:root {
  --bg: #f4f6fb;
  --surface: #ffffff;
  --surface-2: #f0f2f8;
  --border: #dde2ee;
  --text: #1a2033;
  --muted: #5d6680;
  --primary: #3b5bdb;
  --primary-hover: #2f4bc0;
  --primary-soft: #e7ecff;
  --success: #2b8a3e;
  --success-soft: #e6f6ea;
  --danger: #c92a2a;
  --danger-soft: #fdeaea;
  --warning: #e8890c;
  --warning-soft: #fff4e2;
  --shadow: 0 1px 2px rgba(20, 30, 60, .06), 0 4px 16px rgba(20, 30, 60, .06);
  --radius: 14px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1320;
    --surface: #181d2e;
    --surface-2: #20263a;
    --border: #2d3550;
    --text: #e6e9f2;
    --muted: #9aa3bd;
    --primary: #6c8cff;
    --primary-hover: #8aa3ff;
    --primary-soft: #232c4d;
    --success: #51cf66;
    --success-soft: #1b3324;
    --danger: #ff6b6b;
    --danger-soft: #3a1f24;
    --warning: #ffb347;
    --warning-soft: #3a2e1a;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 16px rgba(0, 0, 0, .25);
  }
}

* { box-sizing: border-box; }

html, body { margin: 0; padding: 0; }

body {
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

h1, h2 { margin: 0; line-height: 1.2; }
.muted { color: var(--muted); }
.center { text-align: center; }

.screen { display: none; min-height: 100vh; }
.screen.active { display: block; }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

/* Botones */
.btn {
  font: inherit;
  font-weight: 600;
  font-size: .95rem;
  border: 1px solid transparent;
  border-radius: 10px;
  padding: .7rem 1.2rem;
  cursor: pointer;
  transition: background .15s, border-color .15s, color .15s, transform .05s;
}
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--primary-hover); }
.btn-secondary { background: var(--surface-2); color: var(--text); border-color: var(--border); }
.btn-secondary:hover:not(:disabled) { border-color: var(--primary); }
.btn-ghost { background: transparent; color: var(--muted); border-color: var(--border); }
.btn-ghost:hover { color: var(--text); }
.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover { filter: brightness(1.08); }
.btn-sm { padding: .4rem .75rem; font-size: .85rem; }
.btn-block { width: 100%; }

/* Inicio */
#screen-start.active {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px 16px;
}
.start-card { max-width: 620px; width: 100%; padding: 2.5rem 2rem; }
.eyebrow {
  margin: 0 0 .5rem;
  font-size: .8rem;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--primary);
}
h1 { font-size: clamp(1.6rem, 4vw, 2.2rem); }
.tm { color: var(--muted); font-weight: 500; }
.lead { color: var(--muted); margin: .5rem 0 1.5rem; }
.mode-select { display: grid; grid-template-columns: 1fr 1fr; gap: .75rem; margin: 0 0 1.25rem; }
.mode-option {
  font: inherit;
  text-align: left;
  color: var(--text);
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: 12px;
  padding: .9rem 1rem;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: .25rem;
  transition: border-color .15s, background .15s;
}
.mode-option:hover { border-color: var(--primary); }
.mode-option:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }
.mode-option.active { border-color: var(--primary); background: var(--primary-soft); }
.mode-title { font-weight: 700; }
.mode-desc { font-size: .82rem; color: var(--muted); }
.mode-count { font-size: .78rem; font-weight: 600; color: var(--primary); margin-top: .2rem; }
.result-mode { margin: 0 0 -.5rem; font-size: .85rem; }
.facts {
  list-style: none;
  padding: 0;
  margin: 0 0 1.5rem;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: .75rem;
}
.facts li {
  background: var(--surface-2);
  border-radius: 12px;
  padding: 1rem .5rem;
  text-align: center;
  display: flex;
  flex-direction: column;
}
.facts strong { font-size: 1.6rem; color: var(--primary); }
.facts span { font-size: .8rem; color: var(--muted); }
.rules { padding-left: 1.2rem; margin: 0 0 1.5rem; color: var(--muted); }
.rules li { margin-bottom: .3rem; }
.note {
  background: var(--warning-soft);
  color: var(--text);
  border-left: 3px solid var(--warning);
  padding: .75rem 1rem;
  border-radius: 8px;
  font-size: .9rem;
}
.start-actions { display: flex; gap: .75rem; flex-wrap: wrap; justify-content: flex-end; }

/* Barra del examen */
.exam-bar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.exam-bar-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: .75rem 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.progress-info { display: flex; flex-direction: column; font-size: .9rem; font-weight: 600; }
.progress-info .muted { font-weight: 400; font-size: .8rem; }
.timer {
  font-variant-numeric: tabular-nums;
  font-size: 1.4rem;
  font-weight: 700;
  padding: .3rem .9rem;
  border-radius: 10px;
  background: var(--primary-soft);
  color: var(--primary);
}
.timer.warning { background: var(--warning-soft); color: var(--warning); }
.timer.critical { background: var(--danger-soft); color: var(--danger); animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: .6; } }
#btn-toggle-nav { display: none; }
.progress { height: 4px; background: var(--surface-2); }
.progress-fill { height: 100%; width: 0; background: var(--primary); transition: width .25s; }

.exam-layout {
  max-width: 1100px;
  margin: 0 auto;
  padding: 24px 16px 48px;
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 24px;
  align-items: start;
}
.question-card { padding: 1.75rem; }
.question-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 1rem; gap: .5rem; }
.q-badge {
  background: var(--primary-soft);
  color: var(--primary);
  font-weight: 700;
  border-radius: 8px;
  padding: .25rem .7rem;
  font-size: .9rem;
}
.flag-btn[aria-pressed="true"] { background: var(--warning-soft); color: var(--warning); border-color: var(--warning); }
.q-text { font-size: 1.05rem; font-weight: 500; margin: 0 0 1.5rem; }

.options { display: flex; flex-direction: column; gap: .75rem; }
.option {
  display: flex;
  gap: .9rem;
  align-items: flex-start;
  text-align: left;
  width: 100%;
  font: inherit;
  color: var(--text);
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: 12px;
  padding: .9rem 1rem;
  cursor: pointer;
  transition: border-color .15s, background .15s;
}
.option:hover { border-color: var(--primary); }
.option:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }
.option.selected { border-color: var(--primary); background: var(--primary-soft); }
.option-letter {
  flex: 0 0 auto;
  width: 30px;
  height: 30px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-weight: 700;
  font-size: .9rem;
  background: var(--surface-2);
  color: var(--muted);
}
.option.selected .option-letter { background: var(--primary); color: #fff; }
.option-text { padding-top: 3px; }

.question-nav { display: flex; justify-content: space-between; gap: .75rem; margin-top: 1.75rem; }

.nav-panel { padding: 1.25rem; position: sticky; top: 96px; }
.nav-panel h2 { font-size: 1rem; margin-bottom: 1rem; }
.nav-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: 6px; margin-bottom: 1rem; }
.nav-item {
  font: inherit;
  font-size: .85rem;
  font-weight: 600;
  aspect-ratio: 1;
  border-radius: 8px;
  border: 1.5px solid var(--border);
  background: var(--surface);
  color: var(--muted);
  cursor: pointer;
  position: relative;
}
.nav-item.answered { background: var(--primary); border-color: var(--primary); color: #fff; }
.nav-item.flagged::after {
  content: "";
  position: absolute;
  top: 3px;
  right: 3px;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--warning);
}
.nav-item.current { outline: 2px solid var(--text); outline-offset: 1px; }
.legend { list-style: none; padding: 0; margin: 0 0 1.25rem; font-size: .8rem; color: var(--muted); display: flex; flex-wrap: wrap; gap: .4rem 1rem; }
.legend li { display: flex; align-items: center; gap: .4rem; }
.dot { width: 12px; height: 12px; border-radius: 4px; display: inline-block; }
.dot-answered { background: var(--primary); }
.dot-flagged { background: var(--warning); border-radius: 50%; }
.dot-empty { border: 1.5px solid var(--border); }

/* Resultados */
.results-layout {
  max-width: 1100px;
  margin: 0 auto;
  padding: 24px 16px 48px;
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 24px;
  align-items: start;
}
.result-summary {
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
  position: sticky;
  top: 24px;
}
.result-badge {
  font-weight: 700;
  font-size: 1.1rem;
  padding: .5rem 1.25rem;
  border-radius: 999px;
}
.result-badge.pass { background: var(--success-soft); color: var(--success); }
.result-badge.fail { background: var(--danger-soft); color: var(--danger); }
.score-ring { position: relative; width: 160px; height: 160px; }
.score-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.ring-bg { fill: none; stroke: var(--surface-2); stroke-width: 10; }
.ring-fg { fill: none; stroke-width: 10; stroke-linecap: round; transition: stroke-dashoffset 1s ease; }
.ring-fg.pass { stroke: var(--success); }
.ring-fg.fail { stroke: var(--danger); }
.score-text {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}
.score-text strong { font-size: 2rem; }
.score-text span { color: var(--muted); font-size: .9rem; }
.stats { list-style: none; padding: 0; margin: 0; width: 100%; display: grid; grid-template-columns: 1fr 1fr; gap: .5rem; }
.stats li { background: var(--surface-2); border-radius: 10px; padding: .6rem; text-align: center; display: flex; flex-direction: column; }
.stats strong { font-size: 1.2rem; font-variant-numeric: tabular-nums; }
.stats span { font-size: .75rem; color: var(--muted); }
#pass-line { margin: 0; font-size: .85rem; }
.module-breakdown { width: 100%; }
.module-breakdown h3 { font-size: .85rem; margin: 0 0 .6rem; color: var(--muted); font-weight: 600; }
.mod-row { display: grid; grid-template-columns: 74px 1fr 44px; align-items: center; gap: .6rem; font-size: .85rem; margin-bottom: .45rem; }
.mod-row b { text-align: right; font-variant-numeric: tabular-nums; }
.mod-bar { height: 8px; border-radius: 99px; background: var(--surface-2); overflow: hidden; }
.mod-bar span { display: block; height: 100%; border-radius: 99px; }
.mod-bar .pass { background: var(--success); }
.mod-bar .fail { background: var(--danger); }

.tabs { display: flex; gap: .5rem; margin-bottom: 1rem; flex-wrap: wrap; }
.tab {
  font: inherit;
  font-weight: 600;
  font-size: .9rem;
  padding: .5rem 1rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--muted);
  cursor: pointer;
}
.tab.active { background: var(--primary); border-color: var(--primary); color: #fff; }
.tab span { opacity: .8; font-weight: 500; }

.review-list { display: flex; flex-direction: column; gap: 1rem; }
.review-item { padding: 1.25rem 1.5rem; border-left: 4px solid var(--border); }
.review-item.correct { border-left-color: var(--success); }
.review-item.wrong { border-left-color: var(--danger); }
.review-head { display: flex; justify-content: space-between; align-items: center; gap: .5rem; margin-bottom: .6rem; }
.review-head .num { font-weight: 700; color: var(--muted); font-size: .85rem; }
.status-pill { font-size: .75rem; font-weight: 700; padding: .2rem .65rem; border-radius: 999px; }
.status-pill.correct { background: var(--success-soft); color: var(--success); }
.status-pill.wrong { background: var(--danger-soft); color: var(--danger); }
.review-q { font-weight: 500; margin: 0 0 .9rem; }
.review-options { list-style: none; padding: 0; margin: 0 0 .9rem; display: flex; flex-direction: column; gap: .4rem; }
.review-options li {
  display: flex;
  gap: .6rem;
  padding: .55rem .75rem;
  border-radius: 8px;
  font-size: .92rem;
  border: 1px solid transparent;
}
.review-options li b { flex: 0 0 auto; }
.review-options li.is-correct { background: var(--success-soft); border-color: var(--success); }
.review-options li.is-chosen-wrong { background: var(--danger-soft); border-color: var(--danger); }
.review-options .tag { margin-left: auto; flex: 0 0 auto; font-size: .72rem; font-weight: 700; white-space: nowrap; padding-left: .5rem; }
.review-options .is-correct .tag { color: var(--success); }
.review-options .is-chosen-wrong .tag { color: var(--danger); }
.review-item:not(.revealed) .reveal-only { display: none; }
.review-item.revealed .review-options li.is-answer { background: var(--success-soft); border-color: var(--success); }
.review-options .is-answer .tag { color: var(--success); }
.reveal-btn { margin-bottom: .9rem; }
.answer-line { margin: 0 0 .6rem; color: var(--text); }
.explanation {
  background: var(--surface-2);
  border-radius: 8px;
  padding: .75rem 1rem;
  font-size: .9rem;
  color: var(--muted);
}
.explanation strong { color: var(--text); }
.empty-state { padding: 2rem; text-align: center; color: var(--muted); }

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(10, 15, 30, .55);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  z-index: 50;
}
.modal[hidden] { display: none; }
.modal-box { max-width: 440px; width: 100%; padding: 1.75rem; }
.modal-box h2 { font-size: 1.2rem; margin-bottom: .75rem; }
.modal-box p { color: var(--muted); margin: 0 0 1.5rem; }
.modal-actions { display: flex; gap: .75rem; justify-content: flex-end; flex-wrap: wrap; }

/* Responsivo */
@media (max-width: 900px) {
  .exam-layout { grid-template-columns: 1fr; }
  #btn-toggle-nav { display: inline-block; }
  .nav-panel { display: none; position: static; order: -1; }
  .nav-panel.open { display: block; }
  .nav-grid { grid-template-columns: repeat(8, 1fr); }
  .results-layout { grid-template-columns: 1fr; }
  .result-summary { position: static; }
}

@media (max-width: 560px) {
  .start-card { padding: 1.75rem 1.25rem; }
  .facts strong { font-size: 1.3rem; }
  .mode-select { grid-template-columns: 1fr; }
  .start-actions .btn { width: 100%; }
  .exam-bar-inner { gap: .5rem; }
  .timer { font-size: 1.15rem; padding: .25rem .6rem; }
  .question-card { padding: 1.25rem; }
  .q-text { font-size: 1rem; }
  .option { padding: .8rem; gap: .7rem; }
  .question-nav .btn { flex: 1; }
  .nav-grid { grid-template-columns: repeat(6, 1fr); }
  .review-item { padding: 1rem; }
  .review-options li { display: grid; grid-template-columns: auto 1fr; }
  .review-options .tag { grid-column: 2; margin-left: 0; padding-left: 0; }
  .modal-actions .btn { width: 100%; }
}