:root {
  --bg: #f6f8fb;
  --surface: #ffffff;
  --surface-soft: #edf4ff;
  --text: #15213a;
  --muted: #5d6b84;
  --primary: #2864ff;
  --primary-dark: #1748c8;
  --accent: #20b486;
  --warning: #fff3ce;
  --border: #dbe4f0;
  --shadow: 0 18px 50px rgba(21, 33, 58, 0.10);
  --radius: 24px;
  --radius-small: 16px;
  --reader-font-size: 1rem;
  --reader-line-height: 1.7;
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100%;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}

a {
  color: inherit;
}

button,
input,
textarea {
  font: inherit;
}

button {
  cursor: pointer;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: -10rem;
  z-index: 20;
  background: var(--text);
  color: white;
  padding: 0.75rem 1rem;
  border-radius: 999px;
}

.skip-link:focus {
  top: 1rem;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
  padding: 1rem;
  background: rgba(246, 248, 251, 0.92);
  backdrop-filter: blur(18px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  text-decoration: none;
  font-weight: 800;
  font-size: 1.25rem;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 2.3rem;
  height: 2.3rem;
  border-radius: 0.85rem;
  background: var(--primary);
  color: white;
  box-shadow: 0 10px 28px rgba(40, 100, 255, 0.25);
}

.top-tabs {
  display: flex;
  gap: 0.4rem;
  overflow-x: auto;
  padding-bottom: 0.2rem;
}

.top-tabs a,
.account-link {
  text-decoration: none;
  white-space: nowrap;
  padding: 0.72rem 0.9rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-weight: 700;
}

.top-tabs a:hover,
.account-link:hover {
  color: var(--primary);
  border-color: rgba(40, 100, 255, 0.35);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  justify-content: space-between;
}

.mode-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.65rem 0.8rem;
  border-radius: 999px;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--muted);
  font-weight: 700;
}

main {
  width: min(1180px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 1.5rem 0 3rem;
}

.hero {
  display: grid;
  gap: 1.5rem;
  align-items: center;
  padding: 2rem 0;
}

.hero h1,
.page-header h1 {
  margin: 0;
  font-size: clamp(2.1rem, 7vw, 4.8rem);
  line-height: 1.02;
  letter-spacing: -0.06em;
}

.lead {
  font-size: clamp(1.08rem, 2vw, 1.35rem);
  color: var(--muted);
  max-width: 62ch;
}

.eyebrow {
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.78rem;
  font-weight: 900;
}

.hero-actions,
.button-row {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  align-items: center;
}

.button,
.tool-button,
.side-action,
.chip {
  border: 0;
  border-radius: 999px;
  min-height: 3rem;
  padding: 0.8rem 1.1rem;
  font-weight: 800;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.button.primary {
  background: var(--primary);
  color: white;
  box-shadow: 0 14px 30px rgba(40, 100, 255, 0.25);
}

.button.primary:hover {
  background: var(--primary-dark);
}

.button.secondary,
.tool-button,
.chip {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
}

.button.small,
.tool-button {
  min-height: 2.6rem;
  padding: 0.65rem 0.9rem;
  font-size: 0.95rem;
}

.soft-note,
.notice {
  color: var(--muted);
}

.notice {
  padding: 1rem;
  border-radius: var(--radius-small);
  background: var(--warning);
  border: 1px solid #f3d88a;
  margin-bottom: 1rem;
}

.hero-card,
.card,
.price-card,
.auth-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero-card {
  padding: 1.2rem;
}

.card,
.price-card,
.auth-card {
  padding: 1.2rem;
}

.card-header,
.card-title-row,
.workspace-top {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: start;
}

.status-dot {
  width: 0.8rem;
  height: 0.8rem;
  border-radius: 50%;
  background: var(--accent);
  margin-top: 0.35rem;
}

.document-snippet,
.fake-document {
  background: #f9fbff;
  border: 1px dashed var(--border);
  border-radius: var(--radius-small);
  padding: 1rem;
}

.explain-box {
  margin-top: 1rem;
  background: var(--surface-soft);
  border-radius: var(--radius-small);
  padding: 1rem;
}

.mini-grid,
.feature-grid,
.pricing-grid,
.account-grid,
.practice-grid {
  display: grid;
  gap: 1rem;
}

.mini-grid {
  grid-template-columns: 1fr;
  margin-top: 1rem;
}

.mini-grid span {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.65rem 0.8rem;
  color: var(--muted);
  font-weight: 800;
}

.section,
.page-header,
.cta-band,
.legal-page,
.auth-page {
  padding: 2rem 0;
}

.section-heading {
  margin-bottom: 1rem;
}

.feature-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.2rem;
}

.split-section {
  display: grid;
  gap: 1rem;
}

.math-demo-card,
.cta-band {
  background: linear-gradient(135deg, #eaf2ff, #ffffff);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.4rem;
}

.pill,
.demo-badge {
  display: inline-flex;
  border-radius: 999px;
  padding: 0.35rem 0.7rem;
  background: #e8f8f1;
  color: #0c7c5a;
  font-weight: 900;
  font-size: 0.78rem;
}

.step-row,
.math-learning-preview {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  align-items: center;
}

.answer-placeholder {
  border: 1px dashed var(--primary);
  border-radius: 999px;
  padding: 0.55rem 0.85rem;
  color: var(--primary);
  font-weight: 800;
}

.site-footer {
  width: min(1180px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 2rem 0;
  color: var(--muted);
  border-top: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.site-footer nav {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.app-shell {
  display: grid;
  gap: 1rem;
}

.side-panel {
  background: var(--text);
  color: white;
  border-radius: var(--radius);
  padding: 1.2rem;
  box-shadow: var(--shadow);
}

.side-panel h1 {
  margin: 0;
}

.side-subtitle {
  color: rgba(255, 255, 255, 0.75);
}

.action-stack,
.form-stack {
  display: grid;
  gap: 0.7rem;
}

.side-action {
  width: 100%;
  justify-content: flex-start;
  background: rgba(255, 255, 255, 0.12);
  color: white;
  border: 1px solid rgba(255, 255, 255, 0.18);
}

.side-action:hover {
  background: rgba(255, 255, 255, 0.18);
}

.side-card {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: var(--radius-small);
  background: rgba(255, 255, 255, 0.10);
}

.side-card h2 {
  font-size: 1rem;
  margin-top: 0;
}

.side-card a {
  display: block;
  color: white;
  margin: 0.35rem 0;
}

.workspace {
  min-width: 0;
}

.workspace-top {
  margin-bottom: 1rem;
}

.workspace-tabs {
  display: flex;
  gap: 0.45rem;
  overflow-x: auto;
  margin-bottom: 1rem;
  padding-bottom: 0.2rem;
}

.workspace-tabs button {
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 999px;
  padding: 0.75rem 1rem;
  font-weight: 900;
  color: var(--muted);
}

.workspace-tabs button[aria-selected="true"] {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.tab-panel {
  display: none;
}

.tab-panel.is-active {
  display: block;
}

.two-column,
.document-grid {
  display: grid;
  gap: 1rem;
}

.large-input,
.text-input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-small);
  padding: 0.9rem 1rem;
  background: #fbfdff;
  color: var(--text);
}

.large-input {
  resize: vertical;
}

.text-input.compact {
  max-width: 10rem;
}

.reader-preview {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: var(--radius-small);
  background: #fbfdff;
  border: 1px solid var(--border);
  font-size: var(--reader-font-size);
  line-height: var(--reader-line-height);
}

.reader-preview.focused,
body.focus-mode .reader-preview,
body.focus-mode .fake-document {
  background: #fffdf4;
  outline: 3px solid #ffd76b;
}

.check-list,
.simple-list,
.step-list {
  padding-left: 1.2rem;
}

.check-list li,
.simple-list li,
.step-list li {
  margin: 0.45rem 0;
}

.fake-document {
  min-height: 25rem;
}

.big-math {
  font-size: 2rem;
  font-weight: 900;
}

.assist-column {
  display: grid;
  gap: 1rem;
}

.math-inline-card {
  margin-top: 1rem;
}

.math-step-area {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: var(--radius-small);
  background: var(--surface-soft);
  min-height: 7rem;
}

.math-step-area .feedback {
  margin-top: 0.75rem;
  font-weight: 800;
}

.number-line-controls {
  display: grid;
  gap: 0.75rem;
  grid-template-columns: 1fr;
}

.number-line {
  position: relative;
  min-height: 5.5rem;
  margin-top: 1rem;
  border-radius: var(--radius-small);
  background: #fbfdff;
  border: 1px solid var(--border);
  overflow: hidden;
}

.number-line-track {
  position: absolute;
  left: 1rem;
  right: 1rem;
  top: 2.65rem;
  height: 0.2rem;
  background: var(--text);
}

.number-line-mark {
  position: absolute;
  top: 1.2rem;
  transform: translateX(-50%);
  display: grid;
  place-items: center;
  gap: 0.2rem;
  font-weight: 900;
  color: var(--primary);
}

.number-line-mark::before {
  content: "";
  width: 0.85rem;
  height: 0.85rem;
  border-radius: 50%;
  background: var(--primary);
}

.number-line-label {
  position: absolute;
  top: 3.1rem;
  transform: translateX(-50%);
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 800;
}

.chip-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
}

.price-card.featured {
  border-color: rgba(40, 100, 255, 0.45);
  transform: translateY(-0.25rem);
}

.price {
  font-size: 2rem;
  font-weight: 900;
  margin: 0.4rem 0 1rem;
}

.price span {
  font-size: 1rem;
  color: var(--muted);
}

.auth-page {
  display: grid;
  place-items: center;
}

.auth-card {
  width: min(100%, 32rem);
}

.legal-page {
  display: grid;
  gap: 1rem;
}

.toast {
  position: fixed;
  left: 1rem;
  right: 1rem;
  bottom: 1rem;
  padding: 1rem;
  border-radius: var(--radius-small);
  background: var(--text);
  color: white;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(1rem);
  pointer-events: none;
  transition: 180ms ease;
  z-index: 30;
}

.toast.is-visible {
  opacity: 1;
  transform: translateY(0);
}

body.child-mode {
  --radius: 30px;
  --radius-small: 20px;
}

body.child-mode .button,
body.child-mode .tool-button,
body.child-mode .side-action,
body.child-mode .chip {
  min-height: 3.35rem;
}

@media (min-width: 720px) {
  .site-header {
    grid-template-columns: auto 1fr auto;
    align-items: center;
  }

  .header-actions {
    justify-content: end;
  }

  .hero,
  .split-section,
  .two-column {
    grid-template-columns: 1fr 1fr;
  }

  .feature-grid,
  .pricing-grid,
  .account-grid,
  .practice-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

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

  .number-line-controls {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (min-width: 1020px) {
  main {
    padding-top: 2rem;
  }

  .hero {
    grid-template-columns: 1.08fr 0.92fr;
    min-height: 68vh;
  }

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

  .pricing-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .app-shell {
    grid-template-columns: 17rem minmax(0, 1fr);
    align-items: start;
  }

  .side-panel {
    position: sticky;
    top: 7rem;
  }

  .document-grid {
    grid-template-columns: minmax(0, 1.2fr) minmax(18rem, 0.75fr) minmax(13rem, 0.45fr);
  }
}