:root {
  color-scheme: light;
  --bg: #f5f7fb;
  --panel: #ffffff;
  --panel-soft: #eef6ff;
  --ink: #172033;
  --muted: #6a7283;
  --line: #dce4ef;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-soft: #dbeafe;
  --green: #16a34a;
  --green-soft: #dcfce7;
  --red: #dc2626;
  --red-soft: #fee2e2;
  --amber: #d97706;
  --shadow: 0 18px 45px rgba(29, 78, 216, 0.12);
  --radius-lg: 28px;
  --radius-md: 18px;
  --radius-sm: 12px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.18), transparent 32rem),
    linear-gradient(145deg, #f8fbff 0%, var(--bg) 48%, #eef4ff 100%);
}

button,
input,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem clamp(1rem, 4vw, 3rem);
  border-bottom: 1px solid rgba(220, 228, 239, 0.78);
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: blur(18px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.8rem;
  color: inherit;
  text-decoration: none;
}

.brand__mark {
  display: grid;
  width: 2.7rem;
  height: 2.7rem;
  place-items: center;
  border-radius: 1rem;
  color: #ffffff;
  font-weight: 900;
  letter-spacing: 0.04em;
  background: linear-gradient(135deg, #2563eb, #14b8a6);
  box-shadow: 0 12px 24px rgba(37, 99, 235, 0.2);
}

.brand strong,
.brand small {
  display: block;
}

.brand small {
  margin-top: 0.1rem;
  color: var(--muted);
  font-size: 0.78rem;
}

.header-nav {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.header-nav button,
.ghost-button {
  border: 1px solid var(--line);
  color: var(--ink);
  background: rgba(255, 255, 255, 0.7);
  border-radius: 999px;
  padding: 0.65rem 1rem;
  transition: 0.18s ease;
}

.header-nav button:hover,
.header-nav button.is-active,
.ghost-button:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-soft);
}

.app-shell {
  width: min(1120px, calc(100% - 2rem));
  margin: 2rem auto;
}

.app-footer {
  width: min(1120px, calc(100% - 2rem));
  margin: 1rem auto 2rem;
  color: var(--muted);
  font-size: 0.9rem;
  text-align: center;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(280px, 0.85fr);
  gap: 1.5rem;
  align-items: stretch;
}

.card {
  border: 1px solid rgba(220, 228, 239, 0.88);
  border-radius: var(--radius-lg);
  background: rgba(255, 255, 255, 0.88);
  box-shadow: var(--shadow);
}

.card__body {
  padding: clamp(1.25rem, 4vw, 2rem);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  margin: 0 0 0.8rem;
  color: var(--primary);
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  margin: 0;
  line-height: 1.08;
}

h1 {
  font-size: clamp(2.1rem, 6vw, 4.6rem);
  letter-spacing: -0.05em;
}

h2 {
  font-size: clamp(1.55rem, 3.2vw, 2.35rem);
  letter-spacing: -0.035em;
}

h3 {
  font-size: 1.05rem;
}

.lead {
  max-width: 62ch;
  margin: 1rem 0 0;
  color: var(--muted);
  font-size: 1.05rem;
  line-height: 1.65;
}

.login-form {
  display: grid;
  gap: 0.9rem;
  margin-top: 1.4rem;
}

.login-form label {
  color: var(--muted);
  font-weight: 700;
}

.login-form input {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 0.95rem 1rem;
  color: var(--ink);
  background: #ffffff;
  outline: none;
}

.login-form input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.12);
}

.primary-button {
  border: 0;
  border-radius: 999px;
  padding: 0.9rem 1.2rem;
  color: #ffffff;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), #0f766e);
  box-shadow: 0 16px 30px rgba(37, 99, 235, 0.22);
  transition: transform 0.16s ease, box-shadow 0.16s ease;
}

.primary-button:hover {
  transform: translateY(-1px);
  box-shadow: 0 18px 34px rgba(37, 99, 235, 0.28);
}

.primary-button:disabled,
.ghost-button:disabled,
.option-button:disabled {
  cursor: not-allowed;
  opacity: 0.62;
}

.error-text {
  min-height: 1.3rem;
  color: var(--red);
  font-weight: 700;
}

.feature-list {
  display: grid;
  gap: 0.85rem;
  margin: 1.25rem 0 0;
  padding: 0;
  list-style: none;
}

.feature-list li,
.mini-card {
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  padding: 1rem;
  background: #ffffff;
}

.mini-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.8rem;
  margin-top: 1.25rem;
}

.mini-card strong {
  display: block;
  font-size: 1.5rem;
}

.mini-card span {
  color: var(--muted);
  font-size: 0.9rem;
}

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

.mode-grid {
  display: grid;
  grid-template-columns: repeat(5, minmax(140px, 1fr));
  gap: 0.75rem;
  margin-top: 1rem;
}

.mode-button {
  min-height: 6rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  padding: 1rem;
  color: var(--ink);
  text-align: left;
  background: #ffffff;
  transition: 0.18s ease;
}

.mode-button strong,
.mode-button small {
  display: block;
}

.mode-button small {
  margin-top: 0.45rem;
  color: var(--muted);
}

.mode-button:hover,
.mode-button.is-active {
  border-color: var(--primary);
  background: var(--primary-soft);
  transform: translateY(-2px);
}

.quiz-layout {
  display: grid;
  grid-template-columns: minmax(0, 0.95fr) minmax(280px, 0.42fr);
  gap: 1rem;
  align-items: start;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
  margin: 1rem 0;
}

.stat {
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  padding: 1rem;
  background: #ffffff;
}

.stat strong {
  display: block;
  font-size: 1.4rem;
}

.stat span {
  color: var(--muted);
  font-size: 0.86rem;
}

.progress {
  overflow: hidden;
  height: 0.72rem;
  border-radius: 999px;
  background: #e5eaf3;
}

.progress__bar {
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--primary), #14b8a6);
  transition: width 0.28s ease;
}

.question-item {
  display: inline-flex;
  max-width: 100%;
  margin: 1.1rem 0;
  border-radius: 1.2rem;
  padding: 1rem 1.2rem;
  color: #0f172a;
  font-size: clamp(1.75rem, 6vw, 3.2rem);
  font-weight: 900;
  letter-spacing: -0.04em;
  background: linear-gradient(135deg, #eef6ff, #f8fafc);
}

.answer-section {
  margin-top: 1rem;
}

.answer-section h3 {
  margin-bottom: 0.7rem;
}

.option-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.7rem;
}

.option-grid--side {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.option-button {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 0.9rem;
  color: var(--ink);
  text-align: left;
  background: #ffffff;
  transition: 0.16s ease;
}

.option-button:hover,
.option-button.is-selected {
  border-color: var(--primary);
  background: var(--primary-soft);
}

.option-button.is-correct {
  border-color: var(--green);
  background: var(--green-soft);
}

.option-button.is-wrong {
  border-color: var(--red);
  background: var(--red-soft);
}

.feedback {
  margin-top: 1rem;
  border-radius: var(--radius-md);
  padding: 1rem;
  line-height: 1.6;
}

.feedback--correct {
  color: #14532d;
  background: var(--green-soft);
}

.feedback--wrong {
  color: #7f1d1d;
  background: var(--red-soft);
}

.actions {
  display: flex;
  gap: 0.7rem;
  align-items: center;
  flex-wrap: wrap;
  margin-top: 1rem;
}

.side-panel {
  position: sticky;
  top: 6.4rem;
}

.rule-list,
.review-list,
.notes-grid {
  display: grid;
  gap: 0.8rem;
  margin: 1rem 0 0;
  padding: 0;
  list-style: none;
}

.rule-list li {
  display: flex;
  justify-content: space-between;
  gap: 0.8rem;
  border-radius: var(--radius-sm);
  padding: 0.85rem 1rem;
  background: var(--panel-soft);
}

.pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 999px;
  padding: 0.28rem 0.65rem;
  color: var(--primary-dark);
  font-size: 0.78rem;
  font-weight: 800;
  background: var(--primary-soft);
  white-space: nowrap;
}

.pill--green {
  color: #166534;
  background: var(--green-soft);
}

.pill--red {
  color: #991b1b;
  background: var(--red-soft);
}

.review-card {
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  padding: 1rem;
  background: #ffffff;
}

.review-card h3 {
  margin-bottom: 0.55rem;
}

.review-meta {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin: 0.6rem 0;
}

.notes-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.note-card {
  border: 1px solid var(--line);
  border-radius: var(--radius-md);
  padding: 1rem;
  background: #ffffff;
}

.note-card p {
  margin: 0.55rem 0 0;
  color: var(--muted);
  line-height: 1.6;
}

.rule-banner {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.rule-banner > div {
  border-radius: var(--radius-md);
  padding: 1.1rem;
}

.rule-banner strong {
  display: block;
  font-size: 1.2rem;
}

.rule-banner small {
  display: block;
  margin-top: 0.35rem;
  line-height: 1.5;
}

.rule-banner__debit {
  color: #14532d;
  background: var(--green-soft);
}

.rule-banner__credit {
  color: #1e3a8a;
  background: var(--primary-soft);
}

.empty-state {
  border: 1px dashed #b8c3d4;
  border-radius: var(--radius-lg);
  padding: 2rem;
  color: var(--muted);
  text-align: center;
  background: rgba(255, 255, 255, 0.72);
}

@media (max-width: 920px) {
  .hero,
  .quiz-layout,
  .rule-banner {
    grid-template-columns: 1fr;
  }

  .mode-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .side-panel {
    position: static;
  }
}

@media (max-width: 640px) {
  .app-header {
    align-items: flex-start;
    flex-direction: column;
  }

  .header-nav {
    width: 100%;
  }

  .header-nav button {
    flex: 1 1 auto;
  }

  .app-shell {
    width: min(100% - 1rem, 1120px);
    margin-top: 1rem;
  }

  .card__body {
    padding: 1rem;
  }

  .mode-grid,
  .option-grid,
  .stats-grid,
  .notes-grid,
  .mini-grid {
    grid-template-columns: 1fr;
  }
}