/* ==========================================================================
   AI Research & Technology Lab - Theme CSS
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. CSS Custom Properties - Dark Theme (default)
   -------------------------------------------------------------------------- */
:root,
[data-theme="dark"] {
  --bg: #0b1020;
  --bg-elevated: #111827;
  --bg-card: #020617;
  --fg: #e5e7eb;
  --fg-muted: #b4b4b4;
  --accent: #38bdf8;
  --accent-hover: #0ea5e9;
  --accent-soft: rgba(56, 189, 248, 0.14);
  --border-subtle: #1f2937;
  --max-width: 1120px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --shadow-soft: 0 22px 45px rgba(0, 0, 0, 0.5);

  /* Dark-specific backgrounds */
  --body-bg: radial-gradient(circle at top, #111827 0, #020617 55%);
  --header-bg: radial-gradient(circle at top left, #111827 0, rgba(15, 23, 42, 0.85) 52%, rgba(15, 23, 42, 0.6) 100%);
  --hero-left-bg: linear-gradient(145deg, rgba(15, 23, 42, 0.9), rgba(15, 23, 42, 0.7));
  --card-bg: radial-gradient(circle at top left, #1f2937 0, #020617 55%);
  --feature-card-bg: rgba(15, 23, 42, 0.96);
  --btn-secondary-bg: rgba(15, 23, 42, 0.9);
  --btn-secondary-hover-bg: rgba(15, 23, 42, 1);
  --hero-title-gradient: linear-gradient(to right, #e5e7eb, #bae6fd);
  --hero-glow-1: rgba(56, 189, 248, 0.36);
  --hero-glow-2: rgba(94, 234, 212, 0.22);
  --kicker-dot: #22c55e;
  --kicker-dot-glow: rgba(34, 197, 94, 0.9);
  --card-pill-dot: #facc15;
  --card-pill-dot-glow: rgba(250, 204, 21, 0.8);
}

/* --------------------------------------------------------------------------
   1b. Light Theme Variables
   -------------------------------------------------------------------------- */
[data-theme="light"] {
  --bg: #f8fafc;
  --bg-elevated: #ffffff;
  --bg-card: #ffffff;
  --fg: #1e293b;
  --fg-muted: #64748b;
  --accent: #0284c7;
  --accent-hover: #0369a1;
  --accent-soft: rgba(2, 132, 199, 0.1);
  --border-subtle: #e2e8f0;
  --shadow-soft: 0 22px 45px rgba(0, 0, 0, 0.08);

  /* Light-specific backgrounds */
  --body-bg: linear-gradient(to bottom, #f1f5f9 0%, #ffffff 100%);
  --header-bg: linear-gradient(to right, rgba(255, 255, 255, 0.95), rgba(248, 250, 252, 0.9));
  --hero-left-bg: linear-gradient(145deg, rgba(255, 255, 255, 0.95), rgba(248, 250, 252, 0.9));
  --card-bg: linear-gradient(145deg, #ffffff 0%, #f8fafc 100%);
  --feature-card-bg: rgba(255, 255, 255, 0.98);
  --btn-secondary-bg: rgba(248, 250, 252, 0.95);
  --btn-secondary-hover-bg: rgba(255, 255, 255, 1);
  --hero-title-gradient: linear-gradient(to right, #1e293b, #0284c7);
  --hero-glow-1: rgba(56, 189, 248, 0.15);
  --hero-glow-2: rgba(94, 234, 212, 0.1);
  --kicker-dot: #22c55e;
  --kicker-dot-glow: rgba(34, 197, 94, 0.6);
  --card-pill-dot: #f59e0b;
  --card-pill-dot-glow: rgba(245, 158, 11, 0.5);
}

/* --------------------------------------------------------------------------
   2. Base & Reset
   -------------------------------------------------------------------------- */
* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", sans-serif;
  background: var(--body-bg);
  color: var(--fg);
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
}

a {
  color: inherit;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* --------------------------------------------------------------------------
   3. Layout
   -------------------------------------------------------------------------- */
.page-wrap {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 20px 16px 64px;
}

main {
  margin-top: 26px;
}

/* --------------------------------------------------------------------------
   4. Header / Navigation
   -------------------------------------------------------------------------- */
header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 16px;
  margin-bottom: 16px;
  border-radius: 999px;
  border: 1px solid rgba(148, 163, 184, 0.2);
  background: var(--header-bg);
  backdrop-filter: blur(18px);
  position: sticky;
  top: 12px;
  z-index: 50;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
  text-decoration: none;
}

.brand:hover {
  text-decoration: none;
}

.brand-logo {
  width: 34px;
  height: 34px;
  border-radius: 10px;
  background: radial-gradient(circle at 30% 0, var(--accent) 0, var(--bg-card) 55%);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  flex-shrink: 0;
}

.brand-logo img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}

.brand-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 0;
}

.brand-name {
  font-size: 0.94rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.brand-tagline {
  font-size: 0.72rem;
  color: var(--fg-muted);
  letter-spacing: 0.09em;
  text-transform: uppercase;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

nav {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.88rem;
}

.nav-link {
  padding: 7px 12px;
  border-radius: 999px;
  color: var(--fg-muted);
  border: 1px solid transparent;
  text-decoration: none;
  transition: all 0.16s ease-out;
}

.nav-link:hover {
  color: var(--fg);
  border-color: rgba(148, 163, 184, 0.45);
  background: var(--btn-secondary-bg);
  text-decoration: none;
}

.nav-link.primary {
  color: var(--bg);
  background: var(--accent);
  border-color: transparent;
  font-weight: 500;
  box-shadow: 0 10px 25px rgba(56, 189, 248, 0.45);
}

[data-theme="light"] .nav-link.primary {
  box-shadow: 0 10px 25px rgba(2, 132, 199, 0.3);
}

.nav-link.primary:hover {
  background: var(--accent-hover);
  color: var(--bg);
  border-color: transparent;
  box-shadow: 0 14px 35px rgba(56, 189, 248, 0.6);
}

[data-theme="light"] .nav-link.primary:hover {
  box-shadow: 0 14px 35px rgba(2, 132, 199, 0.4);
}

/* --------------------------------------------------------------------------
   5. Theme Toggle Button
   -------------------------------------------------------------------------- */
.theme-toggle {
  background: transparent;
  border: 1px solid var(--border-subtle);
  border-radius: 999px;
  padding: 7px 12px;
  cursor: pointer;
  color: var(--fg-muted);
  font-size: 1rem;
  transition: all 0.16s ease-out;
  display: flex;
  align-items: center;
  justify-content: center;
}

.theme-toggle:hover {
  color: var(--fg);
  border-color: rgba(148, 163, 184, 0.45);
  background: var(--btn-secondary-bg);
}

[data-theme="dark"] .theme-icon-dark { display: none; }
[data-theme="dark"] .theme-icon-light { display: inline; }
[data-theme="light"] .theme-icon-light { display: none; }
[data-theme="light"] .theme-icon-dark { display: inline; }

/* --------------------------------------------------------------------------
   6. Hero Section
   -------------------------------------------------------------------------- */
.hero {
  display: grid;
  grid-template-columns: minmax(0, 3.5fr) minmax(0, 1.75fr);
  gap: 28px;
  align-items: stretch;
}

.hero-left {
  background: none;
  border-radius: 0;
  border: none;
  box-shadow: none;
  padding: 20px 0;
  position: relative;
  overflow: hidden;
}

.hero-left::before {
  display: none;
}

.hero-content {
  position: relative;
  z-index: 1;
}

.hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 10px 4px 5px;
  border-radius: 999px;
  background: var(--btn-secondary-bg);
  border: 1px solid rgba(148, 163, 184, 0.45);
  color: var(--fg-muted);
  font-size: 0.72rem;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  margin-bottom: 12px;
}

.hero-kicker-dot {
  width: 7px;
  height: 7px;
  border-radius: 999px;
  background: var(--kicker-dot);
  box-shadow: 0 0 14px var(--kicker-dot-glow);
}

.hero-title {
  font-size: clamp(1.9rem, 3vw, 2.4rem);
  line-height: 1.2;
  margin: 0 0 16px;
  letter-spacing: 0.02em;
}

.hero-title span {
  color: var(--fg);
}

.hero-intro {
  font-size: 1.05rem;
  color: var(--fg);
  max-width: 44rem;
  line-height: 1.6;
  margin-bottom: 14px;
}

.hero-intro strong {
  font-weight: inherit;
  color: var(--accent);
}

.hero-bold {
  font-size: 1rem;
  color: var(--fg);
  font-weight: 500;
  margin-bottom: 20px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 2px;
}

.hero-right {
  display: flex;
  align-items: stretch;
}

/* --------------------------------------------------------------------------
   7. Buttons
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 9px 16px;
  border-radius: 999px;
  font-size: 0.9rem;
  border: 1px solid transparent;
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.16s ease-out;
}

.btn-primary {
  background: var(--accent);
  color: var(--bg);
  font-weight: 600;
}

[data-theme="light"] .btn-primary {
  color: #ffffff;
}

.btn-primary:hover {
  background: var(--accent-hover);
  color: var(--bg);
  text-decoration: none;
}

[data-theme="light"] .btn-primary:hover {
  color: #ffffff;
}

.btn-secondary {
  background: var(--btn-secondary-bg);
  border-color: var(--accent);
  border-width: 1px;
  color: var(--accent);
}

.btn-secondary:hover {
  background: var(--btn-secondary-hover-bg);
  border-color: var(--accent-hover);
  color: var(--accent-hover);
  text-decoration: none;
}

.btn-ghost {
  background: var(--btn-secondary-bg);
  border-color: rgba(148, 163, 184, 0.6);
  color: var(--fg);
  font-size: 0.88rem;
  padding-inline: 14px;
}

.btn-ghost:hover {
  background: var(--btn-secondary-hover-bg);
  border-color: rgba(148, 163, 184, 0.8);
  text-decoration: none;
}

.btn .arrow {
  margin-left: 6px;
  font-size: 0.9em;
}

/* --------------------------------------------------------------------------
   8. Cards (sidebar, under construction)
   -------------------------------------------------------------------------- */
.card-under-construction {
  border-radius: var(--radius-xl);
  background: var(--card-bg);
  padding: 16px 14px 14px;
  border: 1px solid rgba(148, 163, 184, 0.4);
  box-shadow: var(--shadow-soft);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  width: 100%;
}

.card-pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--btn-secondary-bg);
  border: 1px solid rgba(148, 163, 184, 0.6);
  font-size: 0.68rem;
  color: var(--fg-muted);
  text-transform: uppercase;
  letter-spacing: 0.13em;
  margin-bottom: 10px;
}

.card-pill-dot {
  width: 8px;
  height: 8px;
  border-radius: 999px;
  background: var(--card-pill-dot);
  box-shadow: 0 0 16px var(--card-pill-dot-glow);
}

.card-title {
  font-size: 0.95rem;
  font-weight: 600;
  margin: 0 0 6px;
}

.card-body {
  font-size: 0.88rem;
  color: var(--fg-muted);
  font-style: italic;
  line-height: 1.6;
  margin-bottom: 12px;
}

.card-footer {
  display: flex;
  justify-content: flex-start;
}


/* --------------------------------------------------------------------------
   9. Section / Feature Grid
   -------------------------------------------------------------------------- */
.section {
  margin-top: 48px;
}

.section-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 20px;
}

.section-title {
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--fg-muted);
}

.section-subtitle {
  font-size: 0.8rem;
  color: var(--fg-muted);
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
}

.feature-card {
  background: var(--feature-card-bg);
  border-radius: var(--radius-lg);
  border: 1px solid rgba(148, 163, 184, 0.45);
  padding: 20px 18px 16px;
  box-shadow: 0 16px 35px rgba(15, 23, 42, 0.85);
  display: flex;
  flex-direction: column;
  gap: 8px;
  position: relative;
  overflow: hidden;
}

[data-theme="light"] .feature-card {
  box-shadow: 0 16px 35px rgba(0, 0, 0, 0.06);
}

.feature-card::before {
  content: "";
  position: absolute;
  inset: -30%;
  background:
    radial-gradient(circle at 0 0, rgba(56, 189, 248, 0.18) 0, transparent 50%),
    radial-gradient(circle at 100% 100%, rgba(94, 234, 212, 0.12) 0, transparent 55%);
  opacity: 0.6;
  pointer-events: none;
  mix-blend-mode: screen;
}

[data-theme="light"] .feature-card::before {
  mix-blend-mode: multiply;
  opacity: 0.15;
}

.feature-content {
  position: relative;
  z-index: 1;
}

.feature-label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.13em;
  color: var(--fg-muted);
  margin-bottom: 6px;
}

.feature-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 2px;
}

.feature-subtitle {
  font-size: 0.86rem;
  font-style: italic;
  color: var(--fg-muted);
  margin-bottom: 8px;
}

.feature-body {
  font-size: 0.92rem;
  color: var(--fg);
  line-height: 1.6;
}

.feature-body strong {
  font-weight: inherit;
  color: var(--accent);
}

.feature-list {
  margin: 10px 0 0;
  padding-left: 18px;
  font-size: 0.88rem;
  color: var(--fg);
}

.feature-list li {
  margin-bottom: 4px;
}

/* --------------------------------------------------------------------------
   10. Content Pages (About, Contact, AGB, Post, Collection)
   -------------------------------------------------------------------------- */
hr.section-divider {
  margin: 38px 0 28px;
  border: none;
  border-top: 1px solid rgba(55, 65, 81, 0.9);
}

[data-theme="light"] hr.section-divider {
  border-top-color: rgba(203, 213, 225, 0.9);
}

.content-page {
  margin-top: 30px;
}

.page-header {
  margin-bottom: 20px;
}

.page-title {
  font-size: 1.6rem;
  margin: 0 0 4px;
  letter-spacing: 0.02em;
}

.page-meta {
  font-size: 0.8rem;
  color: var(--fg-muted);
}

.page-content {
  background: none;
  border-radius: 0;
  border: none;
  padding: 0;
  box-shadow: none;
  font-size: 0.95rem;
  line-height: 1.7;
  max-width: 720px;
  margin: 0 auto;
}

.page-content h2 {
  font-size: 1.1rem;
  margin: 36px 0 12px;
}

.page-content h2:first-child {
  margin-top: 0;
}

.page-content p {
  margin: 0 0 16px;
  color: var(--fg);
}

.page-content p strong {
  font-weight: inherit;
  color: var(--accent);
}

.page-content ul,
.page-content ol {
  margin: 8px 0 20px 20px;
  padding: 0;
  color: var(--fg);
}

.page-content li {
  margin-bottom: 8px;
}

.page-content hr {
  margin: 32px 0 28px;
  border: none;
  border-top: 1px solid rgba(55, 65, 81, 0.9);
}

[data-theme="light"] .page-content hr {
  border-top-color: rgba(203, 213, 225, 0.9);
}

.page-content a {
  color: var(--accent);
}

.page-content a:hover {
  text-decoration: underline;
}

.page-content pre {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 16px;
  overflow-x: auto;
  font-size: 0.85rem;
  line-height: 1.5;
}

.page-content code {
  font-family: "JetBrains Mono", "Fira Code", monospace;
}

.page-cta {
  margin-top: 20px;
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

/* About section (used by about page) */
#about {
  margin-top: 50px;
  padding-top: 30px;
}

.about-header {
  margin-bottom: 16px;
}

.about-title {
  font-size: 1.6rem;
  margin: 0 0 4px;
  letter-spacing: 0.02em;
}

.about-meta {
  font-size: 0.8rem;
  color: var(--fg-muted);
}

.about-content {
  background: none;
  border-radius: 0;
  border: none;
  padding: 0;
  box-shadow: none;
  font-size: 0.95rem;
  line-height: 1.7;
}

.about-content h2 {
  font-size: 1.1rem;
  margin: 0 0 8px;
}

.about-content p {
  margin: 0 0 12px;
  color: var(--fg);
}

.about-content p strong {
  font-weight: inherit;
  color: var(--accent);
}

.about-content ul {
  margin: 4px 0 14px 20px;
  padding: 0;
  color: var(--fg);
}

.about-content li {
  margin-bottom: 6px;
}

.about-content hr {
  margin: 20px 0 18px;
  border: none;
  border-top: 1px solid rgba(55, 65, 81, 0.9);
}

[data-theme="light"] .about-content hr {
  border-top-color: rgba(203, 213, 225, 0.9);
}

.about-cta {
  margin-top: 10px;
}

/* --------------------------------------------------------------------------
   11. Collection / News styles
   -------------------------------------------------------------------------- */
.collection-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
}

.collection-item {
  background: var(--feature-card-bg);
  border-radius: var(--radius-lg);
  border: 1px solid rgba(148, 163, 184, 0.4);
  padding: 20px;
  transition: all 0.16s ease-out;
}

.collection-item:hover {
  border-color: var(--accent);
  box-shadow: 0 8px 24px rgba(56, 189, 248, 0.15);
}

[data-theme="light"] .collection-item:hover {
  box-shadow: 0 8px 24px rgba(2, 132, 199, 0.1);
}

.collection-item h3 {
  margin: 0 0 8px;
  font-size: 1rem;
}

.collection-item .meta {
  font-size: 0.8rem;
  color: var(--fg-muted);
  margin-bottom: 8px;
}

.collection-item p {
  font-size: 0.9rem;
  color: var(--fg-muted);
  margin: 0;
}

.empty-state {
  text-align: center;
  padding: 40px 20px;
  color: var(--fg-muted);
}

.empty-state p {
  margin: 0;
  font-size: 0.95rem;
}

/* --------------------------------------------------------------------------
   12. Post styles
   -------------------------------------------------------------------------- */
.post-header {
  margin-bottom: 24px;
}

.post-title {
  font-size: 1.8rem;
  margin: 0 0 8px;
  letter-spacing: 0.01em;
}

.post-byline {
  font-size: 0.85rem;
  color: var(--fg-muted);
}

.post-content {
  background: none;
  border-radius: 0;
  border: none;
  padding: 0;
  box-shadow: none;
  font-size: 0.95rem;
  line-height: 1.75;
}

.post-content h2 {
  font-size: 1.2rem;
  margin: 28px 0 12px;
}

.post-content h2:first-child {
  margin-top: 0;
}

.post-content h3 {
  font-size: 1.05rem;
  margin: 24px 0 10px;
}

.post-content p {
  margin: 0 0 16px;
  color: var(--fg);
}

.post-content p strong {
  font-weight: inherit;
  color: var(--accent);
}

.post-content ul,
.post-content ol {
  margin: 8px 0 16px 24px;
  padding: 0;
  color: var(--fg);
}

.post-content li {
  margin-bottom: 8px;
}

.post-content a {
  color: var(--accent);
}

.post-content hr {
  margin: 28px 0;
  border: none;
  border-top: 1px solid rgba(55, 65, 81, 0.9);
}

[data-theme="light"] .post-content hr {
  border-top-color: rgba(203, 213, 225, 0.9);
}

.post-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 32px;
  padding-top: 20px;
  border-top: 1px solid var(--border-subtle);
}

.post-nav a {
  color: var(--accent);
  font-size: 0.9rem;
}

/* --------------------------------------------------------------------------
   13. Footer
   -------------------------------------------------------------------------- */
footer {
  margin-top: 40px;
  padding-top: 18px;
  border-top: 1px solid rgba(31, 41, 55, 0.9);
  font-size: 0.78rem;
  color: var(--fg-muted);
  display: flex;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

[data-theme="light"] footer {
  border-top-color: rgba(203, 213, 225, 0.9);
}

footer a {
  color: var(--fg-muted);
  text-decoration: none;
}

footer a:hover {
  color: var(--fg);
  text-decoration: underline;
}

/* --------------------------------------------------------------------------
   14. Responsive Breakpoints
   -------------------------------------------------------------------------- */
@media (max-width: 880px) {
  header {
    border-radius: 18px;
  }

  .brand-name {
    font-size: 0.9rem;
  }

  .brand-tagline {
    display: none;
  }

  .hero {
    grid-template-columns: minmax(0, 1fr);
  }

  .hero-left,
  .hero-right {
    border-radius: 20px;
  }

  .section-header {
    flex-direction: column;
    gap: 4px;
  }
}

@media (max-width: 640px) {
  .page-wrap {
    padding-inline: 14px;
  }

  header {
    flex-direction: row;
    align-items: center;
    padding-inline: 12px;
  }

  nav {
    gap: 6px;
  }

  .nav-link {
    padding: 6px 10px;
    font-size: 0.82rem;
  }

  .hero-left,
  .hero-right {
    padding-inline: 18px;
  }

  .hero-title {
    font-size: 1.55rem;
  }

  .feature-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .page-content,
  .about-content,
  .post-content {
    padding-inline: 18px;
  }

  .hero-actions {
    gap: 8px;
  }

  .btn {
    flex: 1 1 auto;
    justify-content: center;
  }

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

/* Hide certain elements on small screens */
@media (max-width: 480px) {
  .brand-text {
    display: none;
  }
}