:root {
  --primary: #1a56db;
  --primary-dark: #1240a8;
  --correct: #057a55;
  --wrong: #c81e1e;
  --bg: #f3f4f6;
  --card: #fff;
  --border: #e5e7eb;
  --text: #111827;
  --muted: #6b7280;
  --accent: #7c3aed;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

/* ── Header ─────────────────────────────────────────── */
.site-header {
  background: linear-gradient(135deg, #1e3a8a, #1a56db 60%, #7c3aed);
  color: #fff;
  padding: 2rem 1.5rem 1.5rem;
  text-align: center;
  box-shadow: 0 4px 20px rgba(0,0,0,.25);
}
.site-header h1 {
  font-size: clamp(1.3rem, 3vw, 1.9rem);
  font-weight: 700;
  letter-spacing: -.02em;
}
.site-header p { opacity: .85; margin-top: .4rem; font-size: .93rem; }

/* ── Score bar ───────────────────────────────────────── */
.score-bar {
  background: #fff;
  border-bottom: 1px solid var(--border);
  padding: .75rem 1.5rem;
  display: flex;
  align-items: center;
  gap: 1.5rem;
  flex-wrap: wrap;
  position: sticky;
  top: 0;
  z-index: 50;
  box-shadow: 0 2px 8px rgba(0,0,0,.06);
}
.stat { font-size: .85rem; color: var(--muted); }
.stat strong { color: var(--text); font-size: 1rem; }
.reset-btn {
  margin-left: auto;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 6px;
  padding: .45rem 1rem;
  font-size: .85rem;
  cursor: pointer;
}
.reset-btn:hover { background: var(--primary-dark); }

/* ── Progress bar ────────────────────────────────────── */
.progress-wrap { padding: .6rem 1.5rem .2rem; }
.progress-outer {
  height: 6px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
}
.progress-inner {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  border-radius: 999px;
  transition: width .4s;
  width: 0;
}
.progress-text { font-size: .78rem; color: var(--muted); margin-top: .3rem; }

/* ── Filter tabs ─────────────────────────────────────── */
.filter-tabs {
  display: flex;
  gap: .5rem;
  padding: 1rem 1.5rem .5rem;
  flex-wrap: wrap;
}
.filter-tab {
  border: 1.5px solid var(--border);
  background: #fff;
  border-radius: 999px;
  padding: .35rem .9rem;
  font-size: .82rem;
  cursor: pointer;
  color: var(--muted);
  transition: all .15s;
}
.filter-tab:hover,
.filter-tab.active {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

/* ── Cards ───────────────────────────────────────────── */
.cards-container {
  max-width: 860px;
  margin: 0 auto;
  padding: 1rem 1rem 3rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}
.question-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  box-shadow: 0 1px 4px rgba(0,0,0,.05);
  transition: box-shadow .2s;
}
.question-card:hover { box-shadow: 0 4px 16px rgba(0,0,0,.1); }
.question-card.answered-correct { border-left: 4px solid var(--correct); }
.question-card.answered-wrong   { border-left: 4px solid var(--wrong); }

/* ── Question header ─────────────────────────────────── */
.question-header {
  display: flex;
  align-items: center;
  gap: .6rem;
  margin-bottom: .9rem;
  flex-wrap: wrap;
}
.q-number { font-weight: 700; font-size: .95rem; color: var(--primary); }
.badge {
  font-size: .7rem;
  font-weight: 600;
  padding: .2rem .55rem;
  border-radius: 999px;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.badge-single { background: #dbeafe; color: #1e40af; }
.badge-multi  { background: #ede9fe; color: #5b21b6; }
.q-status { font-size: .8rem; font-weight: 600; margin-left: auto; }
.q-status.correct { color: var(--correct); }
.q-status.wrong   { color: var(--wrong); }

/* ── Question body ───────────────────────────────────── */
.question-text { font-size: 1rem; line-height: 1.65; margin-bottom: 1.1rem; }

.options-group {
  display: flex;
  flex-direction: column;
  gap: .55rem;
  margin-bottom: 1rem;
}
.option-label {
  display: flex;
  align-items: flex-start;
  gap: .7rem;
  padding: .7rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  line-height: 1.45;
  transition: all .15s;
}
.option-label:hover { border-color: var(--primary); background: #eff6ff; }
.option-label.r-correct  { border-color: var(--correct) !important; background: #f0fdf4 !important; }
.option-label.r-wrong    { opacity: .5; }
.option-label.r-sel-wrong { border-color: var(--wrong) !important; background: #fff1f1 !important; }

.option-input  { width: 1.1rem; height: 1.1rem; margin-top: .1rem; flex-shrink: 0; accent-color: var(--primary); }
.option-letter { font-weight: 700; color: var(--primary); flex-shrink: 0; min-width: 1.2rem; }

/* ── Footer / buttons ────────────────────────────────── */
.question-footer {
  display: flex;
  gap: .6rem;
  margin-top: .5rem;
  flex-wrap: wrap;
  align-items: center;
}
.btn-answer, .btn-explain {
  border: none;
  border-radius: 7px;
  padding: .5rem 1.1rem;
  font-size: .88rem;
  font-weight: 600;
  cursor: pointer;
  transition: all .2s;
}
.btn-answer { background: var(--primary); color: #fff; }
.btn-answer:hover { background: var(--primary-dark); transform: translateY(-1px); }
.btn-answer:disabled { background: #9ca3af; cursor: not-allowed; transform: none; }

.btn-explain { background: #fff; color: var(--accent); border: 1.5px solid var(--accent); }
.btn-explain:hover { background: var(--accent); color: #fff; }

.answer-reveal {
  margin-top: .75rem;
  padding: .6rem 1rem;
  background: #f0fdf4;
  border-radius: 7px;
  border: 1px solid #a7f3d0;
}
.correct-badge { font-weight: 700; color: var(--correct); font-size: .92rem; }

/* ── Modal ───────────────────────────────────────────── */
.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.55);
  z-index: 1000;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}
.modal-overlay.open { display: flex; }
.modal {
  background: #fff;
  border-radius: 14px;
  max-width: 720px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: 0 20px 60px rgba(0,0,0,.35);
  animation: slideIn .2s ease;
}
@keyframes slideIn {
  from { transform: translateY(-20px); opacity: 0; }
  to   { transform: translateY(0);     opacity: 1; }
}
.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.2rem 1.5rem 1rem;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: #fff;
  z-index: 1;
}
.modal-header h2 { font-size: 1.05rem; font-weight: 700; color: var(--primary); }
.modal-close {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  color: var(--muted);
  line-height: 1;
  padding: .2rem .4rem;
  border-radius: 4px;
}
.modal-close:hover { background: var(--bg); }
.modal-body {
  padding: 1.2rem 1.5rem 1.5rem;
  font-size: .93rem;
  line-height: 1.75;
  color: #374151;
}
.modal-body a { color: var(--primary); word-break: break-all; }

/* ── Responsive ──────────────────────────────────────── */
@media (max-width: 600px) {
  .question-card { padding: 1.1rem; }
  .option-label  { padding: .6rem .8rem; }
}