:root {
  --student-mint: #35d5b6;
  --student-hover: #22b99d;
  --student-soft: #dcfbf5;
  --teacher-indigo: #5665ed;
  --teacher-hover: #4352d9;
  --teacher-soft: #e8eafe;
  --background: #f6f8fc;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #e5e7eb;
  --ink-soft: #eef2f7;
  --warm-note: #fff7dc;
  --warning: #946200;
  --shadow: 0 18px 45px rgba(31, 41, 55, 0.08);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--background);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
}

img {
  max-width: 100%;
  display: block;
}

a {
  color: inherit;
  text-decoration: none;
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 3px solid rgba(86, 101, 237, 0.36);
  outline-offset: 3px;
}

.container {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(246, 248, 252, 0.94);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(12px);
}

.nav {
  min-height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  letter-spacing: 0;
}

.nav-links,
.footer-links {
  display: flex;
  align-items: center;
  gap: 22px;
  color: var(--muted);
  font-size: 0.95rem;
}

.nav-links a:hover,
.footer-links a:hover {
  color: var(--teacher-hover);
}

.button {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  border: 1px solid transparent;
  border-radius: 8px;
  padding: 11px 18px;
  font-weight: 800;
  line-height: 1.2;
  transition: background 160ms ease, border-color 160ms ease, transform 160ms ease;
}

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

.button-primary {
  background: var(--teacher-indigo);
  color: #ffffff;
  box-shadow: 0 10px 25px rgba(86, 101, 237, 0.22);
}

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

.button-secondary {
  background: var(--card);
  border-color: var(--border);
  color: var(--text);
}

.button-secondary:hover {
  border-color: var(--teacher-indigo);
}

.section {
  padding: 84px 0;
}

.section-muted {
  background: var(--card);
  border-block: 1px solid var(--border);
}

.hero {
  padding-top: 92px;
  overflow: hidden;
}

.hero-inner {
  display: grid;
  gap: 42px;
}

.hero-copy {
  max-width: 860px;
}

.eyebrow {
  margin: 0 0 12px;
  color: var(--teacher-hover);
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 900px;
  margin-bottom: 22px;
  font-size: clamp(2.4rem, 6vw, 4.8rem);
  line-height: 0.98;
  letter-spacing: 0;
}

h2 {
  margin-bottom: 18px;
  font-size: clamp(1.75rem, 4vw, 2.75rem);
  line-height: 1.08;
  letter-spacing: 0;
}

h3 {
  margin-bottom: 8px;
  font-size: 1.05rem;
  line-height: 1.28;
  letter-spacing: 0;
}

.hero-lead {
  max-width: 720px;
  color: var(--muted);
  font-size: 1.2rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 28px;
}

.product-preview {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(280px, 0.8fr);
  gap: 18px;
  align-items: stretch;
  margin-top: 18px;
}

.preview-doc,
.preview-panel,
.card,
.status-card,
details {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.preview-doc {
  overflow: hidden;
  min-height: 380px;
}

.preview-toolbar {
  display: flex;
  gap: 8px;
  padding: 14px 18px;
  background: var(--ink-soft);
  border-bottom: 1px solid var(--border);
}

.preview-toolbar span {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--student-mint);
}

.preview-toolbar span:nth-child(2) {
  background: var(--teacher-indigo);
}

.preview-toolbar span:nth-child(3) {
  background: #f6c453;
}

.preview-body {
  padding: 28px;
}

.doc-line {
  width: 100%;
  height: 14px;
  margin-bottom: 14px;
  border-radius: 999px;
  background: #d9dee8;
}

.doc-line.long {
  width: 86%;
}

.doc-line.medium {
  width: 66%;
}

.doc-line.short {
  width: 48%;
}

.doc-paragraph {
  margin: 30px 0;
}

.feedback-note {
  width: min(360px, 100%);
  margin-top: 18px;
  padding: 16px;
  border-radius: 8px;
  border: 1px solid transparent;
}

.feedback-note strong,
.feedback-note span {
  display: block;
}

.feedback-note strong {
  margin-bottom: 4px;
}

.feedback-note.student {
  background: var(--student-soft);
  border-color: rgba(34, 185, 157, 0.28);
}

.feedback-note.teacher {
  margin-left: auto;
  background: var(--teacher-soft);
  border-color: rgba(86, 101, 237, 0.24);
}

.preview-panel {
  align-self: center;
  padding: 26px;
}

.panel-label {
  display: inline-flex;
  margin-bottom: 18px;
  border-radius: 999px;
  padding: 6px 10px;
  background: var(--student-soft);
  color: #0d6f60;
  font-size: 0.78rem;
  font-weight: 900;
}

.preview-panel h2 {
  font-size: 1.45rem;
}

.preview-panel ul,
.check-list,
.status-card ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.preview-panel li,
.check-list li,
.status-card li {
  position: relative;
  margin: 12px 0;
  padding-left: 28px;
}

.preview-panel li::before,
.check-list li::before,
.status-card li::before {
  position: absolute;
  left: 0;
  top: 0.1em;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--student-mint);
  color: #073d35;
  content: "✓";
  display: grid;
  place-items: center;
  font-size: 0.72rem;
  font-weight: 900;
}

.section-grid,
.split,
.safety,
.faq-layout {
  display: grid;
  grid-template-columns: 0.8fr 1.2fr;
  gap: 42px;
  align-items: start;
}

.section-intro,
.section-heading {
  max-width: 760px;
}

.section-heading {
  margin-bottom: 34px;
}

.section-intro p,
.section-heading p,
.split p,
.safety p,
.contact p,
.card p,
.feature-row p,
.status-card li,
details p {
  color: var(--muted);
}

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

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

.cards.two {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin-top: 20px;
}

.card {
  padding: 24px;
}

.feature-list {
  display: grid;
  gap: 18px;
}

.feature-row {
  display: grid;
  grid-template-columns: 48px 1fr;
  gap: 16px;
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
}

.feature-row:last-child {
  border-bottom: 0;
}

.feature-icon {
  width: 44px;
  height: 44px;
  border-radius: 8px;
  border: 1px solid var(--border);
}

.student-icon {
  background: linear-gradient(135deg, var(--student-soft), var(--student-mint));
}

.teacher-icon {
  background: linear-gradient(135deg, var(--teacher-soft), var(--teacher-indigo));
}

.mixed-icon {
  background:
    linear-gradient(135deg, var(--student-mint) 0 48%, transparent 48%),
    linear-gradient(135deg, transparent 52%, var(--teacher-indigo) 52%);
}

.steps {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 16px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.steps li {
  min-height: 240px;
  padding: 22px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.steps span {
  display: grid;
  width: 36px;
  height: 36px;
  margin-bottom: 18px;
  place-items: center;
  border-radius: 8px;
  background: var(--teacher-soft);
  color: var(--teacher-hover);
  font-weight: 900;
}

.steps p {
  color: var(--muted);
  font-size: 0.95rem;
}

.benefit-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 48px;
}

.safety {
  align-items: center;
}

.check-list {
  padding: 28px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.status-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
}

.status-card {
  padding: 26px;
  box-shadow: none;
}

.status-card h3 {
  margin-bottom: 18px;
}

.status-card.implemented {
  border-top: 5px solid var(--student-mint);
}

.status-card.planned {
  border-top: 5px solid var(--teacher-indigo);
}

.faq-layout {
  grid-template-columns: 0.7fr 1.3fr;
}

.faq-list {
  display: grid;
  gap: 14px;
}

details {
  padding: 18px 20px;
  box-shadow: none;
}

summary {
  cursor: pointer;
  color: var(--text);
  font-weight: 800;
}

details p {
  margin: 14px 0 0;
}

.contact-section {
  padding-top: 56px;
}

.contact {
  padding: 42px;
  background: var(--teacher-soft);
  border: 1px solid rgba(86, 101, 237, 0.22);
  border-radius: 8px;
}

.contact p {
  max-width: 720px;
}

.footer {
  border-top: 1px solid var(--border);
  padding: 32px 0;
  background: var(--card);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 22px;
}

.footer p {
  margin: 0;
  color: var(--muted);
}

@media (max-width: 980px) {
  .nav {
    flex-wrap: wrap;
    padding: 14px 0;
  }

  .nav-links {
    order: 3;
    width: 100%;
    justify-content: center;
  }

  .product-preview,
  .section-grid,
  .split,
  .safety,
  .faq-layout,
  .benefit-grid,
  .status-columns {
    grid-template-columns: 1fr;
  }

  .cards.three,
  .cards.two,
  .steps {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 680px) {
  .container {
    width: min(100% - 24px, 1120px);
  }

  .section {
    padding: 58px 0;
  }

  .hero {
    padding-top: 62px;
  }

  h1 {
    font-size: 2.35rem;
  }

  .hero-lead {
    font-size: 1.05rem;
  }

  .nav-links {
    overflow-x: auto;
    justify-content: flex-start;
    padding-bottom: 4px;
  }

  .nav-cta {
    display: none;
  }

  .hero-actions,
  .footer-inner,
  .footer-links {
    align-items: stretch;
    flex-direction: column;
  }

  .button {
    width: 100%;
  }

  .cards.three,
  .cards.two,
  .steps {
    grid-template-columns: 1fr;
  }

  .preview-body,
  .preview-panel,
  .card,
  .steps li,
  .contact,
  .check-list {
    padding: 20px;
  }

  .preview-doc {
    min-height: 320px;
  }
}