:root{
      --bg:#0f1724; --card:#0b1220; --accent:#06b6d4; --muted:#94a3b8; --glass: rgba(255,255,255,0.04);
      --success:#10b981; --danger:#ef4444; --gold:#f59e0b;
      font-family: Inter, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
    }
    *{box-sizing:border-box}
    html,body{height:100%;margin:0;background:linear-gradient(180deg,#071028 0%, #0f1724 100%);color:#e6eef6}
    .container{max-width:1100px;margin:15px auto;padding:10px}
    header{display:flex;align-items:center;justify-content:space-between;margin-bottom:18px}
    .brand{display:flex;gap:12px;align-items:center}
    .logo{width:66px;height:66px;border-radius:12px;background:linear-gradient(135deg,var(--accent),#7c3aed);display:flex;align-items:center;justify-content:center;font-weight:700}
    .title{font-size:20px;font-weight:700}
    .subtitle{color:var(--muted);font-size:13px}

    /* Topic cards */
    .topics{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:18px;width: 100%;}
    .card{background:linear-gradient(180deg, rgba(255,255,255,0.02), rgba(255,255,255,0.01));border-radius:14px;padding:18px;box-shadow:0 6px 20px rgba(2,6,23,0.6);transition:transform .18s ease,box-shadow .18s}
    .card:hover{transform:translateY(-6px);box-shadow:0 20px 40px rgba(2,6,23,0.7)}
    .card h3{margin:0 0 6px 0}
    .card p{margin:0;color:var(--muted);font-size:13px}
    .start-btn{margin-top:12px;padding:10px 14px;background:var(--accent);border:none;border-radius:10px;color:#002;cursor:pointer;font-weight:700}

    /* Quiz area */
    .quiz{display:none;margin-top:20px}
    .quiz.active{display:block}
    .topbar{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}
    .progress{flex:1;height:10px;background:var(--glass);border-radius:999px;overflow:hidden;margin:0 12px}
    .progress > i{display:block;height:100%;background:linear-gradient(90deg,var(--accent),#7c3aed);width:0%}
    .timer{font-weight:700;color:var(--gold)}
    .question-card{background:linear-gradient(180deg, rgba(255,255,255,0.02), rgba(255,255,255,0.01));padding:20px;border-radius:12px}
    .question{font-size:18px;margin-bottom:12px}
    .choices{display:grid;gap:10px}
    .choice{padding:12px;border-radius:10px;background:transparent;border:1px solid rgba(255,255,255,0.04);cursor:pointer}
    .choice:hover{border-color:rgba(255,255,255,0.08);transform:translateY(-3px)}
    .choice.selected{background:linear-gradient(90deg, rgba(6,182,212,0.12), rgba(124,58,237,0.08));border-color:rgba(6,182,212,0.2)}
    .controls{display:flex;justify-content:space-between;align-items:center;margin-top:12px}

    /* Results */
    .results{display:none;margin-top:18px}
    .results.active{display:block}
    .score{font-size:28px;font-weight:800}
    .details{margin-top:12px}
    .q-row{display:flex;justify-content:space-between;padding:10px;border-radius:8px;margin-bottom:8px;background:rgba(255,255,255,0.016)}
    .q-row .q-left{max-width:70%}
    .badge{padding:6px 8px;border-radius:999px;font-weight:700}
    .badge.correct{background:rgba(16,185,129,0.12);color:var(--success)}
    .badge.wrong{background:rgba(239,68,68,0.08);color:var(--danger)}

    /* footer */
    footer{margin-top:28px;color:var(--muted);font-size:13px;text-align:center}

    /* Responsive */
    @media (max-width:640px){
      .container{padding:12px 25px}
      .logo{width:48px;height:48px}
      .title{
         font-size:16px;font-weight:500
      }
      .subtitle{
         display: none;
      }
   }


    #topicSelect{
      min-height: 60vh;
      display: flex;
      align-items: center;
      justify-content: center;
      flex-direction: row;
    }
    #select_language{
      padding: 5px;
      border-radius: 15px;
      color: #ffffff;
      background-color: #06b6d4;
    }
    #select_language option{
      text-align: center;
    }

    .ads{
      display: flex;
      justify-content: center;
      align-items: center;
      flex-direction: column;
      margin-top: 50px;
    }