:root {
  --bg: #f7fafc;
  --surface: #ffffff;
  --surface-soft: #eef8f5;
  --ink: #172033;
  --muted: #5c6b80;
  --line: #d8e2ee;
  --blue: #246bfd;
  --teal: #18a999;
  --yellow: #f4c542;
  --coral: #ff6b5f;
  --violet: #7657d6;
  --success: #147a57;
  --danger: #b3261e;
  --shadow: 0 18px 40px rgba(23, 32, 51, 0.12);
  --radius: 8px;
  --tap: 48px;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--ink);
  background: var(--bg);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background:
    radial-gradient(circle at top left, rgba(112, 214, 255, 0.3), transparent 30rem),
    linear-gradient(180deg, #fbfdff 0%, var(--bg) 42%, #f4fbf8 100%);
  color: var(--ink);
  font-size: 18px;
  line-height: 1.6;
}

a {
  color: var(--blue);
}

a:hover {
  color: #174dcc;
}

a:focus-visible,
button:focus-visible,
input:focus-visible,
summary:focus-visible {
  outline: 4px solid rgba(36, 107, 253, 0.32);
  outline-offset: 3px;
}

img {
  max-width: 100%;
  height: auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 1px solid rgba(216, 226, 238, 0.9);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(16px);
}

.nav-wrap,
.container,
.footer-inner {
  width: min(1100px, calc(100% - 32px));
  margin: 0 auto;
}

.nav-wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: 76px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--ink);
  font-weight: 900;
  text-decoration: none;
  letter-spacing: 0;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius);
  background: var(--ink);
  color: #ffffff;
  font-size: 1.2rem;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
}

.nav-links a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 8px 12px;
  border-radius: var(--radius);
  color: var(--ink);
  font-weight: 750;
  text-decoration: none;
}

.nav-links a:hover,
.nav-links a[aria-current="page"] {
  background: #edf4ff;
  color: #174dcc;
}

main {
  padding: 34px 0 52px;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(320px, 0.95fr);
  align-items: center;
  gap: 38px;
  min-height: min(680px, calc(100vh - 96px));
  padding: 24px 0 44px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 14px;
  color: #0f6953;
  font-weight: 850;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.82rem;
}

h1,
h2,
h3 {
  line-height: 1.12;
  letter-spacing: 0;
}

h1 {
  margin: 0;
  max-width: 780px;
  font-size: clamp(2.25rem, 7vw, 4.9rem);
}

h2 {
  margin: 0 0 16px;
  font-size: clamp(1.7rem, 4vw, 2.55rem);
}

h3 {
  margin: 0 0 8px;
  font-size: 1.28rem;
}

.lead {
  margin: 18px 0 0;
  max-width: 680px;
  color: var(--muted);
  font-size: clamp(1.05rem, 2vw, 1.24rem);
}

.hero-actions,
.section-actions,
.lesson-nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-top: 26px;
}

.hero-visual img {
  display: block;
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.hero > *,
.lesson-layout > *,
.card,
.panel,
.quiz,
.task-list {
  min-width: 0;
}

.button,
button.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  min-height: var(--tap);
  padding: 12px 18px;
  border: 2px solid transparent;
  border-radius: var(--radius);
  background: var(--blue);
  color: #ffffff;
  font: inherit;
  font-weight: 850;
  text-decoration: none;
  cursor: pointer;
  box-shadow: 0 10px 22px rgba(36, 107, 253, 0.18);
}

.button:hover {
  background: #174dcc;
  color: #ffffff;
}

.button.secondary {
  border-color: var(--line);
  background: #ffffff;
  color: var(--ink);
  box-shadow: none;
}

.button.secondary:hover {
  border-color: #bfd1e7;
  background: #f7fbff;
  color: var(--ink);
}

.button.success {
  background: var(--teal);
  box-shadow: 0 10px 22px rgba(24, 169, 153, 0.18);
}

.button.success:hover {
  background: #117f72;
}

.button.danger {
  background: #ffffff;
  border-color: #ffc8c3;
  color: var(--danger);
  box-shadow: none;
}

.button.danger:hover {
  background: #fff2f1;
  color: var(--danger);
}

.section {
  padding: 42px 0;
}

.section-header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 20px;
}

.section-header p {
  max-width: 700px;
  margin: 0;
  color: var(--muted);
}

.grid {
  display: grid;
  gap: 18px;
}

.lesson-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.card,
.panel,
.quiz,
.task-list,
.callout,
.hint-box,
.score-band {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: 0 8px 24px rgba(23, 32, 51, 0.06);
}

.card {
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-height: 100%;
  padding: 20px;
}

.card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.lesson-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: var(--radius);
  background: #edf4ff;
  color: #174dcc;
  font-weight: 900;
}

.status-pill,
.difficulty,
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 32px;
  padding: 4px 10px;
  border-radius: 999px;
  background: #f1f5f9;
  color: #334155;
  font-size: 0.88rem;
  font-weight: 800;
}

.status-pill.complete {
  background: #dcfce7;
  color: #166534;
}

.meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: auto;
  color: var(--muted);
  font-size: 0.95rem;
}

.lesson-page .hero {
  grid-template-columns: 1fr;
  min-height: auto;
  padding-bottom: 20px;
}

.lesson-hero-panel {
  padding: 26px;
  border-left: 8px solid var(--yellow);
  background: #fffaf0;
}

.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 290px;
  align-items: start;
  gap: 24px;
}

.lesson-main {
  display: grid;
  gap: 20px;
}

.lesson-sidebar {
  position: sticky;
  top: 96px;
  display: grid;
  gap: 14px;
}

.panel {
  padding: 22px;
}

.panel > :first-child {
  margin-top: 0;
}

.panel > :last-child {
  margin-bottom: 0;
}

.two-column {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.keyword-list,
.outcome-list {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 0;
  margin: 0;
  list-style: none;
}

.keyword-list li,
.outcome-list li {
  border-radius: var(--radius);
  background: #eef8f5;
  padding: 9px 12px;
  color: #0f6953;
  font-weight: 800;
}

.plain-list {
  padding-left: 1.2rem;
  margin: 0;
}

.plain-list li + li {
  margin-top: 8px;
}

.quiz {
  display: grid;
  gap: 18px;
  padding: 22px;
}

.quiz-question {
  display: grid;
  gap: 12px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fbfdff;
}

.quiz-question p {
  margin: 0;
  font-weight: 850;
}

.quiz-options {
  display: grid;
  gap: 10px;
}

.quiz-option {
  width: 100%;
  min-height: var(--tap);
  padding: 12px 14px;
  border: 2px solid #cbd8e7;
  border-radius: var(--radius);
  background: #ffffff;
  color: var(--ink);
  font: inherit;
  font-weight: 700;
  text-align: left;
  cursor: pointer;
}

.quiz-option:hover {
  border-color: var(--blue);
  background: #f7fbff;
}

.quiz-option.correct {
  border-color: #16a34a;
  background: #dcfce7;
}

.quiz-option.incorrect {
  border-color: #ef4444;
  background: #fee2e2;
}

.quiz-option:disabled {
  cursor: default;
}

.quiz-feedback {
  min-height: 28px;
  margin: 0;
  color: var(--muted);
  font-weight: 750;
}

.quiz-score {
  display: inline-flex;
  width: fit-content;
  min-height: 40px;
  align-items: center;
  border-radius: var(--radius);
  padding: 7px 12px;
  background: #172033;
  color: #ffffff;
  font-weight: 900;
}

.task-list {
  display: grid;
  gap: 8px;
  padding: 12px;
}

.task-item {
  display: grid;
  grid-template-columns: 32px 1fr;
  gap: 10px;
  align-items: start;
  padding: 10px;
  border-radius: var(--radius);
}

.task-item:hover {
  background: #f7fbff;
}

.task-checkbox {
  width: 24px;
  height: 24px;
  margin-top: 4px;
  accent-color: var(--teal);
}

.progress-meter {
  height: 12px;
  overflow: hidden;
  border-radius: 999px;
  background: #e2e8f0;
}

.progress-meter span {
  display: block;
  width: 0%;
  height: 100%;
  background: linear-gradient(90deg, var(--teal), var(--blue));
  transition: width 180ms ease;
}

.callout {
  padding: 18px;
  border-left: 6px solid var(--teal);
  background: #f4fbf8;
}

.callout.warning {
  border-left-color: var(--coral);
  background: #fff6f5;
}

.hint-box {
  overflow: hidden;
}

.hint-box + .hint-box {
  margin-top: 12px;
}

.hint-box summary {
  min-height: var(--tap);
  padding: 13px 16px;
  font-weight: 850;
  cursor: pointer;
}

.hint-box div {
  padding: 0 16px 16px;
  color: var(--muted);
}

.score-band {
  padding: 18px;
  background: #fbfdff;
}

.score-band strong {
  color: var(--blue);
}

.parents-layout {
  display: grid;
  gap: 20px;
}

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

.site-footer {
  border-top: 1px solid var(--line);
  background: #ffffff;
  color: var(--muted);
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 26px 0;
  font-size: 0.95rem;
}

.footer-inner p {
  margin: 0;
}

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

@media (max-width: 900px) {
  .hero,
  .lesson-layout {
    grid-template-columns: 1fr;
  }

  .hero {
    min-height: auto;
  }

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

  .lesson-sidebar {
    position: static;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  body {
    font-size: 16px;
    overflow-x: hidden;
  }

  .nav-wrap {
    align-items: flex-start;
    flex-direction: column;
    gap: 10px;
    padding: 12px 0;
  }

  .nav-links {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    justify-content: stretch;
    gap: 6px;
    width: 100%;
  }

  .nav-links a {
    justify-content: center;
    min-width: 0;
    padding-right: 6px;
    padding-left: 6px;
  }

  main {
    padding-top: 18px;
  }

  .hero {
    gap: 24px;
    padding-top: 10px;
  }

  h1 {
    max-width: 100%;
    font-size: clamp(2.05rem, 10vw, 2.45rem);
    overflow-wrap: anywhere;
  }

  .lesson-grid,
  .summary-grid,
  .two-column,
  .lesson-sidebar {
    grid-template-columns: 1fr;
  }

  .section-header {
    align-items: flex-start;
    flex-direction: column;
  }

  .card,
  .panel,
  .quiz {
    padding: 18px;
  }

  .hero-actions .button,
  .lesson-nav .button,
  .section-actions .button {
    width: 100%;
  }
}