/* ─── Variables ─────────────────────────────────────────────── */
:root {
  --bg: #fafaf8;
  --bg-card: #ffffff;
  --text: #1a1a1a;
  --text-muted: #6b7280;
  --accent: #4f46e5;
  --accent-hover: #4338ca;
  --border: #e5e7eb;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-card-hover: 0 4px 12px rgba(0,0,0,0.10), 0 2px 4px rgba(0,0,0,0.06);
  --radius: 10px;
  --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --transition: 150ms ease;
  --max-w: 640px;
  --max-w-article: 680px;
}

/* ─── Reset ─────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ─── Screens ───────────────────────────────────────────────── */
.screen { display: none; min-height: 100vh; }
.screen.active { display: flex; flex-direction: column; }

/* ─── Header: Home ──────────────────────────────────────────── */
.header {
  text-align: center;
  padding: 3.5rem 1.5rem 2rem;
}
.logo {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--accent);
}
.tagline {
  margin-top: 0.4rem;
  color: var(--text-muted);
  font-size: 0.95rem;
}

/* ─── Header: Nav screens ───────────────────────────────────── */
.header-nav {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: var(--bg);
  z-index: 10;
}
.back-btn {
  background: none;
  border: none;
  color: var(--accent);
  font-size: 0.95rem;
  font-family: var(--font);
  cursor: pointer;
  padding: 0.25rem 0.5rem;
  border-radius: 6px;
  transition: background var(--transition), color var(--transition);
  white-space: nowrap;
}
.back-btn:hover { background: #ede9fe; }
.breadcrumb {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* ─── Main content wrapper ──────────────────────────────────── */
main {
  flex: 1;
  width: 100%;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 1.5rem 1.5rem 3rem;
}
#screen-article main { max-width: var(--max-w-article); }

/* ─── Prompt text ───────────────────────────────────────────── */
.prompt {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
  font-size: 0.95rem;
}

/* ─── Screen heading ────────────────────────────────────────── */
.screen-heading {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
  line-height: 1.25;
}

/* ─── Discipline Grid ───────────────────────────────────────── */
.disciplines-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}
.discipline-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem 1.25rem;
  cursor: pointer;
  transition: box-shadow var(--transition), transform var(--transition), border-color var(--transition);
  box-shadow: var(--shadow-card);
  user-select: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.discipline-card:hover {
  box-shadow: var(--shadow-card-hover);
  border-color: var(--accent);
  transform: translateY(-2px);
}
.discipline-card:active { transform: translateY(0); }
.discipline-name {
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.3;
}
.discipline-tag {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ─── Topics List ───────────────────────────────────────────── */
.topics-list {
  display: flex;
  flex-direction: column;
  gap: 0.875rem;
}
.topic-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  cursor: pointer;
  transition: box-shadow var(--transition), transform var(--transition), border-color var(--transition);
  box-shadow: var(--shadow-card);
  user-select: none;
}
.topic-card:hover {
  box-shadow: var(--shadow-card-hover);
  border-color: var(--accent);
  transform: translateY(-2px);
}
.topic-card:active { transform: translateY(0); }
.topic-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.35rem;
  line-height: 1.35;
}
.topic-teaser {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.5;
}

/* ─── Article ───────────────────────────────────────────────── */
.article-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
}
.meta-tag {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  background: #ede9fe;
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
}
.meta-time {
  font-size: 0.82rem;
  color: var(--text-muted);
}
.article-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.25;
  margin-bottom: 1.75rem;
}
.article-body {
  font-size: 1.05rem;
  line-height: 1.8;
  color: #2d2d2d;
}
.article-body p { margin-bottom: 1.25em; }
.article-body h2 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-top: 2em;
  margin-bottom: 0.6em;
  letter-spacing: -0.01em;
  color: var(--text);
}

/* ─── Sources ───────────────────────────────────────────────── */
.sources-section {
  margin-top: 2.5rem;
  border-top: 1px solid var(--border);
  padding-top: 1.25rem;
}
.sources-toggle {
  background: none;
  border: none;
  font-family: var(--font);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: color var(--transition);
}
.sources-toggle:hover { color: var(--text); }
.sources-toggle .chevron {
  display: inline-block;
  transition: transform var(--transition);
  font-style: normal;
}
.sources-toggle.open .chevron { transform: rotate(90deg); }
.sources-list {
  display: none;
  margin-top: 1rem;
  padding-left: 0;
  list-style: none;
}
.sources-list.visible { display: block; }
.sources-list li {
  font-size: 0.85rem;
  color: var(--text-muted);
  padding: 0.4rem 0;
  border-bottom: 1px solid var(--border);
  line-height: 1.5;
}
.sources-list li:last-child { border-bottom: none; }
.sources-list a {
  color: var(--accent);
  text-decoration: none;
}
.sources-list a:hover { text-decoration: underline; }
.sources-notice {
  margin-top: 0.75rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  font-style: italic;
}

/* ─── Learn More button ─────────────────────────────────────── */
.learn-more-section { margin-top: 2.5rem; }
.btn-learn-more {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  padding: 0.75rem 1.5rem;
  font-size: 0.95rem;
  font-family: var(--font);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition);
}
.btn-learn-more:hover { background: var(--accent-hover); transform: translateY(-1px); }
.btn-learn-more:active { transform: translateY(0); }
.btn-learn-more:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

/* ─── Loading: ship animation ───────────────────────────────── */
.ship-loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 3.5rem 1rem;
  gap: 0.5rem;
}
.ship-icon {
  font-size: 2rem;
  animation: ship-bob 2.4s ease-in-out infinite;
  display: block;
  filter: grayscale(100%);
}
.ship-waves {
  display: flex;
  gap: 0.1rem;
}
.ship-waves span {
  font-size: 1rem;
  color: var(--text-muted);
  display: inline-block;
  animation: wave-pulse 1.6s ease-in-out infinite;
}
.ship-waves span:nth-child(1) { animation-delay: 0s; }
.ship-waves span:nth-child(2) { animation-delay: 0.15s; }
.ship-waves span:nth-child(3) { animation-delay: 0.3s; }
.ship-waves span:nth-child(4) { animation-delay: 0.45s; }
.ship-waves span:nth-child(5) { animation-delay: 0.6s; }
@keyframes ship-bob {
  0%, 100% { transform: translateY(0) rotate(-3deg); }
  50% { transform: translateY(-7px) rotate(3deg); }
}
@keyframes wave-pulse {
  0%, 100% { opacity: 0.2; transform: translateY(0); }
  50% { opacity: 0.6; transform: translateY(-2px); }
}

/* ─── Error state ───────────────────────────────────────────── */
.error-box {
  text-align: center;
  padding: 2.5rem 1rem;
  color: var(--text-muted);
}
.error-box p { margin-bottom: 1rem; }
.btn-retry {
  background: none;
  border: 1.5px solid var(--accent);
  color: var(--accent);
  border-radius: var(--radius);
  padding: 0.6rem 1.25rem;
  font-size: 0.9rem;
  font-family: var(--font);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition), color var(--transition);
}
.btn-retry:hover { background: var(--accent); color: #fff; }

/* ─── Bookmark button (in article meta) ────────────────────── */
.btn-bookmark {
  margin-left: auto;
  background: none;
  border: 1.5px solid var(--border);
  border-radius: 6px;
  padding: 0.2rem 0.65rem;
  font-size: 0.8rem;
  font-family: var(--font);
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  transition: border-color var(--transition), color var(--transition), background var(--transition);
  white-space: nowrap;
}
.btn-bookmark:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.btn-bookmark.bookmarked {
  border-color: var(--accent);
  color: var(--accent);
  background: #ede9fe;
}

/* ─── Saved topics section (disciplines screen) ─────────────── */
.bookmarks-section {
  margin-bottom: 1.75rem;
}
.bookmarks-label {
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--text-muted);
  margin-bottom: 0.6rem;
}
.bookmarks-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.bookmark-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  transition: box-shadow var(--transition), border-color var(--transition);
  box-shadow: var(--shadow-card);
  user-select: none;
}
.bookmark-card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-card-hover);
}
.bookmark-info {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  min-width: 0;
}
.bookmark-discipline {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent);
}
.bookmark-title {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.bookmark-remove {
  margin-left: auto;
  flex-shrink: 0;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.9rem;
  cursor: pointer;
  padding: 0.25rem 0.4rem;
  border-radius: 4px;
  line-height: 1;
  transition: color var(--transition), background var(--transition);
}
.bookmark-remove:hover {
  color: #dc2626;
  background: #fee2e2;
}

/* ─── Login Screen ──────────────────────────────────────────── */
#login-screen {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 1.5rem;
}
.login-card {
  width: 100%;
  max-width: 360px;
  text-align: center;
}
.login-card .logo { margin-bottom: 0.4rem; }
.login-card .tagline { margin-bottom: 2rem; }
#login-form {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}
#login-password {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  font-size: 1rem;
  font-family: var(--font);
  background: var(--bg-card);
  color: var(--text);
  outline: none;
  transition: border-color var(--transition);
}
#login-password:focus { border-color: var(--accent); }
.btn-login {
  width: 100%;
  padding: 0.75rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-family: var(--font);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition);
}
.btn-login:hover { background: var(--accent-hover); }
.login-error {
  font-size: 0.85rem;
  color: #dc2626;
  min-height: 1.2em;
  text-align: left;
}

/* ─── Mobile ────────────────────────────────────────────────── */
@media (max-width: 600px) {
  .header { padding: 2.5rem 1rem 1.5rem; }
  main { padding: 1.25rem 1rem 2.5rem; }
  .disciplines-grid { grid-template-columns: 1fr; }
  .discipline-card { padding: 1.25rem 1rem; }
  .article-title { font-size: 1.4rem; }
  .article-body { font-size: 1rem; }
  .btn-learn-more, .btn-retry { width: 100%; justify-content: center; }
}