:root {
  --bg: #f6f0e6;
  --bg-strong: #efe3d1;
  --ink: #1b252c;
  --ink-soft: #4a5a63;
  --accent: #1c4b5f;
  --accent-2: #e15b3f;
  --accent-3: #f4c95d;
  --line: rgba(27, 37, 44, 0.14);
  --glass: rgba(255, 255, 255, 0.72);
  --shadow: 0 20px 50px rgba(19, 31, 38, 0.12);
  --radius-lg: 24px;
  --radius-md: 16px;
  --radius-sm: 12px;
  --font-display: "Bricolage Grotesque", "Trebuchet MS", sans-serif;
  --font-body: "Spectral", "Georgia", serif;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  font-family: var(--font-body);
  color: var(--ink);
  background: var(--bg);
  min-height: 100%;
}

body {
  position: relative;
  overflow-x: hidden;
}

.bg {
  position: fixed;
  inset: 0;
  z-index: -2;
  background: radial-gradient(circle at top left, #fff4dc 0%, #f6f0e6 45%, #f2e6d2 100%);
}

.grid {
  position: absolute;
  inset: 0;
  background-image: linear-gradient(rgba(27, 37, 44, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(27, 37, 44, 0.06) 1px, transparent 1px);
  background-size: 120px 120px;
  opacity: 0.4;
}

.orb {
  position: absolute;
  width: 42vw;
  height: 42vw;
  border-radius: 50%;
  filter: blur(0px);
  opacity: 0.55;
  mix-blend-mode: multiply;
}

.orb-a {
  background: radial-gradient(circle, rgba(28, 75, 95, 0.45), transparent 65%);
  top: -10vw;
  left: -12vw;
}

.orb-b {
  background: radial-gradient(circle, rgba(225, 91, 63, 0.45), transparent 65%);
  bottom: -12vw;
  right: -10vw;
}

#pulse-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 18px 6vw;
  backdrop-filter: blur(8px);
  background: rgba(246, 240, 230, 0.9);
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 16px;
  font-family: var(--font-display);
}

.logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.brand-title {
  font-weight: 700;
  font-size: 1.05rem;
}

.brand-sub {
  font-size: 0.85rem;
  color: var(--ink-soft);
}

.controls {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.topic-select {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-display);
  font-size: 0.85rem;
  color: var(--ink);
  background: rgba(255, 255, 255, 0.85);
  border: 1px solid var(--line);
  padding: 6px 12px;
  border-radius: 999px;
}

.topic-select select {
  border: none;
  background: transparent;
  font-family: var(--font-display);
  font-size: 0.9rem;
  color: var(--ink);
}

.topic-select select:focus-visible {
  outline: none;
}

button {
  font-family: var(--font-display);
  border: none;
  cursor: pointer;
  padding: 10px 16px;
  border-radius: 999px;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

button:focus-visible {
  outline: 2px solid var(--accent-2);
  outline-offset: 2px;
}

button.ghost {
  background: rgba(255, 255, 255, 0.85);
  color: var(--ink);
  border: 1px solid var(--line);
}

button.solid {
  background: var(--accent);
  color: #fff;
  box-shadow: var(--shadow);
}

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

.app {
  padding: 40px 6vw 80px;
  display: flex;
  flex-direction: column;
  gap: 40px;
}

section {
  background: var(--glass);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

section.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.section-title {
  font-family: var(--font-display);
  font-size: 1.6rem;
  margin: 0 0 12px;
}

.section-sub {
  color: var(--ink-soft);
  margin-bottom: 20px;
}

.hero {
  position: relative;
  overflow: hidden;
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(0, 0.8fr);
  gap: 24px;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(2.2rem, 3.6vw, 3.5rem);
  margin: 0 0 12px;
}

.hero p {
  font-size: 1.05rem;
  line-height: 1.6;
}

.hero .hero-badges {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 16px;
}

.badge {
  background: rgba(28, 75, 95, 0.1);
  color: var(--accent);
  padding: 8px 12px;
  border-radius: 999px;
  font-family: var(--font-display);
  font-size: 0.85rem;
}

.hero-panel {
  background: #fff;
  border-radius: var(--radius-md);
  padding: 20px;
  border: 1px dashed var(--line);
}

.hero-panel h3 {
  font-family: var(--font-display);
  margin-top: 0;
}

.grid-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 16px;
}

.card {
  padding: 16px;
  border-radius: var(--radius-md);
  background: #fff;
  border: 1px solid var(--line);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 40px rgba(19, 31, 38, 0.12);
}

.card h4 {
  margin: 0 0 8px;
  font-family: var(--font-display);
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.chip {
  padding: 8px 12px;
  border-radius: 999px;
  background: rgba(244, 201, 93, 0.3);
  border: 1px solid rgba(244, 201, 93, 0.7);
  font-family: var(--font-display);
  font-size: 0.85rem;
}

.columns {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 16px;
}

.compare-toggle {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.compare-toggle button.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.compare-card {
  background: #fff;
  border-radius: var(--radius-md);
  padding: 16px;
  border: 1px solid var(--line);
  position: relative;
}

.compare-card.active {
  border-color: var(--accent-2);
  box-shadow: 0 0 0 2px rgba(225, 91, 63, 0.2);
}

.timeline {
  display: grid;
  gap: 16px;
}

.timeline-item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 16px;
  align-items: start;
}

.timeline-dot {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent-2);
  margin-top: 6px;
}

.timeline-content {
  background: #fff;
  border-radius: var(--radius-md);
  padding: 16px;
  border: 1px solid var(--line);
}

.stack {
  display: grid;
  gap: 12px;
}

.stack-layer {
  padding: 16px;
  border-radius: var(--radius-md);
  border: 1px solid var(--line);
  background: #fff;
}

.stack-layer h4 {
  margin: 0 0 8px;
  font-family: var(--font-display);
}

.tabs {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.tab-button {
  background: rgba(28, 75, 95, 0.1);
  color: var(--accent);
  border: 1px solid rgba(28, 75, 95, 0.2);
}

.tab-button.active {
  background: var(--accent);
  color: #fff;
}

.tab-panel {
  display: none;
  background: #fff;
  border-radius: var(--radius-md);
  padding: 16px;
  border: 1px solid var(--line);
}

.tab-panel.active {
  display: block;
}

.quiz {
  display: grid;
  gap: 16px;
}

.quiz-item {
  padding: 16px;
  border-radius: var(--radius-md);
  background: #fff;
  border: 1px solid var(--line);
}

.quiz-options {
  display: grid;
  gap: 8px;
  margin-top: 12px;
}

.quiz-option {
  padding: 10px 12px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: rgba(28, 75, 95, 0.06);
  cursor: pointer;
}

.quiz-option.correct {
  border-color: rgba(28, 75, 95, 0.7);
  background: rgba(28, 75, 95, 0.12);
}

.quiz-option.wrong {
  border-color: rgba(225, 91, 63, 0.6);
  background: rgba(225, 91, 63, 0.1);
}

.quiz-feedback {
  margin-top: 8px;
  font-size: 0.9rem;
  color: var(--ink-soft);
}

.accordion {
  display: grid;
  gap: 12px;
}

.accordion details {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  padding: 12px 16px;
}

.accordion summary {
  font-family: var(--font-display);
  font-weight: 600;
  cursor: pointer;
  list-style: none;
}

.accordion summary::-webkit-details-marker {
  display: none;
}

.accordion summary::after {
  content: "＋";
  float: right;
  font-weight: 700;
}

.accordion details[open] summary::after {
  content: "－";
}

.accordion-body {
  padding-top: 10px;
  color: var(--ink-soft);
}

.loading {
  text-align: center;
  display: grid;
  place-items: center;
  gap: 12px;
}

.spinner {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: 3px solid rgba(28, 75, 95, 0.2);
  border-top-color: var(--accent);
  animation: spin 1s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.footer {
  padding: 32px 6vw 50px;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.footer-meta {
  margin-top: 6px;
  font-family: var(--font-display);
}

.hidden {
  display: none !important;
}

@media (max-width: 900px) {
  .hero {
    grid-template-columns: 1fr;
  }

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

@media (prefers-reduced-motion: reduce) {
  section {
    transition: none;
  }

  button {
    transition: none;
  }
}

body.focus-mode section {
  box-shadow: none;
}

body.focus-mode .bg,
body.focus-mode #pulse-canvas,
body.focus-mode .orb,
body.focus-mode .grid {
  display: none;
}