/* =========================================================
   DSA Codex — shared stylesheet
   Aesthetic: editorial / typeset textbook
   ========================================================= */

@import url('https://fonts.googleapis.com/css2?family=Fraunces:opsz,wght@9..144,400;9..144,500;9..144,700;9..144,900&family=Newsreader:ital,wght@0,400;0,500;0,600;1,400&family=JetBrains+Mono:wght@400;500;700&display=swap');

:root {
  --paper: #f5efe4;
  --paper-deep: #ece4d4;
  --ink: #1a1612;
  --ink-soft: #3d342a;
  --rule: #2a221a;
  --accent: #b8341f;        /* deep vermilion */
  --accent-soft: #d97757;
  --gold: #a07b2c;
  --leaf: #4a6741;
  --shadow: rgba(26, 22, 18, 0.08);
  --code-bg: #1e1a16;
  --code-text: #e8dfd0;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  background: var(--paper);
  background-image:
    radial-gradient(at 15% 10%, rgba(184, 52, 31, 0.04) 0px, transparent 50%),
    radial-gradient(at 85% 90%, rgba(160, 123, 44, 0.05) 0px, transparent 50%);
  color: var(--ink);
  font-family: 'Newsreader', Georgia, serif;
  font-size: 18px;
  line-height: 1.65;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

/* paper grain overlay */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.35;
  z-index: 1;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2'/%3E%3CfeColorMatrix values='0 0 0 0 0.1 0 0 0 0 0.08 0 0 0 0 0.06 0 0 0 0.08 0'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* ============== NAV ============== */
nav.topbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--paper);
  border-bottom: 1px solid var(--rule);
  padding: 0.9rem 2.5rem;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  backdrop-filter: blur(8px);
}

.brand {
  font-family: 'Fraunces', serif;
  font-weight: 900;
  font-size: 1.4rem;
  letter-spacing: -0.02em;
  color: var(--ink);
  text-decoration: none;
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
}
.brand::before {
  content: '§';
  color: var(--accent);
  font-style: italic;
  font-weight: 400;
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}
.nav-links a {
  font-family: 'Fraunces', serif;
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--ink-soft);
  text-decoration: none;
  position: relative;
  padding-bottom: 2px;
  transition: color 0.2s;
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
}
.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--accent);
}

/* ============== HERO ============== */
.hero {
  padding: 5rem 2.5rem 4rem;
  max-width: 1400px;
  margin: 0 auto;
  position: relative;
  z-index: 2;
}
.hero-eyebrow {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.8rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 1.5rem;
}
.hero h1 {
  font-family: 'Fraunces', serif;
  font-weight: 900;
  font-size: clamp(3rem, 8vw, 6.5rem);
  line-height: 0.95;
  letter-spacing: -0.04em;
  margin-bottom: 2rem;
  font-variation-settings: 'opsz' 144;
}
.hero h1 em {
  font-style: italic;
  font-weight: 400;
  color: var(--accent);
}
.hero-sub {
  font-size: 1.3rem;
  max-width: 720px;
  color: var(--ink-soft);
  line-height: 1.5;
}

/* ============== LAYOUT WITH SIDEBAR ============== */
.layout {
  max-width: 1400px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 4rem;
  padding: 3rem 2.5rem 6rem;
  position: relative;
  z-index: 2;
}

aside.toc {
  position: sticky;
  top: 5rem;
  align-self: start;
  max-height: calc(100vh - 7rem);
  overflow-y: auto;
  padding-right: 1rem;
  border-right: 1px solid var(--rule);
}
.toc-title {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.7rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink-soft);
  margin-bottom: 1rem;
}
.toc ol {
  list-style: none;
  counter-reset: toc;
}
.toc ol li {
  counter-increment: toc;
  margin-bottom: 0.4rem;
  font-size: 0.92rem;
}
.toc ol li a {
  color: var(--ink-soft);
  text-decoration: none;
  display: flex;
  gap: 0.6rem;
  padding: 0.25rem 0;
  border-bottom: 1px dotted transparent;
  transition: all 0.2s;
}
.toc ol li a::before {
  content: counter(toc, decimal-leading-zero);
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  color: var(--gold);
  flex-shrink: 0;
}
.toc ol li a:hover {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

/* ============== ARTICLE ============== */
article.content {
  max-width: 780px;
}

section.topic {
  margin-bottom: 5rem;
  scroll-margin-top: 5rem;
}

.section-number {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.8rem;
  letter-spacing: 0.15em;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

h2.topic-title {
  font-family: 'Fraunces', serif;
  font-weight: 700;
  font-size: clamp(2rem, 4vw, 3rem);
  line-height: 1.05;
  letter-spacing: -0.03em;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 2px solid var(--rule);
}

h3.subhead {
  font-family: 'Fraunces', serif;
  font-weight: 600;
  font-style: italic;
  font-size: 1.5rem;
  margin: 2.5rem 0 1rem;
  color: var(--ink);
}

h4.minor {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.8rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 1.5rem 0 0.5rem;
}

article.content p {
  margin-bottom: 1.2rem;
  hyphens: auto;
}

article.content p:first-of-type::first-letter,
.dropcap::first-letter {
  font-family: 'Fraunces', serif;
  font-weight: 900;
  font-size: 4.5rem;
  float: left;
  line-height: 0.85;
  margin: 0.1rem 0.6rem -0.2rem 0;
  color: var(--accent);
}

.analogy {
  background: var(--paper-deep);
  border-left: 3px solid var(--accent);
  padding: 1.2rem 1.5rem;
  margin: 1.5rem 0;
  font-style: italic;
  font-size: 1.05rem;
  position: relative;
}
.analogy::before {
  content: 'Analogy';
  position: absolute;
  top: -10px;
  left: 1rem;
  background: var(--paper);
  padding: 0 0.6rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.7rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  font-style: normal;
}

.callout {
  background: var(--paper-deep);
  border: 1px solid var(--rule);
  padding: 1.2rem 1.5rem;
  margin: 1.5rem 0;
  border-radius: 2px;
}
.callout-title {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--gold);
  margin-bottom: 0.5rem;
}

ul.list, ol.list {
  margin: 1rem 0 1.2rem 1.5rem;
}
ul.list li, ol.list li {
  margin-bottom: 0.5rem;
}

/* ============== CODE ============== */
.code-block {
  background: var(--code-bg);
  color: var(--code-text);
  padding: 1.5rem 1.8rem;
  margin: 1.5rem 0;
  border-radius: 4px;
  overflow-x: auto;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.85rem;
  line-height: 1.6;
  box-shadow: 0 8px 30px var(--shadow);
  position: relative;
}
.code-block::before {
  content: attr(data-lang);
  position: absolute;
  top: 0.5rem;
  right: 0.9rem;
  font-size: 0.65rem;
  letter-spacing: 0.15em;
  color: rgba(232, 223, 208, 0.4);
  text-transform: uppercase;
}
.code-block pre { margin: 0; }
.code-block code { font-family: inherit; }

/* Java syntax colors */
.tok-kw  { color: #e8a87c; }       /* keywords: public, class, if */
.tok-typ { color: #c8a0e0; }       /* types: int, String, List */
.tok-str { color: #a8c8a0; }       /* strings */
.tok-num { color: #f0b878; }       /* numbers */
.tok-com { color: #6a6258; font-style: italic; }  /* comments */
.tok-fn  { color: #e8d088; }       /* function names */

code.inline {
  font-family: 'JetBrains Mono', monospace;
  background: var(--paper-deep);
  border: 1px solid var(--rule);
  padding: 0.1rem 0.4rem;
  border-radius: 3px;
  font-size: 0.85em;
  color: var(--ink);
}

/* ============== TABLES ============== */
table.complexity {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.95rem;
}
table.complexity th,
table.complexity td {
  padding: 0.7rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--rule);
}
table.complexity th {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  border-bottom: 2px solid var(--rule);
}
table.complexity tr:hover td { background: var(--paper-deep); }
table.complexity td code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.85em;
}

/* complexity badges */
.bigO {
  display: inline-block;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.78rem;
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
  font-weight: 500;
}
.bigO.good { background: rgba(74, 103, 65, 0.18); color: #2f4426; }
.bigO.ok   { background: rgba(160, 123, 44, 0.18); color: #6b5018; }
.bigO.bad  { background: rgba(184, 52, 31, 0.18); color: var(--accent); }

/* ============== LEETCODE CARDS ============== */
.problems {
  margin: 2rem 0 1rem;
}
.problems-title {
  font-family: 'Fraunces', serif;
  font-weight: 600;
  font-size: 1.3rem;
  margin-bottom: 1rem;
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
}
.problems-title::before {
  content: '';
  width: 22px;
  height: 1px;
  background: var(--accent);
}
.problem-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 0.8rem;
}
.problem-card {
  background: var(--paper-deep);
  border: 1px solid var(--rule);
  padding: 0.9rem 1.1rem;
  text-decoration: none;
  color: var(--ink);
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  transition: all 0.2s;
  border-radius: 3px;
  position: relative;
}
.problem-card:hover {
  background: var(--ink);
  color: var(--paper);
  transform: translateY(-2px);
  box-shadow: 0 8px 20px var(--shadow);
}
.problem-card:hover .pc-num,
.problem-card:hover .pc-diff {
  color: var(--paper-deep);
}
.pc-num {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.7rem;
  color: var(--gold);
  letter-spacing: 0.05em;
}
.pc-title {
  font-family: 'Fraunces', serif;
  font-size: 1.05rem;
  font-weight: 500;
  line-height: 1.2;
}
.pc-diff {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-top: 0.2rem;
}
.pc-diff.easy   { color: var(--leaf); }
.pc-diff.medium { color: var(--gold); }
.pc-diff.hard   { color: var(--accent); }

/* ============== HOMEPAGE CARDS ============== */
.path-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 2.5rem 6rem;
  position: relative;
  z-index: 2;
}
.path-card {
  background: var(--paper-deep);
  border: 1px solid var(--rule);
  padding: 2rem 1.8rem;
  text-decoration: none;
  color: var(--ink);
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  position: relative;
  transition: all 0.3s;
  min-height: 280px;
}
.path-card::before {
  content: attr(data-num);
  position: absolute;
  top: 1rem;
  right: 1.3rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.7rem;
  color: var(--gold);
  letter-spacing: 0.15em;
}
.path-card:hover {
  background: var(--ink);
  color: var(--paper);
  transform: translateY(-4px);
  box-shadow: 0 12px 40px var(--shadow);
}
.path-card:hover .path-cta { color: var(--accent-soft); }
.path-card h3 {
  font-family: 'Fraunces', serif;
  font-weight: 700;
  font-size: 2rem;
  line-height: 1;
  letter-spacing: -0.02em;
  margin-top: 1.5rem;
}
.path-card p {
  font-size: 0.98rem;
  flex-grow: 1;
}
.path-cta {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.78rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin-top: auto;
  transition: color 0.2s;
}
.path-cta::after {
  content: ' →';
}

/* ============== INTRO BIG TEXT ============== */
.manifesto {
  max-width: 1400px;
  margin: 0 auto 4rem;
  padding: 0 2.5rem;
  position: relative;
  z-index: 2;
}
.manifesto p {
  font-family: 'Fraunces', serif;
  font-weight: 400;
  font-size: clamp(1.4rem, 2.6vw, 2.2rem);
  line-height: 1.3;
  max-width: 1000px;
  color: var(--ink-soft);
  letter-spacing: -0.01em;
}
.manifesto p em {
  font-style: italic;
  color: var(--accent);
}

/* ============== DIVIDER ============== */
.ornament {
  text-align: center;
  margin: 3rem 0;
  font-family: 'Fraunces', serif;
  color: var(--gold);
  font-size: 1.5rem;
  letter-spacing: 1rem;
}

/* ============== FOOTER ============== */
footer {
  border-top: 1px solid var(--rule);
  padding: 2.5rem;
  text-align: center;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.8rem;
  color: var(--ink-soft);
  position: relative;
  z-index: 2;
  background: var(--paper-deep);
}
footer em {
  color: var(--accent);
  font-family: 'Fraunces', serif;
  font-size: 0.95rem;
  font-style: italic;
}

/* ============== RESPONSIVE ============== */
@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
    gap: 2rem;
    padding: 2rem 1.5rem 4rem;
  }
  aside.toc {
    position: static;
    max-height: none;
    border-right: none;
    border-bottom: 1px solid var(--rule);
    padding-right: 0;
    padding-bottom: 1.5rem;
  }
  .hero { padding: 3rem 1.5rem; }
  nav.topbar {
    padding: 0.8rem 1.2rem;
    flex-wrap: wrap;
    gap: 0.5rem;
  }
  .nav-links { gap: 1rem; flex-wrap: wrap; }
  .nav-links a { font-size: 0.85rem; }
  body { font-size: 17px; }
  .path-grid, .manifesto { padding-left: 1.5rem; padding-right: 1.5rem; }
}

/* scrollbar */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--paper); }
::-webkit-scrollbar-thumb { background: var(--rule); border-radius: 4px; }