var(--c-text-light);font-style:italic;
}
.article-content code{background:#f1f5f9;padding:2px 6px;border-radius:4px;font-size:.9em}
.article-content pre{background:#1e293b;color:#e2e8f0;padding:20px;border-radius:8px;overflow-x:auto;margin-bottom:16px}
.article-content pre code{background:transparent;padding:0;color:inherit}
.article-content img{border-radius:8px;margin:20px 0}

/* ===== CTA ===== */
.cta{
  padding:64px 0;text-align:center;
  background:linear-gradient(135deg,var(--c-primary) 0%,#7c3aed 100%);color:#fff;
}
.cta h2{font-size:1.75rem;margin-bottom:12px}
.cta p{opacity:.85;margin-bottom:28px;max-width:480px;margin-left:auto;margin-right:auto}
.cta .btn-primary{background:#fff;color:var(--c-primary)}
.cta .btn-primary:hover{background:#f1f5f9}

/* ===== Footer ===== */
.site-footer{
  padding:40px 0;background:#1e293b;color:#94a3b8;font-size:.88rem;
}
.footer-inner{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:16px}
.footer-links{display:flex;gap:20px;list-style:none}
.footer-links a{color:#94a3b8}
.footer-links a:hover{color:#fff}

/* ===== Responsive ===== */
@media(max-width:768px){
  .hero .container{flex-direction:column;text-align:center}
  .hero-text h1{font-size:1.8rem}
  .hero-text p{margin-left:auto;margin-right:auto}
  .hero-visual .hero-card{width:280px;padding:28px}
  .features-grid{grid-template-columns:1fr}
  .blog-grid{grid-template-columns:1fr}
  .nav-links{
    display:none;position:absolute;top:64px;left:0;right:0;
    flex-direction:column;background:#fff;padding:16px 24px;gap:12px;
    border-bottom:1px solid var(--c-border);box-shadow:var(--shadow);
  }
  .nav-links.open{display:flex}
  .menu-toggle{display:block}
  .footer-inner{flex-direction:column;text-align:center}
}