/* DualRead theme — navy + cream paper aesthetic */

:root {
  --bg: #f8f3e8;
  --bg-card: #ffffff;
  --ink: #1a2942;
  --ink-soft: #5b6a7f;
  --ink-muted: #8b95a5;
  --accent: #6f1d2a;
  --accent-soft: #fce8eb;
  --border: #e3dcc9;
  --success: #1d6b3a;
  --error: #b3261e;
  --shadow: 0 1px 2px rgba(26, 41, 66, 0.06), 0 4px 12px rgba(26, 41, 66, 0.04);
  --font-serif: 'Iowan Old Style', 'Palatino Linotype', 'Charter', Georgia, serif;
  --font-ui: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  --radius-sm: 6px;
  --radius: 8px;
  --radius-lg: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-serif);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3, h4 {
  font-family: var(--font-serif);
  color: var(--ink);
  letter-spacing: -0.01em;
  line-height: 1.25;
  margin: 0 0 0.6rem;
}

[hidden] { display: none !important; }

/* Layout */
.container {
  max-width: 920px;
  margin: 0 auto;
  padding: 0 1rem;
}

.main { min-height: calc(100vh - 140px); padding: 1.5rem 0 3rem; }

.footer {
  border-top: 1px solid var(--border);
  padding: 1.2rem 0;
  font-size: 0.85rem;
  color: var(--ink-muted);
  text-align: center;
  font-family: var(--font-ui);
}

/* Nav */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  font-family: var(--font-ui);
}
.nav-inner {
  max-width: 920px;
  margin: 0 auto;
  padding: 0.75rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.nav-brand {
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--accent);
  letter-spacing: -0.01em;
}
.nav-links { display: flex; align-items: center; gap: 0.4rem; flex-wrap: wrap; }
.nav-link {
  padding: 0.45rem 0.8rem;
  border-radius: var(--radius-sm);
  color: var(--ink-soft);
  font-size: 0.92rem;
}
.nav-link:hover { background: var(--bg); color: var(--ink); text-decoration: none; }
.nav-link-primary {
  background: var(--accent);
  color: var(--bg);
}
.nav-link-primary:hover { background: #581522; color: var(--bg); text-decoration: none; }
.nav-user { font-size: 0.9rem; color: var(--ink-soft); }
.btn-link {
  background: none;
  border: none;
  padding: 0.45rem 0.8rem;
  color: var(--ink-soft);
  cursor: pointer;
  font: inherit;
  font-size: 0.92rem;
  border-radius: var(--radius-sm);
}
.btn-link:hover { background: var(--bg); color: var(--accent); }

/* Buttons */
.btn {
  display: inline-block;
  font-family: var(--font-ui);
  font-weight: 500;
  font-size: 0.95rem;
  padding: 0.6rem 1.4rem;
  border-radius: var(--radius);
  border: 1px solid transparent;
  cursor: pointer;
  text-align: center;
  transition: background 0.15s, transform 0.05s, border-color 0.15s;
}
.btn:active { transform: translateY(1px); }
.btn-primary {
  background: var(--accent);
  color: var(--bg);
}
.btn-primary:hover { background: #581522; text-decoration: none; }
.btn-primary:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.btn-secondary {
  background: transparent;
  color: var(--ink);
  border-color: var(--border);
}
.btn-secondary:hover { border-color: var(--ink-soft); background: var(--bg-card); text-decoration: none; }

/* Forms */
.auth-form, .upload-form {
  max-width: 480px;
  margin: 2rem auto;
  background: var(--bg-card);
  padding: 2rem;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  font-family: var(--font-ui);
}
.upload-form { max-width: 720px; }
.form-row { margin-bottom: 1rem; }
.form-label {
  display: block;
  font-weight: 500;
  margin-bottom: 0.4rem;
  color: var(--ink);
  font-size: 0.92rem;
}
.form-input, .form-textarea {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.6rem 0.75rem;
  font: inherit;
  background: var(--bg-card);
  color: var(--ink);
  transition: border-color 0.15s, box-shadow 0.15s;
}
.form-input:focus, .form-textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.form-textarea {
  font-family: 'SF Mono', 'Menlo', 'Consolas', monospace;
  font-size: 0.85rem;
  line-height: 1.5;
  min-height: 240px;
  resize: vertical;
}
.form-help {
  display: block;
  margin-top: 0.35rem;
  font-size: 0.82rem;
  color: var(--ink-muted);
}
.form-error {
  color: var(--error);
  font-size: 0.88rem;
  margin-top: 0.5rem;
  border-radius: var(--radius-sm);
}
.form-error:not(:empty) {
  background: var(--accent-soft);
  padding: 0.5rem 0.75rem;
}
.form-progress { color: var(--success); font-size: 0.85rem; margin-top: 0.5rem; }
.auth-alt-link {
  text-align: center;
  font-size: 0.88rem;
  margin-top: 1.2rem;
  color: var(--ink-soft);
}
.auth-alt-link a { color: var(--accent); font-weight: 500; }

/* Hero / Landing */
.hero { text-align: center; padding: 3rem 0 2rem; }
.hero-title { font-size: 2.5rem; line-height: 1.15; margin-bottom: 1rem; }
.hero-sub {
  font-size: 1.15rem;
  color: var(--ink-soft);
  max-width: 640px;
  margin: 0 auto 1.8rem;
}
.cta-row { display: flex; gap: 0.8rem; justify-content: center; flex-wrap: wrap; }
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  margin: 3rem 0;
}
.feature-card {
  background: var(--bg-card);
  padding: 1.5rem;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
}
.feature-title {
  font-weight: 600;
  margin-bottom: 0.5rem;
  font-size: 1.1rem;
  color: var(--ink);
}

/* Library */
.library-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  gap: 1rem;
  flex-wrap: wrap;
}
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.2rem;
}
.lesson-card {
  background: var(--bg-card);
  padding: 1.2rem;
  border-radius: 10px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  position: relative;
}
.lesson-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 2px 4px rgba(26, 41, 66, 0.08), 0 8px 20px rgba(26, 41, 66, 0.06);
}
.lesson-title {
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--accent);
  margin-bottom: 0.4rem;
  display: block;
}
.lesson-meta {
  font-size: 0.82rem;
  color: var(--ink-muted);
  font-family: var(--font-ui);
}
.btn-icon-edit, .btn-icon-delete {
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.3rem 0.55rem;
  font-size: 0.8rem;
  cursor: pointer;
  color: var(--ink-soft);
  font-family: var(--font-ui);
  transition: border-color 0.15s, color 0.15s;
}
.btn-icon-edit:hover { color: var(--ink); border-color: var(--ink-soft); }
.btn-icon-delete:hover { color: var(--error); border-color: var(--error); }
.empty-state {
  text-align: center;
  padding: 3rem 1.5rem;
  border: 1px dashed var(--border);
  border-radius: var(--radius-lg);
  color: var(--ink-muted);
}

/* Reader (paper aesthetic) */
.reader-screen {
  background: var(--bg);
  padding: 2rem 0 6rem;
  min-height: 100vh;
}
.reader-content {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 1.25rem;
  font-family: var(--font-serif);
  font-size: 1.25rem;
  line-height: 1.9;
}
.reader-item {
  margin-bottom: 2.4rem;
  opacity: 0.35;
  transition: opacity 0.4s ease, transform 0.4s ease;
  transform: scale(1);
  transform-origin: left center;
  will-change: opacity, transform;
}
.reader-item-active {
  opacity: 1;
  transform: scale(1.02);
}
.reader-en {
  font-weight: 500;
  color: var(--ink);
  font-size: 1.3rem;
  margin-bottom: 0.6rem;
  line-height: 1.55;
}
.reader-vi {
  font-style: italic;
  color: var(--ink-muted);
  font-size: 1.05rem;
  line-height: 1.6;
}
.reader-controls {
  position: sticky;
  bottom: 0;
  background: var(--bg-card);
  box-shadow: 0 -2px 12px rgba(26, 41, 66, 0.08);
  padding: 0.8rem 1rem;
  display: flex;
  gap: 0.6rem;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  font-family: var(--font-ui);
  border-top: 1px solid var(--border);
}
.ctrl-btn {
  padding: 0.5rem 1rem;
  font-weight: 500;
  border-radius: var(--radius);
  color: var(--ink);
  background: var(--bg-card);
  border: 1px solid var(--border);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.92rem;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.ctrl-btn:hover { border-color: var(--ink-soft); }
.ctrl-btn-active {
  background: var(--ink);
  color: var(--bg);
  border-color: var(--ink);
}
.ctrl-select {
  padding: 0.4rem 0.6rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--ink);
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
}
.ctrl-progress {
  font-variant-numeric: tabular-nums;
  color: var(--ink-muted);
  font-size: 0.88rem;
  padding: 0 0.5rem;
}

/* Error pages */
.error-page { text-align: center; padding: 4rem 1rem; }
.error-title { font-size: 2rem; margin-bottom: 0.8rem; }
.error-message {
  color: var(--ink-muted);
  margin-bottom: 2rem;
  font-size: 1.05rem;
}

/* Utility */
.text-muted { color: var(--ink-muted); }
.code-block {
  background: #1a2942;
  color: #f8f3e8;
  padding: 1rem;
  border-radius: var(--radius);
  overflow-x: auto;
  font-family: 'SF Mono', 'Menlo', 'Consolas', monospace;
  font-size: 0.85rem;
  line-height: 1.55;
}
.upload-help { margin: 1rem 0; font-family: var(--font-ui); font-size: 0.9rem; }
.upload-help summary {
  cursor: pointer;
  font-weight: 500;
  color: var(--ink-soft);
  padding: 0.4rem 0;
}
.upload-help summary:hover { color: var(--accent); }
.upload-help[open] summary { color: var(--ink); margin-bottom: 0.6rem; }

/* Responsive */
@media (max-width: 720px) {
  html, body { font-size: 15.5px; }
  .hero { padding: 2rem 0 1.5rem; }
  .hero-title { font-size: 2rem; }
  .hero-sub { font-size: 1rem; }
  .feature-grid { grid-template-columns: 1fr; gap: 1rem; margin: 2rem 0; }
  .nav-inner { padding: 0.6rem 1rem; flex-wrap: wrap; gap: 0.5rem; }
  .nav-links { gap: 0.2rem; }
  .nav-link { padding: 0.4rem 0.6rem; font-size: 0.88rem; }
  .auth-form, .upload-form { margin: 1rem auto; padding: 1.25rem; border-radius: var(--radius); }
  .reader-content { font-size: 1.12rem; padding: 0 1rem; }
  .reader-en { font-size: 1.17rem; }
  .reader-vi { font-size: 0.95rem; }
  .reader-controls { padding: 0.6rem 0.8rem; gap: 0.4rem; }
  .ctrl-btn { padding: 0.45rem 0.8rem; font-size: 0.88rem; }
  .error-title { font-size: 1.6rem; }
}