/* ============================================================
   Subject Detail Page Styles
   Apple-inspired dark theme · Glass morphism · Inter font
   ============================================================ */

/* ---- Page Base ---- */
.subject-page {
  min-height: 100vh;
  background: var(--color-bg-primary);
  color: var(--color-text-primary);
  font-family: var(--font-family-primary);
}

/* ============================================================
   Navbar & language switcher
   ------------------------------------------------------------
   The top bar is shared across every page and is defined ONCE in
   home.css (which this page also loads). Page-specific navbar
   overrides used to live here, but they gave the subject page a
   navbar that differed in size/spacing from the other pages, so
   they were removed for a single, consistent top bar.
   ============================================================ */

/* ============================================================
   Subject Hero / Header Section
   ============================================================ */
.subject-hero {
  position: relative;
  padding: calc(var(--navbar-height) + var(--spacing-4xl)) var(--spacing-lg) var(--spacing-3xl);
  overflow: hidden;
  text-align: center;
}

.subject-hero__bg {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 0;
}

.subject-hero__orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.12;
}

.subject-hero__orb--1 {
  width: 500px;
  height: 500px;
  background: var(--color-accent-primary);
  top: -100px;
  left: 50%;
  transform: translateX(-60%);
}

.subject-hero__orb--2 {
  width: 400px;
  height: 400px;
  background: var(--color-accent-secondary);
  top: 50px;
  left: 50%;
  transform: translateX(10%);
}

.subject-hero__content {
  position: relative;
  z-index: 1;
  max-width: 700px;
  margin: 0 auto;
}

.subject-hero__icon {
  font-size: 4rem;
  line-height: 1;
  margin-bottom: var(--spacing-lg);
  display: block;
  filter: drop-shadow(0 4px 12px rgba(0, 0, 0, 0.15));
}

.subject-hero__id {
  display: inline-block;
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-accent-primary);
  background: rgba(0, 113, 227, 0.12);
  border: 1px solid rgba(0, 113, 227, 0.25);
  border-radius: var(--radius-full);
  padding: var(--spacing-xs) var(--spacing-md);
  margin-bottom: var(--spacing-md);
}

.subject-hero__title {
  font-size: clamp(var(--font-size-3xl), 5vw, var(--font-size-5xl));
  font-weight: var(--font-weight-bold);
  letter-spacing: var(--letter-spacing-tight);
  line-height: var(--line-height-tight);
  color: var(--color-text-primary);
  margin: 0 0 var(--spacing-lg);
}

.subject-hero__description {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
  margin: 0 auto;
  max-width: 560px;
}

/* ---- Star Button ---- */
.subject-star-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-lg);
  margin-top: var(--spacing-md);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  font-family: inherit;
  color: var(--color-text-secondary);
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.subject-star-btn:hover {
  color: var(--color-text-primary);
  background: rgba(255, 255, 255, 0.2);
  border-color: rgba(255, 255, 255, 0.3);
}

.subject-star-btn .star-icon {
  transition: transform var(--transition-fast), fill var(--transition-fast);
}

.subject-star-btn:hover .star-icon {
  transform: scale(1.1);
}

/* Starred state */
.subject-star-btn.is-starred {
  color: #fbbf24;
  background: rgba(251, 191, 36, 0.15);
  border-color: rgba(251, 191, 36, 0.3);
}

.subject-star-btn.is-starred .star-icon {
  fill: #fbbf24;
}

.subject-star-btn.is-starred:hover {
  background: rgba(229, 62, 62, 0.15);
  border-color: rgba(229, 62, 62, 0.3);
  color: #e53e3e;
}

.subject-star-btn.is-starred:hover .star-icon {
  fill: #e53e3e;
}

/* ============================================================
   Breadcrumb
   ============================================================ */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
  padding: var(--spacing-md) var(--spacing-lg);
  max-width: var(--container-wide);
  margin: 0 auto;
}

.breadcrumb__link {
  color: var(--color-text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.breadcrumb__link:hover {
  color: var(--color-accent-primary);
}

.breadcrumb__sep {
  color: var(--color-text-tertiary);
  user-select: none;
}

.breadcrumb__current {
  color: var(--color-text-primary);
  font-weight: var(--font-weight-medium);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 240px;
}

/* ============================================================
   Resources Section
   ============================================================ */
.resources {
  max-width: var(--container-wide);
  margin: 0 auto;
  padding: var(--spacing-xl) var(--spacing-lg) var(--spacing-5xl);
}

.resources__header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: var(--spacing-2xl);
}

.resources__title {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.resources__count {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
}

/* ============================================================
   Cohort Sections
   ============================================================ */
.cohort-section {
  margin-bottom: var(--spacing-3xl);
}

.cohort-section:last-child {
  margin-bottom: 0;
}

.cohort-section__header {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
  padding-bottom: var(--spacing-md);
  border-bottom: 1px solid var(--color-border);
}

.cohort-section__label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-text-tertiary);
  flex: 1;
}

.cohort-section__title {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.cohort-section__pill {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-full);
  padding: 2px var(--spacing-sm);
}

.cohort-section__grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--spacing-lg);
}

/* ── Type sections (grouped by material type: exam / answer / assignment) ── */
.type-section__icon {
  font-size: 1.35rem;
  line-height: 1;
  flex-shrink: 0;
}

/* Title takes the remaining width so the count pill is pushed to the right,
   mirroring the cohort-section__label flex behaviour. */
.type-section__title {
  flex: 1;
}

/* ============================================================
   Resource Cards
   ============================================================ */
.resource-card {
  position: relative;
  display: flex;
  flex-direction: column;
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  gap: var(--spacing-md);
  text-decoration: none;
  overflow: hidden;
  cursor: pointer;
  /* ── Scroll-reveal initial state ── */
  opacity: 0;
  transform: translateY(20px);
  will-change: transform, opacity;
  /* Entrance transition: opacity slow (fade-in feel), transform slow for reveal */
  transition:
    opacity 0.5s ease,
    transform 0.5s ease,
    border-color var(--transition-base),
    box-shadow var(--transition-base),
    background var(--transition-base);
}

.resource-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg,
    rgba(255, 255, 255, 0.5) 0%,
    transparent 60%);
  border-radius: inherit;
  pointer-events: none;
}

.resource-card:hover {
  transform: translateY(-4px);
  border-color: var(--glass-border-hover);
  box-shadow: var(--shadow-lg), 0 0 0 1px rgba(0, 113, 227, 0.15);
  background: var(--color-surface-glass-hover);
}

/* Card top row: icon + badges */
.resource-card__top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--spacing-sm);
}

.resource-card__icon {
  width: 44px;
  height: 44px;
  flex-shrink: 0;
  border-radius: var(--radius-md);
  background: rgba(229, 57, 53, 0.12);
  border: 1px solid rgba(229, 57, 53, 0.2);
  display: flex;
  align-items: center;
  justify-content: center;
}

.resource-card__icon svg {
  width: 22px;
  height: 22px;
  color: #e57373;
}

/* Badge row */
.resource-card__badges {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  justify-content: flex-end;
}

/* Card body */
.resource-card__body {
  flex: 1;
}

.resource-card__filename {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  line-height: var(--line-height-normal);
  word-break: break-word;
  margin: 0 0 var(--spacing-xs);
}

.resource-card__meta {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.resource-card__meta-dot {
  width: 3px;
  height: 3px;
  border-radius: 50%;
  background: var(--color-text-tertiary);
  flex-shrink: 0;
}

/* Card action */
.resource-card__action {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-sm);
  padding-top: var(--spacing-sm);
  border-top: 1px solid var(--color-border);
  margin-top: auto;
}

.resource-card__action-label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  color: var(--color-accent-primary);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 4px;
  transition: gap var(--transition-fast);
}

.resource-card:hover .resource-card__action-label {
  gap: 7px;
}

.resource-card__action-label svg {
  width: 14px;
  height: 14px;
}

.resource-card__action-size {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
}

/* ============================================================
   Badges
   ============================================================ */
.badge {
  display: inline-flex;
  align-items: center;
  font-size: 0.65rem;
  font-weight: var(--font-weight-semibold);
  letter-spacing: 0.07em;
  text-transform: uppercase;
  border-radius: var(--radius-full);
  padding: 2px 8px;
  line-height: 1.6;
  white-space: nowrap;
}

.badge--version {
  background: rgba(88, 86, 214, 0.18);
  color: #9d9bf7;
  border: 1px solid rgba(88, 86, 214, 0.25);
}

.badge--type {
  background: rgba(0, 113, 227, 0.15);
  color: #5ac8fa;
  border: 1px solid rgba(0, 113, 227, 0.22);
}

/* Answer sheet badge - special styling */
.badge--answer {
  background: rgba(52, 199, 89, 0.18);
  color: #34c759;
  border: 1px solid rgba(52, 199, 89, 0.3);
}

/* Answer card special styling */
.resource-card--answer {
  border-color: rgba(52, 199, 89, 0.3);
}

.resource-card--answer:hover {
  border-color: rgba(52, 199, 89, 0.6);
  box-shadow: 0 4px 20px rgba(52, 199, 89, 0.15);
}

.resource-card__icon--answer {
  color: #34c759;
}

.badge--cohort {
  background: rgba(52, 199, 89, 0.12);
  color: #5ad87a;
  border: 1px solid rgba(52, 199, 89, 0.2);
}

/* ============================================================
   Empty State
   ============================================================ */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--spacing-5xl) var(--spacing-lg);
}

.empty-state__icon {
  font-size: 3.5rem;
  margin-bottom: var(--spacing-lg);
  opacity: 0.5;
}

.empty-state__title {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin: 0 0 var(--spacing-sm);
}

.empty-state__message {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  line-height: var(--line-height-relaxed);
  max-width: 400px;
  margin: 0 0 var(--spacing-xl);
}

.empty-state__link {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-accent-primary);
  text-decoration: none;
  padding: var(--spacing-sm) var(--spacing-lg);
  border: 1px solid rgba(0, 113, 227, 0.3);
  border-radius: var(--radius-full);
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.empty-state__link:hover {
  background: rgba(0, 113, 227, 0.1);
  border-color: rgba(0, 113, 227, 0.5);
}

/* ============================================================
   Error State (invalid subject ID)
   ============================================================ */
.error-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 80vh;
  text-align: center;
  padding: var(--spacing-lg);
}

.error-state__code {
  font-size: 6rem;
  font-weight: var(--font-weight-bold);
  background: var(--color-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  margin-bottom: var(--spacing-md);
}

.error-state__title {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  margin: 0 0 var(--spacing-sm);
}

.error-state__message {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  max-width: 400px;
  line-height: var(--line-height-relaxed);
  margin: 0 0 var(--spacing-xl);
}

.error-state__link {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-xl);
  background: var(--color-gradient);
  color: #fff;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-full);
  text-decoration: none;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
}

.error-state__link:hover {
  opacity: 0.88;
  transform: translateY(-1px);
}

/* ============================================================
   Subject Page Footer
   ============================================================ */
.subject-footer {
  border-top: 1px solid var(--color-border);
  padding: var(--spacing-2xl) var(--spacing-lg);
  text-align: center;
}

.subject-footer__text {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
}

.subject-footer__text a {
  color: var(--color-text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.subject-footer__text a:hover {
  color: var(--color-accent-primary);
}

.subject-footer__disclaimer {
  max-width: 640px;
  margin: var(--spacing-sm) auto 0;
  font-size: var(--font-size-xs);
  line-height: 1.5;
  color: var(--color-text-tertiary);
  opacity: 0.85;
}

/* ============================================================
   Scroll-triggered Animations
   ============================================================ */

/* JS adds .is-visible via IntersectionObserver → triggers entrance transition.
   Initial state (opacity:0, translateY(20px)) lives in the .resource-card block above. */
.resource-card.is-visible {
  opacity: 1;
  transform: translateY(0);
  /* After entrance, switch transform to snappy timing so hover feels instant */
  transition:
    opacity 0.5s ease,
    transform var(--transition-base),
    border-color var(--transition-base),
    box-shadow var(--transition-base),
    background var(--transition-base);
}

/* Hover: snappy -4px lift using the fast var(--transition-base) above */
.resource-card.is-visible:hover {
  transform: translateY(-4px);
}

/* Stagger delays for grid children */
.resource-card:nth-child(1) { transition-delay: 0.04s; }
.resource-card:nth-child(2) { transition-delay: 0.10s; }
.resource-card:nth-child(3) { transition-delay: 0.16s; }
.resource-card:nth-child(4) { transition-delay: 0.22s; }
.resource-card:nth-child(5) { transition-delay: 0.28s; }
.resource-card:nth-child(6) { transition-delay: 0.34s; }

/* Cohort sections slide in */
.cohort-section {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

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

/* Hero elements animate on load */
.subject-hero__content .animate-on-load {
  opacity: 0;
  transform: translateY(20px);
  animation: fadeSlideUp 0.6s ease forwards;
}

.subject-hero__content .animate-on-load--delay-1 { animation-delay: 0.1s; }
.subject-hero__content .animate-on-load--delay-2 { animation-delay: 0.2s; }
.subject-hero__content .animate-on-load--delay-3 { animation-delay: 0.3s; }
.subject-hero__content .animate-on-load--delay-4 { animation-delay: 0.4s; }

@keyframes fadeSlideUp {
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ============================================================
   Responsive Design  (tiers: ≤480 · ≤768 · ≤1024 · ≥1025 · ≥1440)
   Navbar collapse is handled with home.css + the ≤767 rule near
   the top of this file; below covers the subject content.
   ============================================================ */

/* ---- Tablet (≤1024px) ---- */
@media (max-width: 1024px) {
  .subject-hero { padding-left: var(--spacing-lg); padding-right: var(--spacing-lg); }
  .resources { padding-left: var(--spacing-lg); padding-right: var(--spacing-lg); }
  .cohort-section__grid { grid-template-columns: repeat(2, 1fr); }
}

/* ---- Phones (≤768px) ---- */
@media (max-width: 768px) {
  .subject-hero {
    padding-top: calc(var(--navbar-height) + var(--spacing-2xl));
    padding-bottom: var(--spacing-2xl);
    padding-left: var(--spacing-md);
    padding-right: var(--spacing-md);
  }
  .subject-hero__icon { font-size: 3rem; }
  .subject-hero__title { font-size: var(--font-size-3xl); }
  .subject-hero__description { font-size: var(--font-size-base); }

  .breadcrumb { padding-left: var(--spacing-md); padding-right: var(--spacing-md); }
  .breadcrumb__current { max-width: 160px; }

  .resources { padding-left: var(--spacing-md); padding-right: var(--spacing-md); }
  .resources__header {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-xl);
  }
  .resources__title { font-size: var(--font-size-xl); }

  .cohort-section__grid { grid-template-columns: 1fr; gap: var(--spacing-md); }
  .resource-card { padding: var(--spacing-md); }
}

/* ---- Small phones (≤480px) ---- */
@media (max-width: 480px) {
  .subject-hero {
    padding-top: calc(var(--navbar-height) + var(--spacing-xl));
    padding-bottom: var(--spacing-xl);
    padding-left: var(--spacing-sm);
    padding-right: var(--spacing-sm);
  }
  .subject-hero__icon { font-size: 2.5rem; }
  .subject-hero__title { font-size: var(--font-size-2xl); }
  .subject-hero__description { font-size: var(--font-size-sm); }

  .breadcrumb { padding-left: var(--spacing-sm); padding-right: var(--spacing-sm); gap: var(--spacing-xs); }
  .breadcrumb__link,
  .breadcrumb__current { font-size: var(--font-size-xs); }
  .breadcrumb__current { max-width: 120px; }

  .resources { padding-left: var(--spacing-sm); padding-right: var(--spacing-sm); }
  .resources__title { font-size: var(--font-size-lg); }
  .cohort-section { margin-bottom: var(--spacing-2xl); }
  .cohort-section__title { font-size: var(--font-size-base); }

  .resource-card { padding: var(--spacing-md); }
  .resource-card__filename { font-size: var(--font-size-sm); }
  .resource-card__meta { flex-wrap: wrap; }
  .resource-card__action {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-xs);
  }
  .badge { font-size: 0.6rem; padding: 1px 6px; }

  .empty-state { padding: var(--spacing-3xl) var(--spacing-sm); }
  .empty-state__icon { font-size: 2.5rem; }
  .empty-state__title { font-size: var(--font-size-lg); }
  .empty-state__message { font-size: var(--font-size-sm); }

  .error-state { padding: var(--spacing-3xl) var(--spacing-sm); }
  .error-state__code { font-size: 3.5rem; }
  .error-state__title { font-size: var(--font-size-xl); }
  .error-state__message { font-size: var(--font-size-sm); }

  .subject-footer { padding: var(--spacing-xl) var(--spacing-sm); }
  .subject-footer__text { font-size: var(--font-size-xs); }
}

/* ---- Resource grid on larger screens ---- */
@media (min-width: 1025px) { .cohort-section__grid { grid-template-columns: repeat(3, 1fr); } }
@media (min-width: 1440px) {
  .subject-hero__content { max-width: 900px; }
  .cohort-section__grid { grid-template-columns: repeat(4, 1fr); }
}

/* ---- Landscape phones: shrink the tall hero ---- */
@media (max-width: 1023px) and (orientation: landscape) {
  .subject-hero {
    padding-top: calc(var(--navbar-height) + var(--spacing-lg));
    padding-bottom: var(--spacing-lg);
  }
  .subject-hero__icon { font-size: 2.5rem; }
  .subject-hero__title { font-size: var(--font-size-2xl); }
}

/* ---- Reduced motion ---- */
@media (prefers-reduced-motion: reduce) {
  .resource-card,
  .cohort-section,
  .subject-hero__content .animate-on-load { animation: none; transition: none; }
  .resource-card.is-visible,
  .cohort-section.is-visible { opacity: 1; transform: none; }
}