:root {
  --bg: #ffffff;
  --ink: #111111;
  --muted: #6b7280;
  --line: #e5e7eb;
  --card: #ffffff;
  --accent: #1d4ed8;
  --accent-soft: #eff6ff;
  --danger: #b42318;
  --danger-soft: #fef3f2;
  --success: #067647;
  --success-soft: #ecfdf3;
  --shadow: 0 10px 30px rgba(17, 17, 17, 0.06);
  --radius: 12px;
  --max: 1080px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.55;
  min-height: 100vh;
}

a {
  color: inherit;
}

img {
  max-width: 100%;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}

.header-inner,
.page,
.hero {
  width: min(var(--max), calc(100% - 32px));
  margin: 0 auto;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 68px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  font-weight: 700;
  font-size: 1.2rem;
  letter-spacing: -0.03em;
}

.nav {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.nav .install-button {
  min-height: 38px;
  padding: 8px 12px;
}

.nav a {
  text-decoration: none;
  padding: 8px 12px;
  border-radius: 10px;
  color: var(--muted);
  transition: background 0.2s ease, color 0.2s ease;
}

.nav a:hover,
.nav a.is-active {
  color: var(--ink);
  background: #f3f4f6;
}

.page {
  padding: 32px 0 72px;
}

.hero {
  padding: 48px 0 24px;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 13px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin: 0 0 12px;
}

h1 {
  font-size: clamp(2rem, 5vw, 3.4rem);
}

.lede {
  color: var(--muted);
  font-size: 1.1rem;
  max-width: 42ch;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 16px;
  border-radius: 12px;
  border: 1px solid transparent;
  background: transparent;
  color: var(--ink);
  text-decoration: none;
  font: inherit;
  cursor: pointer;
  transition: transform 0.15s ease, background 0.2s ease, border-color 0.2s ease;
}

.button:hover {
  transform: translateY(-1px);
}

.button:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
}

.button-primary {
  background: var(--ink);
  color: #fff;
}

.button-secondary {
  border-color: var(--line);
  background: #fff;
}

.button-danger {
  background: var(--danger-soft);
  color: var(--danger);
  border-color: #fecdca;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 20px;
}

.stats-grid,
.card-grid,
.library-grid {
  display: grid;
  gap: 16px;
}

.stats-grid {
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  margin: 32px 0;
}

.stat-card,
.reviewer-card,
.library-card,
.panel-card,
.form-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.stat-card,
.reviewer-card,
.library-card,
.form-card,
.panel-card {
  padding: 20px;
}

.stat-value {
  font-size: 2.4rem;
  font-weight: 700;
  letter-spacing: -0.04em;
}

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

.reviewer-card {
  text-decoration: none;
  display: block;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.reviewer-card:hover {
  transform: translateY(-2px);
  border-color: #d1d5db;
}

.reviewer-card h3,
.library-card h2 {
  font-size: 1.15rem;
}

.reviewer-card p,
.library-card p {
  color: var(--muted);
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.meta {
  color: var(--muted);
  font-size: 0.92rem;
}

.empty-copy,
.device-note {
  color: var(--muted);
}

.device-note {
  font-size: 0.92rem;
  margin-top: 24px;
}

.form-card label,
.field-label {
  display: block;
  font-weight: 600;
  margin-bottom: 8px;
}

input[type="text"],
input[type="search"],
textarea {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px 14px;
  font: inherit;
  color: var(--ink);
  background: #fff;
}

textarea {
  min-height: 280px;
  resize: vertical;
}

.field {
  margin-bottom: 18px;
}

.char-count {
  color: var(--muted);
  font-size: 0.9rem;
  margin: 8px 0 0;
}

.alert {
  margin: 16px 0 0;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--line);
}

.alert.is-error {
  background: var(--danger-soft);
  color: #7a271a;
  border-color: #fecdca;
}

.alert.is-success {
  background: var(--success-soft);
  color: var(--success);
}

.library-toolbar {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: end;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.library-grid {
  grid-template-columns: 1fr;
}

.library-card {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: start;
}

.card-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  min-width: 220px;
}

.tabs {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin: 24px 0;
}

.tabs button {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 999px;
  min-height: 40px;
  padding: 8px 14px;
  font: inherit;
  cursor: pointer;
}

.tabs button.is-active {
  background: var(--ink);
  color: #fff;
  border-color: var(--ink);
}

.flashcard-wrap {
  perspective: 1200px;
}

.flashcard {
  width: 100%;
  min-height: 280px;
  border: 0;
  padding: 0;
  background: transparent;
  cursor: pointer;
}

.flashcard-inner {
  position: relative;
  min-height: 280px;
  transform-style: preserve-3d;
  transition: transform 0.45s ease;
}

.flashcard.is-flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.flashcard-face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  box-shadow: var(--shadow);
  backface-visibility: hidden;
  text-align: center;
  font-size: 1.25rem;
}

.flashcard-back {
  transform: rotateY(180deg);
}

.quiz-question {
  font-size: 1.4rem;
}

.quiz-options {
  border: 0;
  padding: 0;
  margin: 0 0 16px;
  display: grid;
  gap: 10px;
}

.quiz-option {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px;
  cursor: pointer;
  transition: border-color 0.2s ease, background 0.2s ease;
}

.quiz-option.is-selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.quiz-option.is-correct {
  border-color: #abefc6;
  background: var(--success-soft);
}

.quiz-option.is-incorrect {
  border-color: #fecdca;
  background: var(--danger-soft);
}

.quiz-option input {
  margin-top: 4px;
}

.quiz-feedback {
  padding: 14px;
  border-radius: 12px;
  margin-bottom: 12px;
}

.quiz-feedback.is-correct {
  background: var(--success-soft);
}

.quiz-feedback.is-incorrect {
  background: var(--danger-soft);
}

.quiz-complete {
  text-align: center;
  padding: 24px 0;
}

.quiz-percent {
  font-size: 2rem;
  font-weight: 700;
}

.modal[hidden],
.loading[hidden],
[hidden] {
  display: none !important;
}

.modal,
.loading {
  position: fixed;
  inset: 0;
  background: rgba(17, 17, 17, 0.4);
  display: grid;
  place-items: center;
  z-index: 40;
  padding: 16px;
}

.modal-card,
.loading-card {
  width: min(440px, 100%);
  background: #fff;
  border-radius: 14px;
  padding: 24px;
  box-shadow: var(--shadow);
}

.spinner {
  width: 28px;
  height: 28px;
  border: 3px solid var(--line);
  border-top-color: var(--ink);
  border-radius: 50%;
  margin: 0 auto 12px;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@media (max-width: 720px) {
  .library-card,
  .header-inner {
    flex-direction: column;
    align-items: stretch;
  }

  .header-inner {
    gap: 10px;
    padding: 14px 0 12px;
  }

  .brand {
    align-self: center;
    position: relative;
    padding-bottom: 5px;
    font-family: Georgia, "Times New Roman", serif;
    font-size: 1.45rem;
    letter-spacing: 0;
  }

  .brand::after {
    position: absolute;
    right: 0;
    bottom: 0;
    left: 0;
    height: 3px;
    border-radius: 99px;
    background: var(--accent);
    content: "";
  }

  .nav {
    justify-content: center;
  }

  .card-actions .button,
  .button-row .button {
    width: 100%;
  }

  .flashcard-inner,
  .flashcard {
    min-height: 240px;
  }
}