/* ─── CSS Variables ─────────────────────────────────────────────── */
:root {
  --bg: #f8fafc;
  --bg-card: #ffffff;
  --bg-nav: rgba(248, 250, 252, 0.85);
  --ink: #0f172a;
  --ink-muted: #64748b;
  --accent: #06b6d4;
  --accent-soft: #cffafe;
  --accent-2: #6366f1;
  --accent-2-soft: #e0e7ff;
  --border: #e2e8f0;
  --shadow: 0 2px 20px rgba(15, 23, 42, 0.05);
  --shadow-hover: 0 12px 40px rgba(15, 23, 42, 0.12);
  --radius: 16px;
  --nav-h: 64px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
  --bg: #050816;
  --bg-card: #0f172a;
  --bg-nav: rgba(5, 8, 22, 0.85);
  --ink: #f8fafc;
  --ink-muted: #94a3b8;
  --accent: #22d3ee;
  --accent-soft: #083344;
  --accent-2: #818cf8;
  --accent-2-soft: #312e81;
  --border: #1e293b;
  --shadow: 0 2px 20px rgba(0, 0, 0, 0.25);
  --shadow-hover: 0 12px 40px rgba(0, 0, 0, 0.5);
  --radius: 16px;
  --nav-h: 64px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ─── Reset & Base ──────────────────────────────────────────────── */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: "DM Sans", sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
  transition:
    background var(--transition),
    color var(--transition);
  overflow-x: hidden;
}

::-webkit-scrollbar {
  width: 0.5vw;
  height: 0.5vw;
  background: transparent;
}

::-webkit-scrollbar-thumb {
  border-radius: 1rem;
  background: -webkit-linear-gradient(var(--accent), var(--accent));
}

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

img {
  display: block;
  max-width: 100%;
}

.container {
  width: 100%;
  max-width: 1280px;
  margin: 0 auto;
  padding-inline: 24px;
}

/* ─── Loading Screen ────────────────────────────────────────────── */
#loader {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: var(--bg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 24px;
  transition:
    opacity 0.3s ease,
    visibility 0.3s ease;
}

#loader.hidden {
  opacity: 0;
  visibility: hidden;
}

.loader-logo {
  font-family: "DM Serif Display", serif;
  font-size: 2rem;
  color: var(--accent);
  letter-spacing: -0.02em;
}

.loader-bar {
  width: 160px;
  height: 3px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
}

.loader-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 999px;
  animation: fillBar 1s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

@keyframes fillBar {
  from {
    width: 0;
  }

  to {
    width: 100%;
  }
}

/* ─── Navbar ────────────────────────────────────────────────────── */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--nav-h);
  background: var(--bg-nav);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  padding: 24px 0;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 24px;
  transition:
    background var(--transition),
    border-color var(--transition);
}

.nav-inner {
  display: flex;
  align-items: center;
  width: 100%;
  gap: 16px;
}

.nav-brand {
  font-family: "DM Serif Display", serif;
  font-size: 1.25rem;
  color: var(--accent);
  letter-spacing: -0.02em;
  flex-shrink: 0;
}

.nav-user {
  margin-left: auto;
  display: flex;
  flex-direction: row-reverse;
  gap: 5px;
  font-size: 1rem;
  font-weight: 600;
  color: var(--ink);
}

#navUserName {
  font-size: 1rem;
  font-weight: 600;
  color: var(--ink);
}

#themeToggle {
  width: 40px;
  height: 40px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--ink-muted);
  cursor: pointer;
  transition: all .3s ease;
}

#themeToggle:hover {
  color: var(--accent);
  border-color: var(--accent);
}

/* ─── Hero ──────────────────────────────────────────────────────── */
#hero {
  padding-top: calc(var(--nav-h) + 48px);
  padding-bottom: 56px;
  max-width: 1280px;
  margin: 0 auto;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 5px 13px;
  border-radius: 999px;
  margin-bottom: 20px;
}

.hero-tag svg {
  width: 13px;
  height: 13px;
}

h1 {
  font-family: "DM Serif Display", serif;
  font-size: clamp(2.5rem, 5.5vw, 4rem);
  line-height: 1;
  letter-spacing: -0.03em;
  max-width: 700px;
  margin-bottom: 18px;
}

h1 em {
  font-style: italic;
  color: var(--accent);
}

.hero-desc {
  font-size: 1rem;
  color: var(--ink-muted);
  max-width: 500px;
  margin-bottom: 32px;
  font-weight: 300;
}

.hero-stats {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}

.stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.stat-num {
  font-family: "DM Serif Display", serif;
  font-size: 1.5rem;
  color: var(--ink);
  letter-spacing: -0.02em;
}

.stat-label {
  font-size: 0.75rem;
  color: var(--ink-muted);
  font-weight: 500;
}

/* ─── Search ────────────────────────────────────────────────────── */

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 24px;
  margin-bottom: 24px;
}

.section-title {
  font-family: "DM Serif Display", serif;
  font-size: 1.5rem;
  letter-spacing: -0.02em;
}

.search-wrap {
  position: relative;
  flex: 0 0 auto;
}

.search-wrap svg {
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--ink-muted);
  pointer-events: none;
  width: 16px;
  height: 16px;
}

#search {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--ink);
  font-family: "DM Sans", sans-serif;
  font-size: 0.75rem;
  padding: 9px 14px 9px 40px;
  border-radius: 999px;
  width: 240px;
  outline: none;
  transition:
    border-color var(--transition),
    box-shadow var(--transition);
}

#search:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

#search::placeholder {
  color: var(--ink-muted);
}

/* ─── Course Cards Grid ────────────────────────────────────────── */
#cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 400px), 1fr));
  gap: 24px;
}

/* No-result message */
#no-results {
  display: none;
  grid-column: 1 / -1;
  text-align: center;
  padding: 60px 0;
  color: var(--ink-muted);
  font-size: 1rem;
}

/* ─── Card ──────────────────────────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition:
    box-shadow var(--transition),
    transform var(--transition);
  animation: cardIn 0.5s cubic-bezier(0.4, 0, 0.2, 1) both;
}

.card:hover {
  box-shadow: var(--shadow-hover);
  transform: translateY(-3px);
}

@keyframes cardIn {
  from {
    opacity: 0;
    transform: translateY(18px);
  }

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

/* Stagger card animation */
.card:nth-child(1) {
  animation-delay: 0.05s;
}

.card:nth-child(2) {
  animation-delay: 0.12s;
}

.card:nth-child(3) {
  animation-delay: 0.19s;
}

.card:nth-child(4) {
  animation-delay: 0.26s;
}

.card-header {
  padding: 20px 22px 0;
  display: flex;
  align-items: flex-start;
  gap: 14px;
}

.card-icon {
  width: 44px;
  height: 44px;
  flex-shrink: 0;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
}

.card-meta {
  flex: 1;
  min-width: 0;
}

.card-tag {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 4px;
}

.card-name {
  font-family: "DM Serif Display", serif;
  font-size: 1.25rem;
  letter-spacing: -0.01em;
  line-height: 1.25;
}

.card-desc {
  font-size: 0.75rem;
  color: var(--ink-muted);
  line-height: 1.55;
  padding: 12px 22px 16px;
  font-weight: 300;
}

/* ─── Accordion: Videos & Files ─────────────────────────────────── */
.card-body {
  padding: 0 22px 18px;
  flex: 1;
}

.accordion {
  margin-bottom: 8px;
}

.accordion-btn {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 10px 14px;
  cursor: pointer;
  font-family: "DM Sans", sans-serif;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--ink);
  transition:
    background var(--transition),
    border-color var(--transition);
  text-align: left;
}

.accordion-btn:hover {
  background: var(--border);
}

.accordion-btn:disabled {
  opacity: 0.5;
  cursor: default;
}

.accordion-btn:disabled:hover {
  background: var(--bg);
}

.accordion-btn svg {
  flex-shrink: 0;
}

.accordion-btn .accordion-meta {
  margin-left: auto;
  color: var(--ink-muted);
  font-size: 0.75rem;
  white-space: nowrap;
}

.accordion-btn .chevron {
  transition: transform var(--transition);
  color: var(--ink-muted);
}

.accordion-btn.open .chevron {
  transform: rotate(180deg);
}

.accordion-panel {
  display: none;
  padding: 8px 2px 2px;
  flex-direction: column;
  gap: 6px;
}

.accordion-panel.open {
  display: flex;
}

/* Video link item */
.video-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 12px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  cursor: pointer;
  transition:
    border-color var(--transition),
    background var(--transition);
}

.video-item:hover {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.video-thumb {
  width: 48px;
  height: 32px;
  background: var(--border);
  border-radius: 5px;
  overflow: hidden;
  flex-shrink: 0;
  position: relative;
}

.video-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.video-thumb::after {
  content: "▶";
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.5rem;
  color: #fff;
  background: rgba(0, 0, 0, 0.35);
}

.video-title {
  font-size: 0.75rem;
  font-weight: 500;
  line-height: 1.35;
  flex: 1;
  min-width: 0;
}

.video-duration {
  font-size: 0.75rem;
  color: var(--ink-muted);
  flex-shrink: 0;
}

/* PDF file item */
.file-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 12px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  cursor: pointer;
  transition:
    border-color var(--transition),
    background var(--transition);
}

.file-item:hover {
  border-color: var(--accent-2);
  background: var(--accent-2-soft);
}

.file-icon {
  width: 30px;
  height: 30px;
  background: var(--accent-2-soft);
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  color: var(--accent-2);
}

.file-name {
  font-size: 0.75rem;
  font-weight: 500;
  line-height: 1.35;
  flex: 1;
  min-width: 0;
}

.file-size {
  font-size: 0.75rem;
  color: var(--ink-muted);
  flex-shrink: 0;
}

/* ─── Modals (Video & File & Auth) ─────────────────────────────────────── */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 200;
  background: rgba(10, 8, 6, 0.75);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
  backdrop-filter: blur(4px);
  cursor: pointer;
}

.modal-overlay.open {
  display: flex;
}

.modal-box {
  background: var(--bg-card);
  border-radius: var(--radius);
  overflow: hidden;
  width: 100%;
  max-width: 760px;
  box-shadow: 0 24px 80px rgba(0, 0, 0, 0.4);
  animation: modalIn 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: default;
}

@keyframes modalIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }

  to {
    opacity: 1;
    transform: scale(1);
  }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
}

.modal-title {
  font-size: 1rem;
  font-weight: 600;
  max-width: 80%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.modal-header button {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--ink-muted);
  font-size: 1.25rem;
  line-height: 1;
  transition: color var(--transition);
}

.modal-header button:hover {
  color: var(--ink);
}

.video-modal-wrap {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
}

.video-modal-wrap iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.file-modal-wrap {
  position: relative;
  height: 75vh;
}

.file-modal-wrap iframe {
  width: 100%;
  height: 100%;
  border: none;
}

.auth-modal-box {
  max-width: 400px;
  padding: 40px 36px;
}

.auth-header {
  text-align: center;
  margin-bottom: 28px;
}

.auth-title {
  font-family: "DM Serif Display", serif;
  font-size: 1.75rem;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
  color: var(--accent);
}

.auth-subtitle {
  font-size: 0.75rem;
  color: var(--ink-muted);
  font-weight: 300;
}

#auth-form {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

#auth-student-id,
#auth-password {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--ink);
  font-family: "DM Sans", sans-serif;
  font-size: 1rem;
  padding: 12px 16px;
  border-radius: 10px;
  outline: none;
  width: 100%;
  transition: border-color var(--transition), box-shadow var(--transition);
  text-align: center;
  letter-spacing: 0.05em;
}

#auth-student-id:focus,
#auth-password:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

#auth-student-id.error,
#auth-password.error {
  border-color: #e05252;
  box-shadow: 0 0 0 3px rgba(224, 82, 82, 0.12);
}

#auth-student-id::placeholder,
#auth-password::placeholder {
  color: var(--ink-muted);
  letter-spacing: 0;
}

#auth-error {
  font-size: 0.75rem;
  color: #e05252;
  text-align: center;
  min-height: 1rem;
}

#auth-submit {
  background: var(--ink);
  color: var(--bg-card);
  border: none;
  cursor: pointer;
  font-family: "DM Sans", sans-serif;
  font-size: 1rem;
  font-weight: 600;
  padding: 12px;
  border-radius: 10px;
  width: 100%;
  transition: background var(--transition), box-shadow var(--transition);
  margin-top: 4px;
}

#auth-submit:hover {
  background: var(--accent);
  box-shadow: 0 4px 16px var(--accent-soft);
}

#auth-submit:disabled {
  opacity: 0.5;
  box-shadow: unset;
  cursor: not-allowed;
  background: var(--ink);
}

/* ─── Footer ────────────────────────────────────────────────────── */
footer {
  margin-top: 24px;
  border-top: 1px solid var(--border);
  text-align: center;
  padding: 24px 24px;
  font-size: 0.75rem;
  color: var(--ink-muted);
  font-weight: 300;
}

footer span {
  color: var(--accent);
}