@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;700&display=swap');
:root{
  --primary: #0d6efd;
  --accent: #60a5fa;
  --bg: #f8fafc;
  --card: rgba(255,255,255,0.75);
  --glass: rgba(255,255,255,0.6);
  --text: #0b1220;
  --muted: #64748b;
  --success: #16a34a;
}
[data-theme="dark"]{
  --primary: #60a5fa;
  --accent: #1e3a8a;
  --bg: #071127;
  --card: rgba(8,16,30,0.65);
  --glass: rgba(8,16,30,0.5);
  --text: #e6eef8;
  --muted: #94a3b8;
  --success: #4ade80;
}
*{box-sizing:border-box}
html,body{height:100%;margin:0;font-family:Inter, system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial;background:linear-gradient(180deg,var(--bg),#ffffff);color:var(--text);-webkit-font-smoothing:antialiased}
.header{position:sticky;top:0;z-index:50;backdrop-filter:blur(8px);background:var(--glass);display:flex;align-items:center;justify-content:space-between;padding:14px 24px;border-bottom:1px solid rgba(15,23,42,0.04)}
.brand{display:flex;gap:12px;align-items:center}
.logo{width:40px;height:40px;border-radius:8px;background:linear-gradient(135deg,var(--primary),var(--accent));display:flex;align-items:center;justify-content:center;color:white;font-weight:700;font-size:18px;box-shadow:0 6px 18px rgba(13,110,253,0.12)}
.nav a{margin-left:14px;text-decoration:none;color:var(--text);font-weight:500}
.container{max-width:1100px;margin:28px auto;padding:0 20px}
.hero{display:flex;gap:20px;align-items:center;padding:28px;border-radius:16px;background:linear-gradient(180deg,rgba(13,110,253,0.06),rgba(96,165,250,0.02));box-shadow:0 12px 40px rgba(2,6,23,0.06)}
.hero .left{flex:1}
.hero h1{margin:0;font-size:34px;line-height:1.05}
.hero p{margin:12px 0;color:var(--muted)}
.cta-row{display:flex;gap:12px;margin-top:12px}
.btn{background:var(--primary);color:white;padding:10px 16px;border-radius:12px;border:none;cursor:pointer;font-weight:600;box-shadow:0 8px 24px rgba(13,110,253,0.12)}
.btn.ghost{background:transparent;color:var(--primary);border:1px solid rgba(13,110,253,0.12)}

.grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin-top:20px}
.card{background:var(--card);padding:18px;border-radius:12px;box-shadow:0 10px 30px rgba(2,6,23,0.06);border:1px solid rgba(15,23,42,0.04)}

.lesson-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:12px;margin-top:14px}
.lesson{padding:12px;border-radius:10px;background:linear-gradient(180deg,rgba(255,255,255,0.02),transparent);border:1px solid rgba(15,23,42,0.04)}

.footer{margin-top:36px;padding:28px 0;text-align:center;color:var(--muted)}

.small{font-size:13px;color:var(--muted)}

/* responsive */
@media (max-width:900px){
  .hero{flex-direction:column;align-items:flex-start}
  .grid{grid-template-columns:1fr}
}
.icon-btn{display:inline-flex;align-items:center;gap:8px;padding:8px 10px;border-radius:10px;border:1px solid rgba(15,23,42,0.04);background:transparent;cursor:pointer}

/* audio player */
.audio-player{display:flex;align-items:center;gap:10px}
.wave{width:160px;height:20px;background:linear-gradient(90deg,rgba(13,110,253,0.16),rgba(96,165,250,0.06));border-radius:6px}

/* progress pill */
.pill{display:inline-block;padding:6px 10px;border-radius:999px;background:rgba(13,110,253,0.08);color:var(--primary);font-weight:600}

/* theme toggle group */
.theme-switch{display:inline-flex;gap:8px;align-items:center;border-radius:999px;padding:6px;background:rgba(15,23,42,0.02);border:1px solid rgba(15,23,42,0.03)}
.theme-switch button{background:none;border:none;padding:6px 8px;border-radius:8px;cursor:pointer}