/* === Base reset === */
*{box-sizing:border-box;margin:0;padding:0}
:root{
  --bg-1: #0f1724; --bg-2:#172033; --accent: #00ffcc; --gold:#ffcc00; --card:#0f3460; --glass: rgba(255,255,255,0.04);
}
html,body{height:100%}
body{
  font-family: Inter, system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial;
  background: linear-gradient(135deg,var(--bg-1),var(--bg-2));
  color: #e6eef6;
  min-height:100vh;
  position:relative;
  padding:24px;
  -webkit-font-smoothing:antialiased;
}

/* particle canvas sits behind everything */
#particles-js{position:fixed;inset:0;z-index:0}

.topbar{position:relative;z-index:5;display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:18px}
#appTitle{font-size:1.4rem;color:var(--gold)}
.top-controls{display:flex;gap:8px}
.top-controls button{background:var(--glass);border:none;color:inherit;padding:8px;border-radius:8px;cursor:pointer}

main{position:relative;z-index:5;display:flex;flex-direction:column;gap:18px;align-items:center}
.subtitle{opacity:0.9;margin-bottom:6px}

/* subjects */
.subject-buttons{display:flex;flex-wrap:wrap;gap:10px;justify-content:center}
.subjectBtn{background:linear-gradient(180deg,var(--card),#123a5b);border:none;color:#fff;padding:10px 14px;border-radius:10px;min-width:64px;cursor:pointer;transform:translateY(0);transition:transform .25s,box-shadow .25s}
.subjectBtn:hover{transform:translateY(-6px);box-shadow:0 12px 24px rgba(0,0,0,0.45)}

/* card */
.container{display:none;width:100%;max-width:820px}
.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 10px 30px rgba(0,0,0,0.4);}
.card-header{display:flex;flex-direction:column;gap:8px;margin-bottom:10px}
#subjectTitle{color:var(--gold)}
.progress-bar{height:10px;background:rgba(255,255,255,0.03);border-radius:10px;overflow:hidden}
.progress-bar-inner{height:100%;width:0;background:linear-gradient(90deg,var(--accent),#7afcff);transition:width .4s ease}
.card-body{padding:8px 0}
.question{font-weight:600;font-size:1.1rem;margin-bottom:10px}
.choices{display:flex;flex-direction:column;gap:10px}
.choice{background:var(--glass);padding:12px;border-radius:10px;cursor:pointer;transition:transform .18s,background .18s,box-shadow .18s}
.choice:hover{transform:translateY(-4px);box-shadow:0 8px 20px rgba(0,0,0,0.4)}
.choice.selected.correct{background:#198754;color:#fff}
.choice.selected.wrong{background:#dc3545;color:#fff}

.card-footer{display:flex;flex-direction:column;gap:8px;margin-top:12px}
.navigation{display:flex;justify-content:space-between}
.prevBtn,.nextBtn{background:var(--gold);border:none;padding:10px 16px;border-radius:10px;cursor:pointer}
.timer{font-weight:700;color:var(--accent);text-align:center}
.timer.warning{color:#ff6b6b;animation:blink .9s infinite}
@keyframes blink{0%,50%,100%{opacity:1}25%,75%{opacity:0}}

/* score & leaderboard */
.scoreCard{display:none;background:var(--glass);padding:14px;border-radius:10px;color:var(--accent);text-align:center}
.leaderboard{width:100%;max-width:820px;padding:14px;border-radius:10px;background:rgba(255,255,255,0.02)}
.leaderboard h3{color:var(--gold);margin-bottom:8px}
.leaderboard ul{list-style:none}
.leaderboard li{padding:8px 0;border-bottom:1px solid rgba(255,255,255,0.03)}

/* notes */
.notes-container{display:none;width:100%;max-width:900px;padding:12px;border-radius:10px;background:rgba(255,255,255,0.02)}
.notes-controls{display:flex;gap:10px;justify-content:center}
#toggleNotes{background:#00adb5;border:none;color:#fff;padding:8px 14px;border-radius:8px;cursor:pointer}
#downloadPDF{background:var(--gold);color:#000;padding:8px 12px;border-radius:8px;text-decoration:none}
iframe{width:100%;height:420px;border-radius:8px;border:none;margin-top:10px}

/* small alerts */
.alert{position:fixed;top:20px;left:50%;transform:translateX(-50%);background:#ff6b6b;color:#fff;padding:8px 12px;border-radius:8px;z-index:999}

/* responsive */
@media (max-width:900px){.card{padding:14px}.question{font-size:1rem}iframe{height:300px}}
@media (max-width:600px){#appTitle{font-size:1.1rem}.subjectBtn{padding:8px 10px}}