:root {
  --bg: #f3f6fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #1d4ed8;
  --primary-dark: #1e3a8a;
  --green: #16a34a;
  --border: #e5e7eb;
  --danger: #b91c1c;
  --shadow: 0 18px 45px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.landing-body {
  min-height: 100vh;
  display: grid;
  place-items: center;
  background:
    radial-gradient(circle at top left, rgba(29, 78, 216, 0.16), transparent 34%),
    linear-gradient(135deg, #eff6ff 0%, #f8fafc 100%);
  padding: 24px;
}

.landing-card,
.auth-card,
.panel,
.course-card,
.file-list {
  background: var(--card);
  border: 1px solid rgba(229, 231, 235, 0.9);
  box-shadow: var(--shadow);
}

.landing-card {
  width: min(760px, 100%);
  padding: 46px;
  border-radius: 28px;
  text-align: center;
}

.badge,
.eyebrow {
  display: inline-block;
  color: var(--primary);
  background: #dbeafe;
  padding: 7px 12px;
  border-radius: 999px;
  font-size: 13px;
  font-weight: 700;
}

h1, h2, h3, p {
  margin-top: 0;
}

.landing-card h1 {
  font-size: clamp(32px, 5vw, 52px);
  margin: 22px 0 8px;
  color: var(--primary-dark);
}

.landing-card h2 {
  font-size: clamp(18px, 3vw, 26px);
  color: #374151;
}

.landing-card p,
.muted,
.panel p,
.course-card p,
.file-item p {
  color: var(--muted);
  line-height: 1.6;
}

.primary-btn,
.secondary-btn,
.download-btn {
  border: 0;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  justify-content: center;
  align-items: center;
  border-radius: 12px;
  font-weight: 700;
  transition: 0.18s ease;
}

.primary-btn {
  background: var(--primary);
  color: white;
  padding: 13px 24px;
}

.primary-btn:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}

.primary-btn.full {
  width: 100%;
  margin-top: 18px;
}

.primary-btn.compact,
.secondary-btn {
  padding: 11px 16px;
}

.secondary-btn {
  background: white;
  color: var(--primary-dark);
  border: 1px solid var(--border);
}

.secondary-btn:hover {
  background: #eff6ff;
}

.auth-wrapper {
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px;
}

.auth-card {
  width: min(440px, 100%);
  border-radius: 24px;
  padding: 32px;
}

.auth-card h1 {
  margin-top: 12px;
}

label {
  display: block;
  margin: 16px 0 7px;
  font-weight: 700;
}

input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 13px 14px;
  font-size: 15px;
  outline: none;
}

input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(29, 78, 216, 0.12);
}

.message {
  color: var(--danger);
  min-height: 22px;
  margin-top: 14px;
  text-align: center;
}

.notice {
  background: #eff6ff;
  color: #1e40af;
  border: 1px solid #bfdbfe;
  padding: 13px;
  border-radius: 12px;
}

.topbar {
  max-width: 1160px;
  margin: 0 auto;
  padding: 28px 22px 12px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}

.topbar h1 {
  margin: 8px 0 0;
}

.container {
  max-width: 1160px;
  margin: 0 auto;
  padding: 12px 22px 40px;
}

.panel {
  border-radius: 22px;
  padding: 22px;
  margin-bottom: 22px;
}

.intro-panel {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 22px;
}

.search-input {
  max-width: 320px;
  background: #f9fafb;
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 18px;
}

.course-card {
  border-radius: 22px;
  padding: 22px;
  cursor: pointer;
  display: flex;
  gap: 15px;
  align-items: flex-start;
  transition: 0.18s ease;
}

.course-card:hover {
  transform: translateY(-4px);
  border-color: #bfdbfe;
}

.folder-icon,
.file-icon {
  font-size: 34px;
  line-height: 1;
}

.file-list {
  border-radius: 22px;
  overflow: hidden;
}

.file-item {
  padding: 16px 18px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}

.file-item:last-child {
  border-bottom: 0;
}

.file-main {
  display: flex;
  align-items: center;
  gap: 14px;
  min-width: 0;
}

.file-main h3 {
  margin-bottom: 5px;
  word-break: break-word;
}

.download-btn {
  background: var(--green);
  color: white;
  padding: 10px 14px;
  white-space: nowrap;
}

.download-btn:hover {
  filter: brightness(0.95);
}

.back-link {
  color: var(--primary-dark);
  text-decoration: none;
  font-weight: 700;
}

.empty {
  text-align: center;
  color: var(--muted);
  padding: 28px;
}

.hidden {
  display: none;
}

@media (max-width: 720px) {
  .landing-card,
  .auth-card {
    padding: 26px;
  }

  .topbar,
  .intro-panel,
  .file-item {
    flex-direction: column;
    align-items: stretch;
  }

  .search-input {
    max-width: 100%;
  }

  .primary-btn.compact,
  .secondary-btn {
    width: 100%;
  }
}