:root {
  --ink: #0e1116;
  --panel: #161b24;
  --panel-2: #1d2430;
  --line: rgba(197, 205, 216, 0.14);
  --mist: #c5cdd8;
  --muted: #8b96a8;
  --signal: #e8a317;
  --signal-dim: rgba(232, 163, 23, 0.16);
  --ok: #3faf78;
  --bad: #e25b4c;
  --info: #5b8def;
  --radius: 14px;
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.35);
  --font-display: "Archivo", system-ui, sans-serif;
  --font-body: "Figtree", system-ui, sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-body);
  color: var(--mist);
  background: var(--ink);
  line-height: 1.55;
  overflow-x: hidden;
}

.bg-grid {
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(197, 205, 216, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(197, 205, 216, 0.04) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse at center, black 20%, transparent 75%);
  pointer-events: none;
  z-index: 0;
}

.bg-glow {
  position: fixed;
  width: 55vw;
  height: 55vw;
  top: -18vw;
  right: -12vw;
  background: radial-gradient(circle, rgba(232, 163, 23, 0.18), transparent 65%);
  filter: blur(8px);
  pointer-events: none;
  z-index: 0;
  animation: drift 14s ease-in-out infinite alternate;
}

@keyframes drift {
  from { transform: translate(0, 0) scale(1); }
  to { transform: translate(-4%, 6%) scale(1.08); }
}

.topbar,
.app,
.site-footer {
  position: relative;
  z-index: 1;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--line);
  background: rgba(14, 17, 22, 0.82);
  backdrop-filter: blur(12px);
  position: sticky;
  top: 0;
  z-index: 20;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: inherit;
}

.brand-mark {
  width: 2.15rem;
  height: 2.15rem;
  border-radius: 8px;
  background:
    linear-gradient(135deg, var(--signal), #f0c45a 45%, transparent 46%),
    linear-gradient(315deg, #2a3344, #12161e);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.08);
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.15;
}

.brand-text strong {
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.02em;
  font-size: 1.05rem;
}

.brand-text small {
  color: var(--muted);
  font-size: 0.78rem;
}

.nav {
  display: flex;
  gap: 0.35rem;
}

.nav a {
  color: var(--muted);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.92rem;
  padding: 0.45rem 0.8rem;
  border-radius: 999px;
  transition: color 0.2s, background 0.2s;
}

.nav a:hover,
.nav a.active {
  color: var(--ink);
  background: var(--signal);
}

.nav-toggle {
  display: none;
  width: 2.4rem;
  height: 2.4rem;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--panel);
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  width: 1rem;
  height: 2px;
  margin: 0.28rem auto;
  background: var(--mist);
}

.app {
  width: min(1080px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 1.75rem 0 3.5rem;
  min-height: 70vh;
}

.site-footer {
  width: min(1080px, calc(100% - 2rem));
  margin: 0 auto 2rem;
  color: var(--muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

.hero {
  display: grid;
  gap: 1.5rem;
  padding: 2.2rem 0 1rem;
  animation: rise 0.55s ease both;
}

@keyframes rise {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: none; }
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  color: var(--signal);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.75rem;
}

.hero h1 {
  margin: 0.35rem 0 0.6rem;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  letter-spacing: -0.035em;
  line-height: 1.05;
  color: #f3f5f8;
}

.hero h1 span {
  color: var(--signal);
}

.lead {
  margin: 0;
  max-width: 38rem;
  font-size: 1.08rem;
  color: var(--muted);
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin-top: 0.4rem;
}

.btn {
  appearance: none;
  border: 1px solid transparent;
  border-radius: 999px;
  padding: 0.75rem 1.2rem;
  font: inherit;
  font-weight: 700;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  transition: transform 0.15s ease, background 0.2s, border-color 0.2s, color 0.2s;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: var(--signal);
  color: var(--ink);
}

.btn-primary:hover {
  background: #f0b73a;
}

.btn-ghost {
  background: transparent;
  border-color: var(--line);
  color: var(--mist);
}

.btn-ghost:hover {
  border-color: var(--signal);
  color: var(--signal);
}

.stats {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
  margin-top: 1.2rem;
}

.stat {
  background: linear-gradient(180deg, var(--panel-2), var(--panel));
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
}

.stat strong {
  display: block;
  font-family: var(--font-display);
  font-size: 1.55rem;
  color: #fff;
  letter-spacing: -0.03em;
}

.stat span {
  color: var(--muted);
  font-size: 0.88rem;
}

.section-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 1rem;
  margin: 2rem 0 1rem;
}

.section-head h2 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 1.45rem;
  letter-spacing: -0.02em;
  color: #fff;
}

.section-head p {
  margin: 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.module-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 0.85rem;
}

.module-card {
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  padding: 1.1rem 1.15rem;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: rgba(22, 27, 36, 0.9);
  text-decoration: none;
  color: inherit;
  transition: border-color 0.2s, transform 0.2s, background 0.2s;
  min-height: 150px;
}

.module-card:hover {
  border-color: rgba(232, 163, 23, 0.55);
  transform: translateY(-2px);
  background: var(--panel-2);
}

.module-card .meta {
  display: flex;
  justify-content: space-between;
  gap: 0.5rem;
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 600;
}

.module-card .num {
  color: var(--signal);
  font-family: var(--font-display);
  font-weight: 800;
}

.module-card h3 {
  margin: 0;
  font-size: 1.08rem;
  color: #fff;
  letter-spacing: -0.01em;
}

.module-card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
  flex: 1;
}

.progress-bar {
  height: 6px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.06);
  overflow: hidden;
}

.progress-bar > i {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--signal), #f0c45a);
  border-radius: inherit;
  transition: width 0.45s ease;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: calc(var(--radius) + 2px);
  padding: 1.25rem;
  box-shadow: var(--shadow);
  animation: rise 0.4s ease both;
}

.panel + .panel {
  margin-top: 1rem;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--muted);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 0.85rem;
}

.back-link:hover {
  color: var(--signal);
}

.kicker {
  color: var(--signal);
  font-weight: 700;
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.page-title {
  margin: 0.2rem 0 0.5rem;
  font-family: var(--font-display);
  font-size: clamp(1.7rem, 3.5vw, 2.35rem);
  letter-spacing: -0.03em;
  color: #fff;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin: 1rem 0 0.25rem;
}

.retain-list,
.note-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0.65rem;
}

.retain-list li,
.note-list li {
  padding: 0.85rem 1rem;
  border-left: 3px solid var(--signal);
  background: var(--signal-dim);
  border-radius: 0 12px 12px 0;
}

.note-list li {
  border-left-color: var(--info);
  background: rgba(91, 141, 239, 0.1);
}

.note-list strong {
  display: block;
  color: #fff;
  margin-bottom: 0.2rem;
}

.flash-wrap {
  perspective: 1200px;
  min-height: 240px;
}

.flashcard {
  position: relative;
  width: 100%;
  min-height: 240px;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(0.2, 0.8, 0.2, 1);
  cursor: pointer;
}

.flashcard.flipped {
  transform: rotateY(180deg);
}

.flash-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: linear-gradient(160deg, var(--panel-2), var(--panel));
  display: grid;
  place-items: center;
  padding: 1.5rem;
  text-align: center;
}

.flash-face.back {
  transform: rotateY(180deg);
  background: linear-gradient(160deg, #243018, #1a2214);
  border-color: rgba(63, 175, 120, 0.35);
}

.flash-face small {
  position: absolute;
  top: 1rem;
  left: 1rem;
  color: var(--muted);
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  font-size: 0.72rem;
}

.flash-face p {
  margin: 0;
  font-size: clamp(1.1rem, 2.4vw, 1.4rem);
  color: #fff;
  font-weight: 600;
  max-width: 28rem;
}

.quiz-meta {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.75rem;
  color: var(--muted);
  font-weight: 600;
  margin-bottom: 1rem;
}

.question {
  font-size: 1.2rem;
  color: #fff;
  font-weight: 700;
  margin: 0 0 1rem;
}

.choices {
  display: grid;
  gap: 0.55rem;
}

.choice {
  width: 100%;
  text-align: left;
  border: 1px solid var(--line);
  background: var(--panel-2);
  color: var(--mist);
  border-radius: 12px;
  padding: 0.9rem 1rem;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.choice:hover:not(:disabled) {
  border-color: rgba(232, 163, 23, 0.5);
}

.choice.selected {
  border-color: var(--signal);
  background: var(--signal-dim);
}

.choice.correct {
  border-color: var(--ok);
  background: rgba(63, 175, 120, 0.15);
  color: #d8f5e6;
}

.choice.wrong {
  border-color: var(--bad);
  background: rgba(226, 91, 76, 0.12);
}

.explain {
  margin-top: 1rem;
  padding: 0.9rem 1rem;
  border-radius: 12px;
  background: rgba(91, 141, 239, 0.12);
  border: 1px solid rgba(91, 141, 239, 0.28);
  color: var(--mist);
}

.result-score {
  font-family: var(--font-display);
  font-size: clamp(2.5rem, 6vw, 4rem);
  letter-spacing: -0.04em;
  color: #fff;
  margin: 0.4rem 0;
}

.result-score.pass { color: var(--ok); }
.result-score.fail { color: var(--bad); }

.empty {
  color: var(--muted);
  text-align: center;
  padding: 2rem 1rem;
}

.progress-table {
  width: 100%;
  border-collapse: collapse;
}

.progress-table th,
.progress-table td {
  text-align: left;
  padding: 0.7rem 0.4rem;
  border-bottom: 1px solid var(--line);
  font-size: 0.95rem;
}

.progress-table th {
  color: var(--muted);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.15rem 0.55rem;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
}

.badge-ok {
  background: rgba(63, 175, 120, 0.18);
  color: #7ddeb0;
}

.badge-warn {
  background: rgba(232, 163, 23, 0.18);
  color: #f0c45a;
}

.badge-muted {
  background: rgba(255, 255, 255, 0.06);
  color: var(--muted);
}

@media (max-width: 780px) {
  .nav-toggle {
    display: inline-block;
  }

  .nav {
    display: none;
    position: absolute;
    top: calc(100% + 0.35rem);
    right: 1rem;
    flex-direction: column;
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 14px;
    padding: 0.45rem;
    min-width: 12rem;
    box-shadow: var(--shadow);
  }

  .nav.open {
    display: flex;
  }

  .stats {
    grid-template-columns: 1fr;
  }

  .section-head {
    flex-direction: column;
    align-items: start;
  }
}