:root {
  --color-bg: #ffffff;
  --color-bg-subtle: #f7f6f3;
  --color-bg-hover: rgba(57, 97, 130, 0.07);
  --color-text: var(--color-primary);
  --color-text-secondary: #5b6b78;
  --color-text-faint: #8994a0;
  --color-border: #e5e2dc;
  --color-primary: #396182;
  --color-primary-hover: #2b4e6a;
  --color-accent: #2f8f3d;
  --color-code-bg: #f1f0ec;
  --shadow-card: 0 1px 2px rgba(20, 24, 30, 0.04), 0 4px 14px rgba(20, 24, 30, 0.05);
  --shadow-dropdown: 0 12px 32px rgba(20, 24, 30, 0.16);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter", Roboto, Helvetica, Arial,
    sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

/* Automatic (system-driven) dark mode — applies when the user hasn't made an
   explicit choice via the toggle (see html[data-theme] overrides below). */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #16191d;
    --color-bg-subtle: #1c2126;
    --color-bg-hover: rgba(127, 168, 201, 0.1);
    --color-text: #e7e9ea;
    --color-text-secondary: #a3adb6;
    --color-text-faint: #6d7680;
    --color-border: #2b3036;
    --color-primary: #86b2d6;
    --color-primary-hover: #a9cae6;
    --color-accent: #5fd071;
    --color-code-bg: #1f242a;
    --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.3), 0 4px 14px rgba(0, 0, 0, 0.3);
    --shadow-dropdown: 0 12px 32px rgba(0, 0, 0, 0.5);
  }
}

/* Explicit choice from the theme toggle overrides system preference either way.
   Higher specificity than :root, so these win regardless of the media query above. */
html[data-theme="dark"] {
  --color-bg: #16191d;
  --color-bg-subtle: #1c2126;
  --color-bg-hover: rgba(127, 168, 201, 0.1);
  --color-text: #e7e9ea;
  --color-text-secondary: #a3adb6;
  --color-text-faint: #6d7680;
  --color-border: #2b3036;
  --color-primary: #86b2d6;
  --color-primary-hover: #a9cae6;
  --color-accent: #5fd071;
  --color-code-bg: #1f242a;
  --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.3), 0 4px 14px rgba(0, 0, 0, 0.3);
  --shadow-dropdown: 0 12px 32px rgba(0, 0, 0, 0.5);
}

html[data-theme="light"] {
  --color-bg: #ffffff;
  --color-bg-subtle: #f7f6f3;
  --color-bg-hover: rgba(57, 97, 130, 0.07);
  --color-text: var(--color-primary);
  --color-text-secondary: #5b6b78;
  --color-text-faint: #8994a0;
  --color-border: #e5e2dc;
  --color-primary: #396182;
  --color-primary-hover: #2b4e6a;
  --color-accent: #2f8f3d;
  --color-code-bg: #f1f0ec;
  --shadow-card: 0 1px 2px rgba(20, 24, 30, 0.04), 0 4px 14px rgba(20, 24, 30, 0.05);
  --shadow-dropdown: 0 12px 32px rgba(20, 24, 30, 0.16);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg-subtle);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-primary);
  text-decoration: none;
}

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

::selection {
  background: rgba(47, 143, 61, 0.22);
}

/* Header */

.site-header {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  background: var(--color-primary);
  border-bottom: 1px solid var(--color-border);
  padding: 0.7rem 1.5rem;
  position: sticky;
  top: 0;
  z-index: 20;
}

@media (prefers-color-scheme: dark) {
  .site-header {
    background: var(--color-bg);
  }
}

html[data-theme="dark"] .site-header {
  background: var(--color-bg);
}

html[data-theme="light"] .site-header {
  background: var(--color-primary);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  /* white works on both the dark-mode header (--color-bg is near-black)
     and the blue light-mode header, so it doesn't need to track --color-text. */
  color: #ffffff;
  font-weight: 600;
  font-size: 1rem;
  white-space: nowrap;
}

.brand:hover {
  color: #ffffff;
  text-decoration: none;
}

.brand-logo {
  height: 24px;
  width: auto;
  /* the source asset is TrackZero's "cream" mark, made for dark surfaces —
     force it to pure white for the (now blue) light header; dark mode shows
     it unfiltered below. */
  filter: brightness(0) invert(1);
}

@media (prefers-color-scheme: dark) {
  .brand-logo {
    filter: none;
  }
}

html[data-theme="dark"] .brand-logo {
  filter: none;
}

html[data-theme="light"] .brand-logo {
  filter: brightness(0) invert(1);
}

/* Theme toggle */

.theme-toggle {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: 7px;
  border: 1px solid var(--color-border);
  background: var(--color-bg-subtle);
  color: var(--color-text-secondary);
  cursor: pointer;
}

.theme-toggle:hover {
  color: var(--color-text);
  border-color: var(--color-primary);
}

.theme-toggle svg {
  width: 17px;
  height: 17px;
}

.theme-toggle .icon-sun {
  display: none;
}

.theme-toggle .icon-moon {
  display: block;
}

@media (prefers-color-scheme: dark) {
  .theme-toggle .icon-sun {
    display: block;
  }
  .theme-toggle .icon-moon {
    display: none;
  }
}

html[data-theme="dark"] .theme-toggle .icon-sun {
  display: block;
}

html[data-theme="dark"] .theme-toggle .icon-moon {
  display: none;
}

html[data-theme="light"] .theme-toggle .icon-sun {
  display: none;
}

html[data-theme="light"] .theme-toggle .icon-moon {
  display: block;
}

.search-wrap {
  position: relative;
  flex: 1;
  max-width: 420px;
  margin-left: auto;
  display: flex;
  align-items: center;
}

.search-icon {
  position: absolute;
  left: 0.7rem;
  width: 16px;
  height: 16px;
  color: var(--color-text-faint);
  pointer-events: none;
}

#search-input {
  width: 100%;
  padding: 0.45rem 2.1rem 0.45rem 2.15rem;
  border-radius: 7px;
  border: 1px solid var(--color-border);
  background: var(--color-bg-subtle);
  color: var(--color-text);
  font-size: 0.9rem;
  font-family: inherit;
}

#search-input::placeholder {
  color: var(--color-text-faint);
}

#search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-bg);
}

.search-kbd {
  position: absolute;
  right: 0.55rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-text-faint);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 0.05rem 0.4rem;
  pointer-events: none;
}

#search-input:focus ~ .search-kbd {
  display: none;
}

.search-results {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  right: 0;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  box-shadow: var(--shadow-dropdown);
  max-height: 380px;
  overflow-y: auto;
}

.search-result {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.6rem 0.9rem;
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text);
}

.search-result:last-child {
  border-bottom: none;
}

.search-result:hover {
  background: var(--color-bg-hover);
  text-decoration: none;
}

.sr-title {
  font-weight: 500;
  font-size: 0.92rem;
}

.sr-category {
  color: var(--color-text-secondary);
  font-size: 0.8rem;
  white-space: nowrap;
}

.search-empty {
  padding: 0.7rem 0.9rem;
  color: var(--color-text-secondary);
  font-size: 0.9rem;
}

/* Layout */

.layout {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr) 240px;
  max-width: 1360px;
  margin: 0 auto;
  align-items: start;
}

.layout--no-toc {
  grid-template-columns: 260px minmax(0, 1fr);
}

/* Sidebar */

.sidebar {
  padding: 1.5rem 1rem 3rem;
  position: sticky;
  top: 53px;
  max-height: calc(100vh - 53px);
  overflow-y: auto;
}

.sidebar-heading {
  margin: 1.3rem 0.55rem 0.45rem;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-faint);
}

.sidebar-heading:first-child {
  margin-top: 0.2rem;
}

.nav-group {
  margin-bottom: 0.15rem;
}

.nav-group summary {
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
  font-size: 0.92rem;
  padding: 0.45rem 0.55rem;
  border-radius: 6px;
  list-style: none;
  user-select: none;
}

.nav-group summary::-webkit-details-marker {
  display: none;
}

.nav-group summary::before {
  content: "";
  width: 0;
  height: 0;
  border-left: 4px solid var(--color-text-faint);
  border-top: 3px solid transparent;
  border-bottom: 3px solid transparent;
  transition: transform 0.15s ease;
  flex-shrink: 0;
}

.nav-group[open] summary::before {
  transform: rotate(90deg);
}

.nav-group summary:hover {
  background: var(--color-bg-hover);
}

.nav-icon {
  font-size: 0.95rem;
  line-height: 1;
  width: 1.1em;
  text-align: center;
  flex-shrink: 0;
}

.nav-group ul {
  list-style: none;
  margin: 0.1rem 0 0.5rem 0;
  padding: 0;
  position: relative;
}

.nav-group ul::before {
  content: "";
  position: absolute;
  top: 0.1rem;
  bottom: 0.4rem;
  left: 1.05rem;
  width: 1px;
  background: var(--color-border);
}

.nav-group li a {
  display: block;
  padding: 0.35rem 0.6rem 0.35rem 1.9rem;
  border-radius: 6px;
  color: var(--color-text-secondary);
  font-size: 0.88rem;
  line-height: 1.4;
  position: relative;
}

.nav-group li a:hover {
  background: var(--color-bg-hover);
  color: var(--color-text);
  text-decoration: none;
}

.nav-group li a.active {
  color: var(--color-primary);
  font-weight: 700;
}

.nav-group li a.active::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 1.05rem;
  width: 2px;
  background: var(--color-primary);
}

/* Content */

.content {
  padding: 2.5rem 3rem 4rem;
  min-width: 0;
}

.content article {
  max-width: 68ch;
}

.content p a,
.content li a,
.content td a,
.content blockquote a {
  text-decoration: underline;
}

.guide-next {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin: 3rem 0 0;
  padding: 1.1rem 1.4rem;
  max-width: 68ch;
  border: 1px solid var(--color-border);
  border-radius: 10px;
  text-decoration: none !important;
  color: var(--color-text);
  transition: border-color 0.15s ease;
}

.guide-next:hover {
  border-color: var(--color-primary);
}

.guide-next-label {
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--color-text-secondary);
  flex-shrink: 0;
}

.guide-next-title {
  flex: 1;
  font-weight: 600;
  color: var(--color-primary);
}

.guide-next i {
  color: var(--color-primary);
  flex-shrink: 0;
}

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-size: 0.76rem;
  font-weight: 700;
  color: var(--color-text-secondary);
  margin: 0 0 0.6rem;
}

.content h1 {
  color: var(--color-text);
  font-size: 2rem;
  line-height: 1.25;
  margin: 0 0 1.4rem;
  letter-spacing: -0.01em;
}

.content h2 {
  font-size: 1.4rem;
  color: var(--color-text);
  margin: 2.4rem 0 1rem;
  letter-spacing: -0.01em;
  scroll-margin-top: 70px;
}

.content h3 {
  font-size: 1.12rem;
  color: var(--color-text);
  margin: 1.8rem 0 0.8rem;
  scroll-margin-top: 70px;
}

.content p {
  margin: 0 0 1.1rem;
  color: var(--color-text);
}

.content ul,
.content ol {
  margin: 0 0 1.1rem;
  padding-left: 1.4rem;
}

.content li {
  margin-bottom: 0.4rem;
}

.content li > ul,
.content li > ol {
  margin-top: 0.4rem;
  margin-bottom: 0.2rem;
}

.content strong {
  font-weight: 600;
}

.content img,
.content video {
  max-width: 100%;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-card);
  margin: 0.5rem 0 1.4rem;
  display: block;
}

.video-embed {
  position: relative;
  aspect-ratio: 16 / 9;
  max-width: 100%;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-card);
  margin: 0.5rem 0 1.4rem;
  overflow: hidden;
}

.video-embed iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.content code {
  font-family: var(--font-mono);
  background: var(--color-code-bg);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.87em;
}

.content blockquote {
  margin: 0 0 1.1rem;
  padding: 0.2rem 1rem;
  border-left: 3px solid var(--color-border);
  color: var(--color-text-secondary);
}

.content hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 2.4rem 0;
}

.content table {
  border-collapse: collapse;
  width: 100%;
  margin: 0 0 1.4rem;
  font-size: 0.92rem;
}

.content th,
.content td {
  border: 1px solid var(--color-border);
  padding: 0.5rem 0.7rem;
  text-align: left;
}

.content th {
  background: var(--color-bg-subtle);
  font-weight: 600;
}

.lede {
  font-size: 1.15rem;
  color: var(--color-text-secondary);
  max-width: 640px;
}

/* Table of contents */

.toc {
  padding: 2.5rem 1.5rem 3rem 0;
  position: sticky;
  top: 53px;
  max-height: calc(100vh - 53px);
  overflow-y: auto;
  font-size: 0.86rem;
}

.toc-title {
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.74rem;
  color: var(--color-text-faint);
  margin: 0 0 0.6rem;
}

.toc ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.toc li > ul {
  padding-left: 0.9rem;
}

.toc a {
  display: block;
  padding: 0.28rem 0;
  color: var(--color-text-secondary);
  border-left: 2px solid transparent;
  padding-left: 0.7rem;
  margin-left: -0.7rem;
}

.toc a:hover {
  color: var(--color-primary);
  text-decoration: none;
  border-left-color: var(--color-border);
}

/* Homepage */

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 1rem;
  margin-top: 1.75rem;
}

.category-card {
  display: block;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  padding: 1.2rem 1.3rem;
  color: var(--color-text);
  box-shadow: var(--shadow-card);
  text-decoration: none;
  transition: transform 0.12s ease, border-color 0.12s ease;
}

.category-card:hover {
  border-color: var(--color-primary);
  text-decoration: none;
  transform: translateY(-2px);
}

.category-card-icon {
  font-size: 1.5rem;
  display: block;
  margin-bottom: 0.5rem;
  color: var(--color-primary);
}

.category-card h3 {
  margin: 0 0 0.3rem 0;
  font-size: 1.02rem;
  color: var(--color-text);
}

.category-card p {
  margin: 0;
  color: var(--color-text-secondary);
  font-size: 0.86rem;
}

@media (max-width: 1100px) {
  .layout {
    grid-template-columns: 240px minmax(0, 1fr);
  }

  .toc {
    display: none;
  }
}

@media (max-width: 800px) {
  .layout,
  .layout--no-toc {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    max-height: none;
    border-bottom: 1px solid var(--color-border);
  }

  .content {
    padding: 1.75rem 1.25rem 3rem;
  }

  .search-wrap {
    max-width: none;
  }
}