/* ==========================================================================
   Tarn — style.css
   Single stylesheet. Zero external dependencies.
   ========================================================================== */

/* --- Custom Properties --- */
:root {
  /* Colors */
  --color-deep-tarn: #1C3A4B;
  --color-deep-tarn-hover: #244B5F;
  --color-stone: #4A5568;
  --color-mist: #E8ECEF;
  --color-snow: #FAFBFC;
  --color-current-day: #2D6A4F;
  --color-white: #FFFFFF;
  --color-divider: #E2E8F0;
  --color-code-bg: #F1F5F9;
  --color-caption: #6B7280;
  --color-footer-text: #A8C5D1;
  --color-alert: #DC2626;

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'SF Mono', 'Cascadia Code', monospace;

  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-4xl: 96px;
  --space-5xl: 128px;

  /* Radii */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;

  /* Widths */
  --content-width: 720px;
  --page-width: 1200px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1), 0 2px 4px rgba(0, 0, 0, 0.06);

  /* Font sizes (desktop) */
  --text-hero: 48px;
  --text-h1: 36px;
  --text-h2: 28px;
  --text-h3: 22px;
  --text-h4: 18px;
  --text-body: 17px;
  --text-small: 14px;
  --text-code: 14px;
  --text-code-inline: 15px;
  --text-nav: 15px;
  --text-button: 15px;
}

/* --- Fonts --- */
@font-face {
  font-family: 'Inter';
  src: url('../fonts/Inter-Regular.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Inter';
  src: url('../fonts/Inter-Medium.woff2') format('woff2');
  font-weight: 500;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Inter';
  src: url('../fonts/Inter-SemiBold.woff2') format('woff2');
  font-weight: 600;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Inter';
  src: url('../fonts/Inter-Bold.woff2') format('woff2');
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'JetBrains Mono';
  src: url('../fonts/JetBrainsMono-Regular.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

/* --- Reset --- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: 100%;
  -moz-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-body);
  font-weight: 400;
  line-height: 1.7;
  color: var(--color-stone);
  background-color: var(--color-snow);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: var(--color-deep-tarn);
  text-decoration: none;
  transition: color 150ms ease;
}

a:hover {
  color: var(--color-current-day);
  text-decoration: underline;
}

ul, ol {
  list-style: none;
}

/* --- Skip Link --- */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  background: var(--color-deep-tarn);
  color: var(--color-white);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  font-size: var(--text-small);
  font-weight: 600;
  z-index: 1000;
  transition: top 150ms ease;
}

.skip-link:focus {
  top: var(--space-sm);
  text-decoration: none;
  color: var(--color-white);
}

/* --- Focus --- */
:focus-visible {
  outline: 2px solid var(--color-deep-tarn);
  outline-offset: 2px;
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-deep-tarn);
  font-weight: 600;
}

h1 {
  font-size: var(--text-h1);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.015em;
}

h2 {
  font-size: var(--text-h2);
  line-height: 1.25;
  letter-spacing: -0.01em;
}

h3 {
  font-size: var(--text-h3);
  line-height: 1.3;
}

h4 {
  font-size: var(--text-h4);
  line-height: 1.4;
}

p {
  max-width: 65ch;
}

strong {
  font-weight: 600;
}

small, .text-small {
  font-size: var(--text-small);
  line-height: 1.5;
}

.text-caption {
  font-size: var(--text-small);
  color: var(--color-caption);
  letter-spacing: 0.01em;
}

/* --- Layout --- */
.container {
  width: 100%;
  max-width: var(--page-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.container--narrow {
  max-width: var(--content-width);
  margin: 0 auto;
}

/* --- Utilities --- */
.centered-actions {
  display: flex;
  justify-content: center;
  margin-top: var(--space-xl);
}

.download-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
  justify-content: center;
}

.download-note {
  text-align: center;
  margin-top: var(--space-lg);
}

.mb-lg {
  margin-bottom: var(--space-lg);
}

/* Blog index page */
.blog-index-header {
  padding-bottom: var(--space-xl);
}

.blog-list--padded {
  padding: 0 var(--space-lg) var(--space-3xl);
}

/* --- Navigation --- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-white);
  border-bottom: 1px solid var(--color-divider);
  height: 64px;
  transition: box-shadow 150ms ease;
}

.nav.scrolled {
  box-shadow: var(--shadow-sm);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  max-width: var(--page-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.nav__brand {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  text-decoration: none;
  color: var(--color-deep-tarn);
}

.nav__brand:hover {
  text-decoration: none;
  color: var(--color-deep-tarn);
}

.nav__icon {
  width: 28px;
  height: 28px;
  border-radius: var(--radius-sm);
}

.nav__wordmark {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

.nav__link {
  font-size: var(--text-nav);
  font-weight: 500;
  color: var(--color-stone);
  text-decoration: none;
  letter-spacing: 0.01em;
  transition: color 150ms ease;
}

.nav__link:hover,
.nav__link--active {
  color: var(--color-deep-tarn);
  text-decoration: none;
}

/* Mobile nav toggle */
.nav__toggle {
  display: none;
  background: none;
  border: none;
  padding: var(--space-sm);
  cursor: pointer;
  color: var(--color-deep-tarn);
}

.nav__toggle svg {
  width: 24px;
  height: 24px;
}

.nav__toggle-close {
  display: none;
}

/* --- Hero --- */
.hero {
  padding: var(--space-5xl) 0 var(--space-4xl);
  text-align: center;
  background: var(--color-snow);
}

.hero__icon {
  width: 32px;
  height: 32px;
  margin: 0 auto var(--space-lg);
  opacity: 0.4;
  border-radius: var(--radius-sm);
}

.hero__title {
  font-size: var(--text-hero);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--color-deep-tarn);
  margin-bottom: var(--space-lg);
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

.hero__subtitle {
  font-size: 20px;
  font-weight: 400;
  color: var(--color-stone);
  line-height: 1.6;
  margin-bottom: var(--space-xl);
  max-width: 540px;
  margin-left: auto;
  margin-right: auto;
}

.hero__actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  flex-wrap: wrap;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  font-family: var(--font-sans);
  font-size: var(--text-button);
  font-weight: 600;
  letter-spacing: 0.01em;
  padding: 12px 24px;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  text-decoration: none;
  transition: background-color 150ms ease, color 150ms ease, border-color 150ms ease;
  min-width: 120px;
}

.btn:hover {
  text-decoration: none;
}

.btn--primary {
  background: var(--color-deep-tarn);
  color: var(--color-white);
}

.btn--primary:hover {
  background: var(--color-deep-tarn-hover);
  color: var(--color-white);
}

.btn--secondary {
  background: transparent;
  color: var(--color-deep-tarn);
  border: 1.5px solid var(--color-deep-tarn);
}

.btn--secondary:hover {
  background: rgba(28, 58, 75, 0.05);
  color: var(--color-deep-tarn);
}

.btn--ghost {
  background: transparent;
  color: var(--color-stone);
  padding: 12px 16px;
  min-width: auto;
}

.btn--ghost:hover {
  text-decoration: underline;
}

/* --- Sections --- */
.section {
  padding: var(--space-4xl) 0;
}

.section--white {
  background: var(--color-white);
}

.section--snow {
  background: var(--color-snow);
}

.section--mist {
  background: var(--color-mist);
}

.section--dark {
  background: var(--color-deep-tarn);
  color: var(--color-footer-text);
}

.section__header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.section__title {
  margin-bottom: var(--space-md);
}

.section__subtitle {
  font-size: 18px;
  color: var(--color-stone);
  max-width: 540px;
  margin: 0 auto;
}

/* --- Feature Blocks --- */
.features {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-2xl);
}

.feature {
  text-align: left;
}

.feature__icon {
  width: 24px;
  height: 24px;
  color: var(--color-deep-tarn);
  margin-bottom: var(--space-md);
}

.feature__title {
  font-size: var(--text-h4);
  font-weight: 600;
  color: var(--color-deep-tarn);
  margin-bottom: var(--space-sm);
}

.feature__text {
  font-size: 16px;
  color: var(--color-stone);
  line-height: 1.6;
}

/* --- Steps --- */
.steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-2xl);
  counter-reset: step;
}

.step {
  text-align: center;
  counter-increment: step;
}

.step__number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--color-mist);
  color: var(--color-deep-tarn);
  font-size: 20px;
  font-weight: 700;
  margin-bottom: var(--space-md);
}

.step__title {
  font-size: var(--text-h4);
  font-weight: 600;
  color: var(--color-deep-tarn);
  margin-bottom: var(--space-sm);
}

.step__text {
  font-size: 16px;
  color: var(--color-stone);
  line-height: 1.6;
  max-width: 300px;
  margin: 0 auto;
}

/* --- Comparison Table --- */
.comparison {
  max-width: 720px;
  margin: 0 auto;
}

.comparison table {
  width: 100%;
  border-collapse: collapse;
  font-size: 16px;
}

.comparison th,
.comparison td {
  text-align: left;
  padding: var(--space-md) var(--space-lg);
  border-bottom: 1px solid var(--color-divider);
}

.comparison thead th {
  background: var(--color-mist);
  color: var(--color-deep-tarn);
  font-weight: 600;
  font-size: var(--text-small);
  letter-spacing: 0.01em;
}

.comparison thead th:first-child {
  border-radius: var(--radius-md) 0 0 0;
}

.comparison thead th:last-child {
  border-radius: 0 var(--radius-md) 0 0;
}

.comparison tbody td {
  color: var(--color-stone);
}

.comparison tbody td:last-child {
  color: var(--color-deep-tarn);
  font-weight: 500;
}

.comparison tbody tr:last-child td {
  border-bottom: none;
}

/* --- Callout --- */
.callout {
  background: var(--color-mist);
  border-left: 3px solid var(--color-deep-tarn);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: var(--space-md) var(--space-lg);
  font-size: 15px;
  color: var(--color-stone);
  display: flex;
  align-items: flex-start;
  gap: var(--space-sm);
}

.callout__icon {
  flex-shrink: 0;
  width: 16px;
  height: 16px;
  margin-top: 2px;
  color: var(--color-stone);
}

/* --- Blog Index --- */
.blog-list {
  max-width: var(--content-width);
  margin: 0 auto;
}

.blog-item {
  padding: var(--space-xl) 0;
  border-bottom: 1px solid var(--color-divider);
}

.blog-item:first-child {
  padding-top: 0;
}

.blog-item:last-child {
  border-bottom: none;
}

.blog-item__tag {
  display: inline-block;
  background: var(--color-mist);
  color: var(--color-stone);
  font-size: 12px;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-sm);
}

.blog-item__title {
  font-size: var(--text-h3);
  font-weight: 600;
  color: var(--color-deep-tarn);
  margin-bottom: var(--space-sm);
  line-height: 1.3;
}

.blog-item__title a {
  color: inherit;
  text-decoration: none;
}

.blog-item__title a:hover {
  color: var(--color-current-day);
  text-decoration: none;
}

.blog-item__excerpt {
  font-size: 16px;
  color: var(--color-stone);
  line-height: 1.6;
  margin-bottom: var(--space-sm);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.blog-item__date {
  font-size: var(--text-small);
  color: var(--color-caption);
}

/* --- Blog Post / Article --- */
.article {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: var(--space-3xl) var(--space-lg);
}

.article__meta {
  margin-bottom: var(--space-lg);
}

.article__tag {
  display: inline-block;
  font-size: 12px;
  font-weight: 600;
  color: var(--color-stone);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-right: var(--space-md);
}

.article__date {
  font-size: var(--text-small);
  color: var(--color-caption);
}

.article__title {
  font-size: var(--text-h1);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.015em;
  color: var(--color-deep-tarn);
  margin-bottom: var(--space-2xl);
}

/* Article body prose */
.article__body h2 {
  margin-top: var(--space-2xl);
  margin-bottom: var(--space-md);
}

.article__body h3 {
  margin-top: var(--space-xl);
  margin-bottom: var(--space-sm);
}

.article__body p {
  margin-bottom: var(--space-lg);
}

.article__body ul,
.article__body ol {
  margin-bottom: var(--space-lg);
  padding-left: var(--space-lg);
}

.article__body ul {
  list-style: disc;
}

.article__body ol {
  list-style: decimal;
}

.article__body li {
  margin-bottom: var(--space-sm);
  line-height: 1.7;
}

.article__body a {
  text-decoration: underline;
  text-underline-offset: 2px;
}

.article__body blockquote {
  border-left: 3px solid var(--color-deep-tarn);
  padding-left: var(--space-md);
  margin: var(--space-xl) 0;
  font-style: italic;
  color: var(--color-stone);
}

.article__body code {
  font-family: var(--font-mono);
  font-size: var(--text-code-inline);
  background: var(--color-code-bg);
  padding: 2px 6px;
  border-radius: var(--radius-sm);
}

.article__body pre {
  background: var(--color-code-bg);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin: var(--space-xl) 0;
}

.article__body pre code {
  background: none;
  padding: 0;
  font-size: var(--text-code);
  line-height: 1.6;
}

.article__body strong {
  color: var(--color-deep-tarn);
}

.article__body .callout {
  margin: var(--space-xl) 0;
}

/* --- Footer --- */
.footer {
  background: var(--color-deep-tarn);
  color: var(--color-footer-text);
  padding: var(--space-3xl) 0 var(--space-xl);
}

.footer__inner {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--space-2xl);
  max-width: var(--page-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.footer__brand {
  font-size: 20px;
  font-weight: 700;
  color: var(--color-white);
  margin-bottom: var(--space-sm);
}

.footer__tagline {
  font-size: 16px;
  color: var(--color-footer-text);
}

.footer__heading {
  font-size: var(--text-small);
  font-weight: 600;
  color: var(--color-white);
  margin-bottom: var(--space-md);
  letter-spacing: 0.01em;
}

.footer__links {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer__link {
  color: var(--color-footer-text);
  font-size: var(--text-small);
  text-decoration: none;
  transition: color 150ms ease;
}

.footer__link:hover {
  color: var(--color-white);
  text-decoration: underline;
}

.footer__bottom {
  grid-column: 1 / -1;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding-top: var(--space-lg);
  margin-top: var(--space-lg);
  font-size: var(--text-small);
  color: var(--color-footer-text);
}

.footer__privacy-note {
  font-size: var(--text-small);
  margin-bottom: var(--space-sm);
}

/* --- Responsive: Tablet (640-1024) --- */
@media (max-width: 1024px) {
  :root {
    --text-hero: 40px;
    --text-h1: 32px;
    --text-h2: 24px;
  }

  .section {
    padding: var(--space-3xl) 0;
  }

  .hero {
    padding: var(--space-4xl) 0 var(--space-3xl);
  }

  .features {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-xl);
  }

  .steps {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
  }

  .footer__inner {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-xl);
  }
}

/* --- Responsive: Mobile (<640) --- */
@media (max-width: 640px) {
  :root {
    --text-hero: 32px;
    --text-h1: 28px;
    --text-h2: 22px;
    --text-body: 16px;
  }

  .container {
    padding: 0 var(--space-md);
  }

  .nav {
    height: 56px;
  }

  .nav__inner {
    padding: 0 var(--space-md);
  }

  .nav__links {
    display: none;
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background: var(--color-white);
    flex-direction: column;
    padding: var(--space-md);
    gap: 0;
    border-bottom: 1px solid var(--color-divider);
    box-shadow: var(--shadow-md);
  }

  .nav__links.open {
    display: flex;
  }

  .nav__link {
    padding: var(--space-md);
    width: 100%;
    display: block;
  }

  .nav__toggle {
    display: block;
  }

  .hero {
    padding: var(--space-3xl) 0 var(--space-2xl);
  }

  .hero__subtitle {
    font-size: 18px;
  }

  .hero__actions {
    flex-direction: column;
  }

  .hero__actions .btn {
    width: 100%;
    max-width: 280px;
  }

  .section {
    padding: var(--space-2xl) 0;
  }

  .section__header {
    margin-bottom: var(--space-xl);
  }

  .features {
    grid-template-columns: 1fr;
    gap: var(--space-xl);
  }

  .feature__header {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-bottom: var(--space-sm);
  }

  .feature__icon {
    margin-bottom: 0;
    flex-shrink: 0;
  }

  .feature__title {
    margin-bottom: 0;
  }

  .steps {
    grid-template-columns: 1fr;
    gap: var(--space-xl);
  }

  .comparison th,
  .comparison td {
    padding: var(--space-sm) var(--space-md);
    font-size: var(--text-small);
  }

  .footer__inner {
    grid-template-columns: 1fr;
    gap: var(--space-xl);
  }

  .article {
    padding: var(--space-xl) var(--space-md);
  }

  .article__title {
    font-size: var(--text-h1);
  }
}

/* --- Hamburger active state --- */
.nav__toggle[aria-expanded="true"] .nav__toggle-open {
  display: none;
}

.nav__toggle[aria-expanded="true"] .nav__toggle-close {
  display: block;
}

/* --- Reduced Motion --- */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition: none !important;
    animation: none !important;
  }
}

/* --- Print --- */
@media print {
  .nav,
  .footer,
  .hero__actions {
    display: none;
  }

  body {
    color: #000;
    background: #fff;
  }
}