:root,
[data-theme="dark"] {
  color-scheme: dark;
  --font: "Inter", system-ui, sans-serif;
  --font-display: "Oswald", sans-serif;
  --radius: 0.75rem;
  --radius-lg: 1rem;
  --bg: #050505;
  --panel: #0a0a0a;
  --panel2: #121212;
  --text: #ffffff;
  --text-soft: #d4d4d4;
  --muted: #a3a3a3;
  --dim: #737373;
  --accent: #60a5fa;
  --accent2: #4ade80;
  --danger: #f87171;
  --border: rgba(255, 255, 255, 0.1);
  --border-strong: rgba(255, 255, 255, 0.15);
  --bg-gradient-1: rgba(59, 130, 246, 0.1);
  --bg-gradient-2: rgba(99, 102, 241, 0.08);
  --surface-input: rgba(255, 255, 255, 0.05);
  --surface-muted: rgba(255, 255, 255, 0.04);
  --surface-btn: rgba(255, 255, 255, 0.05);
  --surface-panel-shine: rgba(255, 255, 255, 0.03);
  --surface-toc: rgba(255, 255, 255, 0.04);
  --surface-task: rgba(255, 255, 255, 0.03);
  --surface-badge: rgba(255, 255, 255, 0.05);
  --placeholder: #525252;
  --term-bg: rgba(59, 130, 246, 0.12);
  --term-border: rgba(59, 130, 246, 0.35);
  --term-known-bg: rgba(74, 222, 128, 0.12);
  --term-known-border: rgba(74, 222, 128, 0.45);
  --btn-accent-bg: linear-gradient(to right, #6366f1, #2563eb, #06b6d4);
  --btn-accent-border: transparent;
  --btn-accent-shadow: 0 4px 15px rgba(79, 70, 229, 0.35);
  --btn-accent-shadow-hover: 0 0 40px 8px rgba(37, 99, 235, 0.35);
  --btn-hover-border: rgba(255, 255, 255, 0.3);
  --toc-active-bg: rgba(59, 130, 246, 0.1);
  --toc-active-border: rgba(59, 130, 246, 0.35);
  --toc-hover-border: rgba(59, 130, 246, 0.25);
  --focus-border: rgba(59, 130, 246, 0.5);
  --focus-ring: rgba(59, 130, 246, 0.2);
  --modal-bg: #0a0a0a;
  --overlay-bg: rgba(0, 0, 0, 0.6);
  --shadow-modal: 0 20px 60px rgba(0, 0, 0, 0.5);
  --good-bg: rgba(74, 222, 128, 0.12);
  --good-border: rgba(74, 222, 128, 0.45);
  --bad-bg: rgba(248, 113, 113, 0.12);
  --bad-border: rgba(248, 113, 113, 0.45);
}

[data-theme="light"] {
  color-scheme: light;
  --bg: #f5f7fb;
  --panel: #ffffff;
  --panel2: #ffffff;
  --text: #171717;
  --text-soft: #404040;
  --muted: #737373;
  --dim: #a3a3a3;
  --accent: #2563eb;
  --accent2: #16a34a;
  --danger: #dc2626;
  --border: rgba(23, 23, 23, 0.1);
  --border-strong: rgba(23, 23, 23, 0.15);
  --bg-gradient-1: rgba(37, 99, 235, 0.07);
  --bg-gradient-2: rgba(99, 102, 241, 0.05);
  --surface-input: #f5f5f5;
  --surface-muted: #fafafa;
  --surface-btn: #f5f5f5;
  --surface-panel-shine: rgba(255, 255, 255, 0.9);
  --surface-toc: #fafafa;
  --surface-task: #fafafa;
  --surface-badge: #f5f5f5;
  --placeholder: #a3a3a3;
  --term-bg: rgba(37, 99, 235, 0.1);
  --term-border: rgba(37, 99, 235, 0.28);
  --term-known-bg: rgba(22, 163, 74, 0.1);
  --term-known-border: rgba(22, 163, 74, 0.35);
  --btn-accent-bg: linear-gradient(to right, #6366f1, #2563eb, #06b6d4);
  --btn-accent-border: transparent;
  --btn-accent-shadow: 0 4px 15px rgba(79, 70, 229, 0.2);
  --btn-accent-shadow-hover: 0 0 32px 6px rgba(37, 99, 235, 0.22);
  --btn-hover-border: rgba(37, 99, 235, 0.35);
  --toc-active-bg: rgba(37, 99, 235, 0.08);
  --toc-active-border: rgba(37, 99, 235, 0.35);
  --toc-hover-border: rgba(37, 99, 235, 0.22);
  --focus-border: rgba(37, 99, 235, 0.45);
  --focus-ring: rgba(37, 99, 235, 0.15);
  --modal-bg: #ffffff;
  --overlay-bg: rgba(15, 23, 42, 0.4);
  --shadow-modal: 0 20px 60px rgba(15, 23, 42, 0.14);
  --good-bg: rgba(22, 163, 74, 0.1);
  --good-border: rgba(22, 163, 74, 0.35);
  --bad-bg: rgba(220, 38, 38, 0.08);
  --bad-border: rgba(220, 38, 38, 0.35);
}

* {
  box-sizing: border-box;
}

button,
input,
select,
textarea {
  font: inherit;
}

body {
  margin: 0;
  font-family: var(--font);
  line-height: 1.6;
  background: radial-gradient(1000px 600px at 20% 0%, var(--bg-gradient-1), transparent),
    radial-gradient(900px 600px at 80% 10%, var(--bg-gradient-2), transparent),
    var(--bg);
  color: var(--text);
  transition: background-color 0.2s ease, color 0.2s ease;
}

h1,
h2,
h3 {
  font-family: var(--font-display);
  font-weight: 300;
  letter-spacing: -0.02em;
  line-height: 1.15;
}

p {
  line-height: 1.7;
}

.demoBanner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem 1rem;
  padding: 0.75rem 1.125rem;
  border-bottom: 1px solid var(--border);
  background: var(--toc-active-bg);
  color: var(--text-soft);
  font-size: 0.875rem;
}

.demoBanner strong {
  font-family: var(--font-display);
  font-weight: 400;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--accent);
}

.demoBanner__link {
  margin-left: auto;
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
}

.demoBanner__link:hover {
  text-decoration: underline;
}

body[data-demo="true"] .demo-only-hide {
  display: none !important;
}

body.glossary-hidden .sidebarGlossary,
body.glossary-hidden #glossaryPanel {
  display: none !important;
}

/* Demo reader: content-first, chapters live in the hamburger menu */
body[data-demo="true"] .layout {
  grid-template-columns: 1fr;
}

body[data-demo="true"] .sidebar {
  display: none;
}

body[data-demo="true"] .demoBanner {
  display: none;
}

/* ── Hamburger / drawer ── */
.menuToggle {
  width: 42px;
  height: 42px;
  padding: 0;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
}

.menuToggle__bar {
  display: block;
  width: 18px;
  height: 2px;
  background: currentColor;
  border-radius: 2px;
  transition: transform 0.2s ease, opacity 0.2s ease;
}

body.menu-open .menuToggle__bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

body.menu-open .menuToggle__bar:nth-child(2) {
  opacity: 0;
}

body.menu-open .menuToggle__bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.menuBackdrop {
  position: fixed;
  inset: 0;
  z-index: 80;
  background: var(--overlay-bg);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
  border: 0;
}

body.menu-open .menuBackdrop {
  opacity: 1;
  pointer-events: auto;
}

.appMenu {
  position: fixed;
  top: 0;
  right: 0;
  z-index: 90;
  width: min(22rem, 92vw);
  height: 100%;
  background: var(--panel);
  border-left: 1px solid var(--border);
  box-shadow: var(--shadow-modal);
  transform: translateX(100%);
  transition: transform 0.28s ease;
  display: flex;
  flex-direction: column;
  padding: 1rem 1.125rem 1.5rem;
  overflow: auto;
}

body.menu-open .appMenu {
  transform: translateX(0);
}

.appMenu__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 1rem;
}

.appMenu__title {
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 300;
}

.appMenu__section {
  margin-top: 1.25rem;
}

.appMenu__label {
  display: block;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--dim);
  font-weight: 600;
  margin-bottom: 0.625rem;
}

.appMenu .toc {
  gap: 6px;
}

.appMenu__themeRow {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.appMenu__themeRow .btn.is-active {
  border-color: var(--btn-accent-border);
  background: var(--btn-accent-bg);
  color: #fff;
  box-shadow: var(--btn-accent-shadow);
}

.appMenu__link {
  display: flex;
  width: 100%;
  margin-top: 0.5rem;
}

/* ── Book cover ── */
.bookCover {
  position: fixed;
  inset: 0;
  z-index: 70;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  background: var(--bg);
}

.bookCover--hidden {
  display: none;
}

.bookCover__frame {
  position: relative;
  width: min(100%, 42rem);
  max-height: min(92vh, 56rem);
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border);
  box-shadow: var(--shadow-modal);
  background: #000;
}

.bookCover__frame picture,
.bookCover__frame img {
  display: block;
  width: 100%;
  height: min(78vh, 48rem);
  object-fit: cover;
  object-position: center;
}

.bookCover__actions {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  padding: 1.25rem 1rem 1.5rem;
  background: linear-gradient(to top, rgba(0, 0, 0, 0.72), transparent);
  display: flex;
  justify-content: center;
}

.bookCover__actions .btn {
  min-width: 10rem;
}

@media (max-width: 640px) {
  .bookCover {
    padding: 0;
  }

  .bookCover__frame {
    width: 100%;
    max-height: none;
    height: 100%;
    border-radius: 0;
    border: 0;
  }

  .bookCover__frame picture,
  .bookCover__frame img {
    height: 100%;
  }
}

.brand {
  font-family: var(--font-display);
  font-size: 1.125rem;
  font-weight: 300;
  letter-spacing: -0.02em;
}

.book-title {
  color: var(--muted);
  margin-left: 12px;
  font-size: 0.875rem;
  font-weight: 400;
}

.topbar__left {
  display: flex;
  align-items: baseline;
  gap: 12px;
}

.topbar__right {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.filebtn,
.btn,
.tocBtn,
.iconBtn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-weight: 600;
  border-radius: var(--radius);
  transition: all 0.3s ease;
  white-space: nowrap;
  cursor: pointer;
}

.filebtn {
  background: var(--surface-btn);
  border: 1px solid var(--border-strong);
  padding: 0.625rem 1rem;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-soft);
  user-select: none;
  text-decoration: none;
}

.filebtn:hover {
  color: var(--text);
  border-color: var(--btn-hover-border);
}

.themeToggle {
  min-width: 4.5rem;
  justify-content: center;
}

.layout {
  display: grid;
  grid-template-columns: 0.5fr 3fr;
  gap: 16px;
  padding: 16px;
}

.sidebar {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.panel {
  background: linear-gradient(180deg, var(--surface-panel-shine), transparent 60%),
    var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 14px;
}

.panel__titleRow {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
}

.panel__title {
  margin: 0 0 10px 0;
  font-size: 1.125rem;
}

h2 {
  font-size: 1.125rem;
}

.muted {
  color: var(--muted);
  font-size: 0.875rem;
  line-height: 1.7;
}

.search,
.input,
select,
textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  font-size: 0.875rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface-input);
  color: var(--text);
  outline: none;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.search::placeholder,
.input::placeholder,
textarea::placeholder {
  color: var(--placeholder);
}

.search:focus,
.input:focus,
select:focus,
textarea:focus {
  border-color: var(--focus-border);
  box-shadow: 0 0 0 1px var(--focus-ring);
}

.toc {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.tocBtn {
  width: 100%;
  text-align: left;
  border: 1px solid transparent;
  padding: 0.75rem 1rem;
  background: var(--surface-toc);
  color: var(--text-soft);
  font-size: 0.875rem;
  font-weight: 500;
}

.tocBtn:hover {
  color: var(--text);
  border-color: var(--toc-hover-border);
}

.tocBtn--active {
  color: var(--text);
  border-color: var(--toc-active-border);
  background: var(--toc-active-bg);
}

.glossary {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 12px;
  max-height: 330px;
  overflow: auto;
  padding-right: 4px;
}

.glossaryTerm {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 10px 12px;
  background: var(--surface-muted);
  cursor: pointer;
}

.glossaryTerm:hover {
  border-color: var(--btn-hover-border);
}

.termText {
  font-weight: 600;
}

.content {
  background: var(--panel2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px;
  min-height: 600px;
}

.pageHeader h1 {
  margin: 0 0 6px 0;
  font-size: clamp(1.5rem, 3vw, 2rem);
}

.pageBody {
  margin-top: 12px;
}

.paragraph {
  line-height: 1.8;
  font-size: 1.05rem;
  white-space: pre-wrap;
  color: var(--text-soft);
  margin: 0 0 1.75rem;
}

.paragraph:last-of-type {
  margin-bottom: 0.5rem;
}

.chapterNav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  margin: 2rem 0 0.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
}

.chapterNav__label {
  font-size: 0.875rem;
  text-align: center;
  flex: 1 1 auto;
}

.chapterNav__btn {
  min-width: 7.5rem;
}

.chapterNav__btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.termLink {
  cursor: pointer;
  color: var(--text);
  background: var(--term-bg);
  border: 1px solid var(--term-border);
  padding: 1px 4px;
  border-radius: 8px;
}

.termLink--known {
  border-color: var(--term-known-border);
  background: var(--term-known-bg);
}

.taskBlock {
  border: 1px solid var(--border);
  background: var(--surface-task);
  border-radius: 14px;
  padding: 14px;
  margin-bottom: 14px;
}

.taskTitle {
  margin: 0 0 10px 0;
  font-size: 1.25rem;
}

.grid2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.btn {
  border: 1px solid var(--border-strong);
  background: var(--surface-btn);
  color: var(--text-soft);
  padding: 0.625rem 1.25rem;
  font-size: 0.875rem;
  font-weight: 500;
}

.btn:hover {
  color: var(--text);
  border-color: var(--btn-hover-border);
}

.btn--accent {
  color: #ffffff;
  border-color: transparent;
  background: var(--btn-accent-bg);
  box-shadow: var(--btn-accent-shadow);
  font-weight: 600;
}

.btn--accent:hover {
  color: #ffffff;
  border-color: transparent;
  box-shadow: var(--btn-accent-shadow-hover);
  transform: scale(1.02);
}

.btnRow {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 12px;
}

textarea {
  min-height: 90px;
  resize: vertical;
}

.modalOverlay {
  position: fixed;
  inset: 0;
  background: var(--overlay-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.modalOverlay.hidden {
  display: none;
}

.modal {
  width: min(720px, 100%);
  background: var(--modal-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: var(--shadow-modal);
}

.modal__header {
  padding: 12px 14px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.modal__title {
  font-size: 1.25rem;
  font-weight: 300;
}

.iconBtn {
  border: 1px solid var(--border-strong);
  background: var(--surface-btn);
  color: var(--text-soft);
  width: 34px;
  height: 34px;
}

.iconBtn:hover {
  color: var(--text);
  border-color: var(--btn-hover-border);
}

.modal__body {
  padding: 14px;
}

.kbdHint {
  color: var(--dim);
  font-size: 0.875rem;
  line-height: 1.7;
  margin-top: 8px;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 10px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--surface-badge);
}

.good {
  border-color: var(--good-border);
  background: var(--good-bg);
}

.bad {
  border-color: var(--bad-border);
  background: var(--bad-bg);
}

.row {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}

.small {
  font-size: 0.875rem;
  line-height: 1.7;
}

.fillBlankRow {
  margin-bottom: 14px;
}

.fillBlankHint {
  margin: 0 0 8px;
  font-style: italic;
}

.cornell {
  margin-top: 28px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

.cornell__title {
  font-size: clamp(1.25rem, 2.5vw, 1.5rem);
  margin: 0 0 8px;
}

.cornell__intro {
  margin: 0 0 16px;
  color: var(--muted);
  line-height: 1.7;
}

.cornell__grid {
  display: grid;
  grid-template-columns: 1fr 1.4fr;
  gap: 14px;
}

.cornell__field {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.cornell__field--summary {
  margin-top: 14px;
}

.cornell__label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--dim);
  font-weight: 600;
}

.cornell__input {
  min-height: 120px;
  resize: vertical;
}

.cornell__actions {
  margin-top: 14px;
}

.cornell__status {
  margin-top: 10px;
}

.cornell__status--saved {
  color: var(--accent);
}

@media (max-width: 960px) {
  .layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  .cornell__grid {
    grid-template-columns: 1fr;
  }

  .topbar__left {
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
  }

  .book-title {
    margin-left: 0;
  }
}