/* Variables */
:root {
  --color-bg: #f5f7fb;
  --color-bg-strong: #e9eef8;
  --color-surface: rgba(255, 255, 255, 0.8);
  --color-surface-strong: #ffffff;
  --color-text: #102033;
  --color-text-soft: #5b6a80;
  --color-accent: #0f172a;
  --color-accent-strong: #2563eb;
  --color-accent-soft: rgba(37, 99, 235, 0.1);
  --color-border: rgba(16, 32, 51, 0.1);
  --shadow-lg: 0 28px 80px rgba(15, 23, 42, 0.12);
  --shadow-md: 0 18px 40px rgba(15, 23, 42, 0.1);
  --shadow-sm: 0 8px 20px rgba(15, 23, 42, 0.08);
  --radius-xl: 32px;
  --radius-lg: 24px;
  --radius-md: 18px;
  --radius-sm: 14px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;
  --space-7: 3rem;
  --space-8: 4rem;
  --page-width: 78rem;
  --font-body: "DM Sans", "Segoe UI", system-ui, sans-serif;
  --font-display: "Space Grotesk", "DM Sans", "Segoe UI", system-ui, sans-serif;
  --transition: 180ms ease;
}

/* Reset / Base */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 20rem;
  font-family: var(--font-body);
  line-height: 1.7;
  color: var(--color-text);
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.12), transparent 28%),
    linear-gradient(180deg, #fbfcff 0%, var(--color-bg) 45%, var(--color-bg-strong) 100%);
}

h1,
h2,
h3,
p,
ul {
  margin: 0;
}

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

pre,
code {
  font-family:
    "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

::selection {
  background: rgba(37, 99, 235, 0.16);
}

:focus-visible {
  outline: 3px solid rgba(37, 99, 235, 0.3);
  outline-offset: 3px;
}

/* Layout */
.page-shell {
  width: min(calc(100% - 1.5rem), var(--page-width));
  margin-inline: auto;
  padding: var(--space-5) 0 var(--space-8);
}

.site-header {
  margin-bottom: var(--space-6);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  margin-bottom: var(--space-5);
  padding: 0.9rem 1.1rem;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.72);
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(14px);
}

.topbar__links {
  display: none;
  gap: var(--space-4);
  color: var(--color-text-soft);
  font-weight: 500;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
}

.brand__mark {
  display: inline-grid;
  place-items: center;
  width: 2.5rem;
  height: 2.5rem;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--color-accent-strong), #60a5fa);
  color: #ffffff;
  box-shadow: 0 10px 24px rgba(37, 99, 235, 0.28);
}

.brand__text {
  font-family: var(--font-display);
}

.hero {
  display: grid;
  gap: var(--space-5);
  padding: clamp(1.5rem, 4vw, 3.5rem);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.86), rgba(255, 255, 255, 0.74));
  box-shadow: var(--shadow-lg);
  backdrop-filter: blur(16px);
}

.hero__content {
  display: grid;
  gap: var(--space-4);
}

.eyebrow,
.section-heading__eyebrow {
  display: inline-flex;
  width: fit-content;
  align-items: center;
  padding: 0.55rem 0.9rem;
  border-radius: 999px;
  background: var(--color-accent-soft);
  color: var(--color-accent-strong);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.hero__title {
  max-width: 12ch;
  font-family: var(--font-display);
  font-size: clamp(2.6rem, 7vw, 5.5rem);
  line-height: 0.98;
  letter-spacing: -0.04em;
}

.hero__lead,
.section-heading p {
  max-width: 58rem;
  color: var(--color-text-soft);
  font-size: 1.05rem;
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.hero__panel {
  display: grid;
  gap: var(--space-3);
}

.main-layout {
  display: grid;
  gap: var(--space-5);
}

.sidebar {
  display: none;
}

.content {
  display: grid;
  gap: var(--space-6);
}

.section {
  display: grid;
  gap: var(--space-5);
}

.section-heading {
  display: grid;
  gap: var(--space-3);
}

.section-heading h2 {
  max-width: 15ch;
  font-family: var(--font-display);
  font-size: clamp(1.9rem, 4vw, 3rem);
  line-height: 1.02;
  letter-spacing: -0.03em;
}

/* Components */
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 3rem;
  padding: 0.85rem 1.2rem;
  border-radius: 999px;
  font-weight: 700;
  transition:
    transform var(--transition),
    box-shadow var(--transition),
    background-color var(--transition);
}

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

.button--primary {
  background: linear-gradient(135deg, var(--color-accent), #1e293b);
  color: #ffffff;
  box-shadow: 0 14px 28px rgba(15, 23, 42, 0.18);
}

.button--secondary {
  background: rgba(255, 255, 255, 0.72);
  border: 1px solid var(--color-border);
  color: var(--color-text);
}

.metric-card,
.lesson-card,
.example-card,
.feature-panel,
.practice-card,
.sidebar__card {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.92), rgba(255, 255, 255, 0.8));
  box-shadow: var(--shadow-md);
}

.metric-card {
  padding: var(--space-4);
}

.metric-card__label {
  display: block;
  margin-bottom: var(--space-2);
  color: var(--color-text-soft);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.metric-card__value {
  font-size: 1rem;
}

.card-grid,
.feature-grid,
.practice-grid {
  display: grid;
  gap: var(--space-4);
}

.lesson-card,
.feature-panel,
.practice-card {
  padding: var(--space-5);
}

.lesson-card {
  display: grid;
  gap: var(--space-3);
}

.lesson-card h3,
.example-card h3,
.feature-panel h3,
.practice-card h3 {
  font-size: 1.12rem;
  line-height: 1.2;
}

.lesson-card p,
.feature-panel p,
.practice-card p {
  color: var(--color-text-soft);
}

.lesson-card--accent {
  background:
    linear-gradient(180deg, rgba(37, 99, 235, 0.08), rgba(255, 255, 255, 0.88)),
    var(--color-surface-strong);
}

.example-stack {
  display: grid;
  gap: var(--space-4);
}

.example-card {
  overflow: hidden;
}

.example-card__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: 1rem 1.2rem;
  border-bottom: 1px solid rgba(16, 32, 51, 0.08);
  background: rgba(16, 32, 51, 0.03);
}

.example-card__header span {
  color: var(--color-accent-strong);
  font-size: 0.9rem;
  font-weight: 700;
}

.code-block {
  margin: 0;
  padding: 1.25rem;
  overflow-x: auto;
  background: #0f172a;
  color: #dbeafe;
  font-size: 0.92rem;
  line-height: 1.7;
}

.check-list {
  display: grid;
  gap: var(--space-2);
  padding-left: 1.1rem;
  color: var(--color-text-soft);
}

.practice-card {
  position: relative;
  display: grid;
  gap: var(--space-3);
}

.practice-card__index {
  color: rgba(37, 99, 235, 0.42);
  font-family: var(--font-display);
  font-size: 2rem;
  font-weight: 700;
  line-height: 1;
}

.sidebar__card {
  position: sticky;
  top: 1rem;
  display: grid;
  gap: var(--space-3);
  padding: var(--space-5);
}

.sidebar__title {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
}

.sidebar__link {
  color: var(--color-text-soft);
  transition: color var(--transition), transform var(--transition);
}

.sidebar__link:hover,
.topbar__links a:hover {
  color: var(--color-accent-strong);
  transform: translateX(2px);
}

/* Utilities */
.feature-panel,
.practice-card,
.lesson-card,
.metric-card {
  transition:
    transform var(--transition),
    box-shadow var(--transition),
    border-color var(--transition);
}

.feature-panel:hover,
.practice-card:hover,
.lesson-card:hover,
.metric-card:hover {
  transform: translateY(-2px);
  border-color: rgba(37, 99, 235, 0.18);
  box-shadow: 0 18px 36px rgba(15, 23, 42, 0.12);
}

/* Responsive */
@media (min-width: 700px) {
  .topbar__links {
    display: flex;
  }

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

@media (min-width: 980px) {
  .page-shell {
    width: min(calc(100% - 2.5rem), var(--page-width));
    padding-top: var(--space-6);
  }

  .hero {
    grid-template-columns: minmax(0, 1.5fr) minmax(18rem, 0.8fr);
    align-items: start;
  }

  .main-layout {
    grid-template-columns: 16rem minmax(0, 1fr);
    align-items: start;
  }

  .sidebar {
    display: block;
  }

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

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

@media (max-width: 699px) {
  .page-shell {
    width: min(calc(100% - 1rem), var(--page-width));
    padding-bottom: var(--space-6);
  }

  .topbar {
    border-radius: var(--radius-lg);
  }
}