/* =============================================
   tcaoanhvo — Main Stylesheet
   Apple-inspired clean documentation design
   ============================================= */

@import url('https://fonts.googleapis.com/css2?family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;1,9..40,400&family=JetBrains+Mono:wght@400;500;600&display=swap');

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

:root {
  --white:       #ffffff;
  --gray-50:     #f5f5f7;
  --gray-100:    #e8e8ed;
  --gray-200:    #d2d2d7;
  --gray-400:    #86868b;
  --gray-600:    #515154;
  --gray-900:    #1d1d1f;
  --black:       #000000;

  --blue:        #0071e3;
  --blue-hover:  #0077ed;
  --blue-light:  #e8f0fb;
  --green:       #1d9e1d;
  --green-light: #e6f6e6;
  --orange:      #d4580a;
  --orange-light:#fef3e8;
  --red:         #c0392b;

  --font-sans:   'DM Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono:   'JetBrains Mono', 'SF Mono', Menlo, monospace;

  --nav-h:       60px;
  --sidebar-w:   260px;
  --content-max: 840px;
  --radius:      12px;
  --radius-sm:   8px;

  --shadow-sm:   0 1px 3px rgba(0,0,0,.08);
  --shadow-md:   0 4px 16px rgba(0,0,0,.10);
  --shadow-lg:   0 12px 40px rgba(0,0,0,.12);
  --transition:  all .2s ease;
}

html { scroll-behavior: smooth; font-size: 16px; }

body {
  font-family: var(--font-sans);
  color: var(--gray-900);
  background: var(--white);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--blue); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--blue-hover); }

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

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--gray-200); border-radius: 99px; }

/* ── Top Navigation ── */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-h);
  background: rgba(255,255,255,.85);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--gray-100);
  z-index: 1000;
  display: flex;
  align-items: center;
  padding: 0 24px;
  gap: 0;
}

.nav__logo {
  font-size: 18px;
  font-weight: 600;
  color: var(--gray-900);
  letter-spacing: -.3px;
  white-space: nowrap;
}
.nav__logo span { color: var(--blue); }

.nav__links {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: 32px;
  list-style: none;
}
.nav__links a {
  color: var(--gray-600);
  font-size: 14px;
  font-weight: 400;
  padding: 6px 12px;
  border-radius: 8px;
}
.nav__links a:hover,
.nav__links a.active {
  color: var(--gray-900);
  background: var(--gray-50);
}

.nav__spacer { flex: 1; }

.nav__search {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--gray-50);
  border: 1px solid var(--gray-100);
  border-radius: 10px;
  padding: 7px 14px;
  cursor: pointer;
  transition: var(--transition);
}
.nav__search:hover { background: var(--gray-100); }
.nav__search input {
  border: none;
  background: transparent;
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--gray-900);
  outline: none;
  width: 180px;
}
.nav__search input::placeholder { color: var(--gray-400); }
.nav__search-icon { color: var(--gray-400); font-size: 14px; }

/* ── Page Layout ── */
.page-wrapper {
  display: flex;
  padding-top: var(--nav-h);
  min-height: 100vh;
}

/* ── Sidebar ── */
.sidebar {
  position: fixed;
  top: var(--nav-h);
  left: 0;
  width: var(--sidebar-w);
  height: calc(100vh - var(--nav-h));
  overflow-y: auto;
  padding: 24px 0 48px;
  border-right: 1px solid var(--gray-100);
  background: var(--white);
}

.sidebar__section { margin-bottom: 28px; padding: 0 16px; }

.sidebar__label {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--gray-400);
  padding: 0 8px;
  margin-bottom: 6px;
}

.sidebar__menu { list-style: none; }
.sidebar__menu li a {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--gray-600);
  font-size: 14px;
  padding: 7px 8px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}
.sidebar__menu li a:hover {
  color: var(--gray-900);
  background: var(--gray-50);
}
.sidebar__menu li a.active {
  color: var(--blue);
  background: var(--blue-light);
  font-weight: 500;
}
.sidebar__menu li a .tag {
  margin-left: auto;
  font-size: 10px;
  font-weight: 600;
  padding: 2px 6px;
  border-radius: 99px;
  background: var(--green-light);
  color: var(--green);
}
.sidebar__menu li a .tag.easy { background: var(--green-light); color: var(--green); }
.sidebar__menu li a .tag.medium { background: var(--orange-light); color: var(--orange); }
.sidebar__menu li a .tag.hard { background: #fde8e8; color: var(--red); }

/* ── Main Content ── */
.main-content {
  margin-left: var(--sidebar-w);
  flex: 1;
  padding: 48px 60px;
  max-width: calc(var(--sidebar-w) + var(--content-max) + 120px);
}

/* ── Article Typography ── */
.article__header { margin-bottom: 40px; padding-bottom: 32px; border-bottom: 1px solid var(--gray-100); }

.article__category {
  font-size: 13px;
  font-weight: 500;
  color: var(--blue);
  letter-spacing: .02em;
  margin-bottom: 10px;
  text-transform: uppercase;
}

.article__title {
  font-size: 36px;
  font-weight: 600;
  color: var(--gray-900);
  line-height: 1.15;
  letter-spacing: -.5px;
  margin-bottom: 12px;
}

.article__subtitle {
  font-size: 18px;
  font-weight: 300;
  color: var(--gray-600);
  line-height: 1.5;
  max-width: 600px;
}

.article__meta {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-top: 20px;
  font-size: 13px;
  color: var(--gray-400);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 99px;
  font-size: 12px;
  font-weight: 500;
}
.badge--easy   { background: var(--green-light); color: var(--green); }
.badge--medium { background: var(--orange-light); color: var(--orange); }
.badge--hard   { background: #fde8e8; color: var(--red); }
.badge--info   { background: var(--blue-light); color: var(--blue); }

/* ── Section Headings ── */
.article h2 {
  font-size: 22px;
  font-weight: 600;
  color: var(--gray-900);
  letter-spacing: -.2px;
  margin: 40px 0 14px;
}
.article h3 {
  font-size: 17px;
  font-weight: 600;
  color: var(--gray-900);
  margin: 28px 0 10px;
}
.article p {
  font-size: 15.5px;
  line-height: 1.75;
  color: var(--gray-600);
  margin-bottom: 16px;
}
.article p strong { color: var(--gray-900); font-weight: 500; }
.article ul, .article ol {
  padding-left: 22px;
  margin-bottom: 16px;
}
.article li {
  font-size: 15.5px;
  color: var(--gray-600);
  line-height: 1.75;
  margin-bottom: 4px;
}

/* ── Inline Code ── */
.article code:not(.hljs) {
  font-family: var(--font-mono);
  font-size: 13.5px;
  background: var(--gray-50);
  color: var(--blue);
  padding: 2px 6px;
  border-radius: 5px;
  border: 1px solid var(--gray-100);
}

/* ── Code Block ── */
.code-block {
  margin: 24px 0;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--gray-100);
  box-shadow: var(--shadow-sm);
}

.code-block__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 18px;
  background: var(--gray-50);
  border-bottom: 1px solid var(--gray-100);
}

.code-block__title {
  font-size: 13px;
  font-weight: 500;
  color: var(--gray-600);
  display: flex;
  align-items: center;
  gap: 8px;
}

.code-block__dots { display: flex; gap: 5px; }
.code-block__dot {
  width: 11px; height: 11px;
  border-radius: 50%;
}
.code-block__dot:nth-child(1) { background: #ff5f57; }
.code-block__dot:nth-child(2) { background: #ffbd2e; }
.code-block__dot:nth-child(3) { background: #28c840; }

.copy-btn {
  display: flex;
  align-items: center;
  gap: 5px;
  background: none;
  border: 1px solid var(--gray-200);
  border-radius: 6px;
  padding: 4px 10px;
  font-size: 12px;
  font-family: var(--font-sans);
  color: var(--gray-600);
  cursor: pointer;
  transition: var(--transition);
}
.copy-btn:hover { background: var(--white); color: var(--gray-900); }
.copy-btn.copied { color: var(--green); border-color: var(--green); }

.code-block pre {
  margin: 0;
  padding: 20px 22px;
  background: #fafafa;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 13.5px;
  line-height: 1.7;
}

/* ── Syntax Highlighting ── */
.tok-kw    { color: #c0392b; font-weight: 500; }
.tok-type  { color: #8e44ad; }
.tok-fn    { color: #2471a3; }
.tok-str   { color: #196f3d; }
.tok-num   { color: #d4580a; }
.tok-cmt   { color: #95a5a6; font-style: italic; }
.tok-pp    { color: #7d6608; }
.tok-op    { color: var(--gray-600); }

/* ── Callout boxes ── */
.callout {
  display: flex;
  gap: 14px;
  padding: 16px 18px;
  border-radius: var(--radius-sm);
  margin: 24px 0;
  font-size: 14.5px;
  line-height: 1.65;
}
.callout__icon { font-size: 18px; flex-shrink: 0; margin-top: 1px; }
.callout__body { color: var(--gray-600); }
.callout__body strong { color: var(--gray-900); }
.callout--info    { background: var(--blue-light); }
.callout--tip     { background: var(--green-light); }
.callout--warning { background: var(--orange-light); }

/* ── Complexity Table ── */
.complexity-table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14px;
}
.complexity-table th, .complexity-table td {
  text-align: left;
  padding: 10px 14px;
  border-bottom: 1px solid var(--gray-100);
}
.complexity-table th {
  font-size: 12px;
  font-weight: 600;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--gray-400);
  background: var(--gray-50);
}
.complexity-table tbody tr:hover { background: var(--gray-50); }
.complexity-table td:first-child { color: var(--gray-900); font-weight: 500; }
.complexity-table .good  { color: var(--green); font-weight: 500; }
.complexity-table .okay  { color: var(--orange); font-weight: 500; }
.complexity-table .bad   { color: var(--red); font-weight: 500; }

/* ── Interactive Demo ── */
.demo-section {
  background: var(--gray-50);
  border: 1px solid var(--gray-100);
  border-radius: var(--radius);
  padding: 28px;
  margin: 28px 0;
}
.demo-section h3 {
  font-size: 15px;
  font-weight: 600;
  color: var(--gray-900);
  margin: 0 0 18px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.demo-input-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.demo-label {
  font-size: 13px;
  color: var(--gray-600);
  font-weight: 500;
  min-width: 80px;
}
.demo-input {
  font-family: var(--font-mono);
  font-size: 14px;
  padding: 9px 14px;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-sm);
  background: var(--white);
  color: var(--gray-900);
  outline: none;
  flex: 1;
  min-width: 200px;
  transition: var(--transition);
}
.demo-input:focus { border-color: var(--blue); box-shadow: 0 0 0 3px rgba(0,113,227,.12); }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 9px 18px;
  border-radius: var(--radius-sm);
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  border: none;
}
.btn--primary {
  background: var(--blue);
  color: var(--white);
}
.btn--primary:hover { background: var(--blue-hover); transform: translateY(-1px); box-shadow: 0 4px 12px rgba(0,113,227,.3); }
.btn--primary:active { transform: translateY(0); }

.btn--ghost {
  background: var(--white);
  color: var(--gray-600);
  border: 1px solid var(--gray-200);
}
.btn--ghost:hover { background: var(--gray-50); color: var(--gray-900); }

.demo-output {
  margin-top: 16px;
  padding: 14px 18px;
  background: var(--white);
  border: 1px solid var(--gray-100);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--gray-600);
  min-height: 60px;
}
.demo-output .result-line { display: flex; align-items: flex-start; gap: 10px; }
.demo-output .result-label { color: var(--gray-400); min-width: 90px; font-size: 12px; margin-top: 2px; }
.demo-output .result-val { color: var(--gray-900); font-weight: 500; }
.demo-output .result-val.highlight { color: var(--blue); }

/* ── Visualizer ── */
.visualizer {
  display: flex;
  align-items: flex-end;
  gap: 5px;
  height: 100px;
  padding: 12px 0;
}
.vis-bar {
  flex: 1;
  border-radius: 4px 4px 0 0;
  background: var(--gray-200);
  position: relative;
  transition: all .3s ease;
  min-width: 20px;
}
.vis-bar.active   { background: var(--blue); }
.vis-bar.found    { background: var(--green); }
.vis-bar.compared { background: var(--orange-light); }
.vis-bar span {
  position: absolute;
  bottom: -20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 11px;
  color: var(--gray-400);
  font-family: var(--font-mono);
}

/* ── Home Page ── */
.hero {
  padding: 80px 0 60px;
  border-bottom: 1px solid var(--gray-100);
  margin-bottom: 56px;
}
.hero__eyebrow {
  font-size: 13px;
  font-weight: 500;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--blue);
  margin-bottom: 16px;
}
.hero__title {
  font-size: clamp(36px, 5vw, 56px);
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -.8px;
  color: var(--gray-900);
  margin-bottom: 20px;
  max-width: 700px;
}
.hero__title em {
  font-style: normal;
  color: var(--blue);
}
.hero__desc {
  font-size: 18px;
  font-weight: 300;
  color: var(--gray-600);
  line-height: 1.6;
  max-width: 560px;
  margin-bottom: 32px;
}
.hero__actions { display: flex; gap: 12px; flex-wrap: wrap; }

.btn--large { padding: 13px 26px; font-size: 15px; border-radius: 10px; }

/* Card Grid */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 16px;
  margin: 28px 0;
}

.card {
  background: var(--white);
  border: 1px solid var(--gray-100);
  border-radius: var(--radius);
  padding: 22px;
  transition: var(--transition);
  cursor: pointer;
  position: relative;
  overflow: hidden;
}
.card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--blue);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .25s ease;
}
.card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); }
.card:hover::before { transform: scaleX(1); }

.card__icon {
  font-size: 24px;
  margin-bottom: 12px;
}
.card__title {
  font-size: 15px;
  font-weight: 600;
  color: var(--gray-900);
  margin-bottom: 6px;
}
.card__desc {
  font-size: 13px;
  color: var(--gray-400);
  line-height: 1.5;
}
.card__meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--gray-100);
  font-size: 12px;
  color: var(--gray-400);
}

/* ── Section divider heading ── */
.section-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}
.section-heading h2 {
  font-size: 22px;
  font-weight: 600;
  color: var(--gray-900);
  letter-spacing: -.2px;
}
.section-heading a {
  font-size: 14px;
  color: var(--blue);
}

/* ── Breadcrumb ── */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--gray-400);
  margin-bottom: 24px;
}
.breadcrumb a { color: var(--gray-400); }
.breadcrumb a:hover { color: var(--blue); }
.breadcrumb__sep { color: var(--gray-200); }

/* ── Page navigation ── */
.page-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 56px;
  padding-top: 32px;
  border-top: 1px solid var(--gray-100);
}
.page-nav__btn {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 16px 20px;
  background: var(--white);
  border: 1px solid var(--gray-100);
  border-radius: var(--radius);
  transition: var(--transition);
  flex: 1;
  max-width: 220px;
  cursor: pointer;
}
.page-nav__btn:hover { box-shadow: var(--shadow-sm); transform: translateY(-1px); }
.page-nav__btn--next { text-align: right; margin-left: auto; }
.page-nav__dir { font-size: 12px; color: var(--gray-400); }
.page-nav__name { font-size: 14px; font-weight: 500; color: var(--blue); }

/* ── Footer ── */
.footer {
  margin-left: var(--sidebar-w);
  border-top: 1px solid var(--gray-100);
  padding: 32px 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 13px;
  color: var(--gray-400);
}
.footer a { color: var(--gray-400); }
.footer a:hover { color: var(--blue); }

/* ── Responsive ── */
@media (max-width: 900px) {
  .sidebar { display: none; }
  .main-content, .footer { margin-left: 0; padding: 32px 24px; }
}

@media (max-width: 600px) {
  .nav__links { display: none; }
  .nav__search input { width: 120px; }
  .hero__title { font-size: 32px; }
  .article__title { font-size: 26px; }
}

/* ── Animations ── */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}
.fade-up { animation: fadeUp .5s ease forwards; }
.fade-up:nth-child(1) { animation-delay: .05s; }
.fade-up:nth-child(2) { animation-delay: .10s; }
.fade-up:nth-child(3) { animation-delay: .15s; }
.fade-up:nth-child(4) { animation-delay: .20s; }
.fade-up:nth-child(5) { animation-delay: .25s; }
.fade-up:nth-child(6) { animation-delay: .30s; }

/* ── Sorting Visualizer (shared across all sorting pages) ── */
.sort-vis-wrap {
  background: var(--white);
  border: 1px solid var(--gray-100);
  border-radius: var(--radius);
  padding: 24px 24px 8px;
  margin: 20px 0;
}

.sort-bars {
  display: flex;
  align-items: flex-end;
  gap: 5px;
  height: 140px;
  padding-bottom: 24px;
  position: relative;
}

.sort-bar-col {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
  gap: 4px;
  min-width: 18px;
  max-width: 52px;
}

.sort-bar {
  width: 100%;
  border-radius: 5px 5px 0 0;
  transition: height .28s ease, background .22s ease, transform .22s ease;
  position: relative;
}

.sort-bar.default   { background: #c7d2fe; }
.sort-bar.comparing { background: #fb923c; box-shadow: 0 0 0 2px #fb923c40; }
.sort-bar.swapping  { background: #f87171; box-shadow: 0 0 0 2px #f8717140; transform: scaleX(1.06); }
.sort-bar.pivot     { background: #a855f7; box-shadow: 0 0 0 2px #a855f740; }
.sort-bar.sorted    { background: #4ade80; }
.sort-bar.current   { background: #38bdf8; box-shadow: 0 0 0 2px #38bdf840; }
.sort-bar.min-mark  { background: #facc15; box-shadow: 0 0 0 2px #facc1540; }
.sort-bar.heap-root { background: #f472b6; box-shadow: 0 0 0 2px #f472b640; }

.sort-bar-val {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--gray-400);
  line-height: 1;
  white-space: nowrap;
}

.sort-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.sort-speed {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--gray-600);
}
.sort-speed input[type=range] {
  width: 80px;
  accent-color: var(--blue);
}

.sort-stats {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  padding: 12px 16px;
  background: var(--gray-50);
  border-radius: var(--radius-sm);
  margin: 12px 0 0;
}

.sort-stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.sort-stat__label {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--gray-400);
}

.sort-stat__val {
  font-size: 22px;
  font-weight: 600;
  color: var(--gray-900);
  font-family: var(--font-mono);
}

.sort-stat__val.blue   { color: var(--blue); }
.sort-stat__val.orange { color: var(--orange); }
.sort-stat__val.green  { color: var(--green); }

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  font-size: 12px;
  color: var(--gray-600);
  margin: 4px 0 12px;
}
.legend-item {
  display: flex;
  align-items: center;
  gap: 5px;
}
.legend-dot {
  width: 12px; height: 12px;
  border-radius: 3px;
  flex-shrink: 0;
}

/* Phase log */
.phase-log {
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.9;
  color: var(--gray-600);
  height: 100px;
  overflow-y: auto;
  padding: 10px 14px;
  background: var(--white);
  border: 1px solid var(--gray-100);
  border-radius: var(--radius-sm);
  margin-top: 12px;
}
.phase-log .log-swap    { color: #ef4444; }
.phase-log .log-compare { color: var(--orange); }
.phase-log .log-sorted  { color: var(--green); font-weight: 600; }
.phase-log .log-pivot   { color: #a855f7; font-weight: 600; }
.phase-log .log-pass    { color: var(--blue); font-weight: 600; }