/* ============================================================
   SE Interview Guide — styling.
   Palette and type borrowed from cumabolat.com: Inter, a deep
   navy accent on a near-white ground, hairline borders, soft
   shadows. Deliberately plain: no gradients-as-decoration, no
   emoji, restrained colour.
   ============================================================ */

:root {
  --font-sans: "Inter", system-ui, -apple-system, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, monospace;

  --bg: #ffffff;
  --bg-soft: #f3f6fb;
  --text: #0c1a2e;
  --text-body: #33465b;
  --text-muted: #5a6d82;
  --border: #d4dde8;
  --accent: #1e3a5f;
  --accent-hover: #153252;
  --accent-soft: #e4ecf4;
  --accent-text: #153252;

  --easy-bg: #e6f0ea;   --easy-fg: #2f7d5d;
  --med-bg:  #fbf0dd;   --med-fg:  #96661a;
  --hard-bg: #f7e4e4;   --hard-fg: #b23b3b;

  --shadow-sm: 0 1px 2px rgba(12, 26, 46, 0.05);
  --shadow-md: 0 10px 30px rgba(12, 26, 46, 0.10);
  --radius: 12px;
}

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

html { scroll-behavior: smooth; scroll-padding-top: 1.5rem; }

body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--text-body);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  line-height: 1.65;
}

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

/* ---------------- Layout ---------------- */
.layout { min-height: 100vh; }

/* ---------------- Top navigation ---------------- */
.topnav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}
.topnav-inner {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.15rem 1.25rem;
  flex-wrap: wrap;
  width: min(960px, 100%);
  margin: 0 auto;
  padding: 0  clamp(1.2rem, 3vw, 2rem);
}
.topnav-links {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.15rem 1.25rem;
  flex-wrap: wrap;
}
.topnav a.topnav-home {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-muted);
  letter-spacing: -0.01em;
  padding: 0.85rem 0.15rem;
}
.topnav a.topnav-home:hover,
.topnav a.topnav-home.is-active {
  color: var(--text);
}

.topnav-item { position: relative; }
.topnav-item > a.topnav-topic {
  display: inline-block;
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--text-muted);
  padding: 0.85rem 0.15rem;
}
.topnav-item > a.topnav-topic:hover,
.topnav-item.is-open > a.topnav-topic,
.topnav-item > a.topnav-topic.is-active {
  color: var(--text);
}

/* Dropdown flush under the topic; slight overlap so hover never breaks. */
.topnav-drop {
  display: none;
  position: absolute;
  top: calc(100% - 2px);
  left: 50%;
  transform: translateX(-50%);
  min-width: 220px;
  max-height: min(70vh, 420px);
  overflow-y: auto;
  padding: 0.55rem 0;
  margin-top: 0;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: var(--shadow-md);
  z-index: 60;
}
/* Open state is JS-only (.is-open). CSS :hover was reopening after click. */
.topnav-item.is-open > .topnav-drop {
  display: block;
}
.topnav-drop a {
  display: block;
  padding: 0.4rem 0.95rem;
  font-size: 0.88rem;
  font-weight: 400;
  color: var(--text-muted);
  white-space: nowrap;
}
.topnav-drop a:hover,
.topnav-drop a.is-active {
  color: var(--text);
  background: var(--bg-soft);
}
.topnav-drop .drop-label {
  display: block;
  padding: 0.55rem 0.95rem 0.25rem;
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--text-muted);
}
.topnav-drop .drop-label:first-child { padding-top: 0.2rem; }

.topnav-burger {
  display: none;
  margin-left: auto;
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-muted);
  background: none;
  border: 0;
  cursor: pointer;
  padding: 0.85rem 0;
}
.topnav-burger:hover { color: var(--text); }

.topnav-portfolio {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 6px;
  padding: 0.28rem 0.7rem;
  white-space: nowrap;
  margin-left: 0.35rem;
  transition: background 0.12s, color 0.12s;
}
.topnav-portfolio:hover {
  background: var(--accent-soft);
  color: var(--accent-text);
}

@media (max-width: 760px) {
  .topnav-inner {
    justify-content: space-between;
    padding: 0 clamp(1.2rem, 3vw, 2rem);
  }
  .topnav-burger { display: block; }
  .topnav a.topnav-home { padding: 0.85rem 0; }
  .topnav-portfolio {
    order: 2;
    margin-left: auto;
    margin-right: 0.75rem;
  }
  .topnav-burger { order: 3; }
  .topnav-links {
    display: none;
    width: 100%;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding-bottom: 0.6rem;
    order: 4;
  }
  body.nav-open .topnav-links { display: flex; }
  .topnav-item > a.topnav-topic {
    display: block;
    padding: 0.55rem 0;
    border-top: 1px solid var(--border);
  }
  .topnav-drop {
    position: static;
    display: none;
    left: auto;
    transform: none;
    min-width: 0;
    max-height: none;
    border: 0;
    border-radius: 0;
    box-shadow: none;
    padding: 0 0 0.4rem 0.85rem;
    background: transparent;
  }
  .topnav-item.is-open > .topnav-drop { display: block; }
  .topnav-drop a { white-space: normal; padding: 0.35rem 0; }
  .topnav-drop a:hover,
  .topnav-drop a.is-active { background: none; }
}

/* ---------------- Main column (always centered) ---------------- */
main {
  box-sizing: border-box;
  width: min(760px, 100%);
  margin-left: auto;
  margin-right: auto;
  padding: 1.5rem clamp(1.4rem, 4vw, 2rem) 4rem;
}

/* ---------------- Hero ---------------- */
.hero { margin-bottom: 2.6rem; }
.eyebrow {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--accent-text);
  background: var(--accent-soft);
  padding: 0.32rem 0.75rem;
  border-radius: 999px;
  margin-bottom: 1.1rem;
}
.hero h1 {
  font-size: clamp(2rem, 4.2vw, 2.9rem);
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--text);
  margin: 0 0 1rem;
}
.hero p {
  font-size: clamp(1rem, 1.4vw, 1.12rem);
  color: var(--text-muted);
  line-height: 1.7;
  margin: 0;
  max-width: 62ch;
}

/* ---------------- Sections & typography ---------------- */
section { margin: 2.4rem 0; }
section h2 {
  font-size: 1.32rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
  margin: 0 0 0.85rem;
}
h3, h4 { color: var(--text); }
p { margin: 0.7rem 0; }
strong { color: var(--text); font-weight: 700; }

.lead { font-size: 1.05rem; color: var(--text-muted); }

ul, ol { padding-left: 1.3rem; margin: 0.7rem 0; }
li { margin: 0.35rem 0; }

.divider { border: 0; border-top: 1px solid var(--border); margin: 2.6rem 0; }

/* ---------------- Inline code & code blocks ---------------- */
code {
  font-family: var(--font-mono);
  font-size: 0.86em;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  padding: 0.08rem 0.34rem;
  border-radius: 5px;
  color: var(--accent-text);
}
.code-title {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin: 1.3rem 0 0.4rem;
}
pre {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.84rem;
  line-height: 1.6;
  color: #26374a;
  margin: 0.4rem 0 1.4rem;
}
pre code { background: none; border: 0; padding: 0; color: inherit; font-size: inherit; }
pre .kw  { color: #1e3a5f; font-weight: 600; }
pre .str { color: #2f7d5d; }
pre .com { color: #8b99a8; font-style: italic; }
pre .fn  { color: #3457a0; }
pre .cls { color: #8a5a2b; }
pre .num { color: #a6572f; }
pre .dec { color: #6b57a6; }
pre .type { color: #8a5a2b; }

/* ---------------- Callouts ---------------- */
.callout {
  background: var(--accent-soft);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: 8px;
  padding: 0.85rem 1.05rem;
  margin: 1.2rem 0;
  font-size: 0.95rem;
  color: var(--text-body);
}
.callout .t { font-weight: 700; color: var(--accent-text); margin-right: 0.35rem; }
.callout.warn { background: #fdf4e7; border-left-color: #c98a2b; }
.callout.warn .t { color: #9a6a1c; }
.callout.tip { background: #eaf2ee; border-left-color: #2f7d5d; }
.callout.tip .t { color: #2f7d5d; }
.callout.danger { background: #faeaea; border-left-color: #b23b3b; }
.callout.danger .t { color: #b23b3b; }

/* ---------------- Definition lists ---------------- */
.deflist { margin: 1rem 0; border: 1px solid var(--border); border-radius: 10px; overflow: hidden; }
.deflist .row {
  display: grid;
  grid-template-columns: minmax(120px, 210px) 1fr;
  gap: 0.4rem 1.1rem;
  padding: 0.65rem 0.9rem;
  border-bottom: 1px solid var(--border);
}
.deflist .row:last-child { border-bottom: 0; }
.deflist .row:nth-child(even) { background: var(--bg-soft); }
.deflist .k { font-weight: 600; color: var(--text); }
.deflist .v { color: var(--text-body); }

/* ---------------- Tables ---------------- */
.table-wrap { overflow-x: auto; margin: 1rem 0; border: 1px solid var(--border); border-radius: 10px; }
table { border-collapse: collapse; width: 100%; font-size: 0.92rem; }
th, td { text-align: left; padding: 0.6rem 0.85rem; border-bottom: 1px solid var(--border); }
th {
  background: var(--bg-soft);
  font-weight: 700; color: var(--text);
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.04em;
}
td { color: var(--text-body); }
tr:last-child td { border-bottom: 0; }

/* ---------------- ASCII diagrams ---------------- */
.diagram {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.55;
  white-space: pre;
  overflow-x: auto;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem 1.1rem;
  margin: 1.2rem 0;
  color: var(--text-body);
}
.nodebox {
  display: inline-block;
  background: var(--accent-soft);
  color: var(--accent-text);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.02rem 0.4rem;
  font-weight: 600;
}

/* ---------------- Home / topic cards ---------------- */
.topic-grid, .hub-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 14px;
  margin: 1.4rem 0 2rem;
}
a.topic-card, a.hub-card {
  display: flex;
  flex-direction: column;
  gap: 6px;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.15rem 1.25rem;
  box-shadow: var(--shadow-sm);
  transition: transform 0.15s, box-shadow 0.2s, border-color 0.2s;
}
a.topic-card:hover, a.hub-card:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
  box-shadow: var(--shadow-md);
}
a.topic-card h3,
a.hub-card h3,
a.hub-card h4 {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
}
a.topic-card p, a.hub-card p { margin: 0; color: var(--text-muted); font-size: 0.9rem; line-height: 1.5; }
a.topic-card .meta,
a.hub-card .meta {
  margin-top: 0.35rem;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--accent);
}

/* Cross-links row */
.crosslinks { display: flex; flex-wrap: wrap; gap: 0.55rem; margin: 0.6rem 0; }
.crosslinks a {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 0.5rem 1rem;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.crosslinks a:hover { background: var(--accent-soft); border-color: var(--accent); color: var(--accent-text); }

/* ---------------- Interview Q&A ---------------- */
.filter-bar {
  position: sticky;
  top: 0;
  z-index: 5;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  padding: 0.85rem 0;
  margin-bottom: 0.6rem;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}
.filter-bar .label {
  font-size: 0.68rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.07em; color: var(--text-muted); margin-right: 0.2rem;
}
.filter-bar button.chip {
  font-family: inherit; cursor: pointer;
  font-size: 0.82rem; font-weight: 600;
  padding: 0.36rem 0.85rem; border-radius: 999px;
  background: var(--bg); color: var(--text-muted);
  border: 1px solid var(--border);
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.filter-bar button.chip:hover { background: var(--accent-soft); color: var(--accent-text); }
.filter-bar button.chip.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.filter-bar .spacer { flex: 1; }
.filter-bar .count { font-size: 0.82rem; color: var(--text-muted); font-weight: 600; }
.filter-bar button.toggle-all {
  font-family: inherit; cursor: pointer;
  font-size: 0.82rem; font-weight: 600;
  padding: 0.36rem 0.85rem; border-radius: 8px;
  background: var(--bg); color: var(--accent-text);
  border: 1px solid var(--border);
  transition: background 0.15s;
}
.filter-bar button.toggle-all:hover { background: var(--accent-soft); }

.qa-list { display: grid; gap: 0.55rem; margin: 1.2rem 0; }

.qa-item {
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  overflow: hidden;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.qa-item:hover { box-shadow: var(--shadow-sm); }
.qa-item.hidden { display: none; }

.qa-toggle {
  width: 100%;
  display: flex;
  align-items: flex-start;
  gap: 0.7rem;
  text-align: left;
  cursor: pointer;
  font-family: inherit;
  background: transparent;
  border: none;
  padding: 0.85rem 1rem;
  color: var(--text);
}
.qa-toggle:hover { background: var(--bg-soft); }
.qa-toggle .qnum {
  flex-shrink: 0;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-muted);
  min-width: 24px;
  padding-top: 0.2rem;
}
.qa-toggle .diff {
  flex-shrink: 0;
  align-self: flex-start;
  margin-top: 0.05rem;
  font-size: 0.62rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.22rem 0.5rem;
  border-radius: 999px;
  white-space: nowrap;
}
.qa-toggle .qa-q { flex: 1; font-size: 0.98rem; font-weight: 600; line-height: 1.5; }
.qa-toggle .arrow {
  flex-shrink: 0;
  width: 8px; height: 8px;
  margin: 0.45rem 0.2rem 0 0;
  border-right: 2px solid var(--text-muted);
  border-bottom: 2px solid var(--text-muted);
  transform: rotate(-45deg);
  transition: transform 0.18s;
}
.qa-toggle[aria-expanded="true"] .arrow { transform: rotate(45deg); }

.diff.easy { background: var(--easy-bg); color: var(--easy-fg); }
.diff.med  { background: var(--med-bg);  color: var(--med-fg); }
.diff.hard { background: var(--hard-bg); color: var(--hard-fg); }

.qa-a {
  padding: 0.2rem 1.1rem 1.05rem;
  border-top: 1px solid var(--border);
  background: var(--bg-soft);
  font-size: 0.95rem;
  color: var(--text-body);
}
.qa-a[hidden] { display: none; }
.qa-a p:first-child { margin-top: 0.8rem; }
.qa-a p { margin: 0.5rem 0; line-height: 1.65; }
.qa-a ul, .qa-a ol { margin: 0.5rem 0; padding-left: 1.3rem; }

/* ---------------- Page nav + site footer ---------------- */
.page-nav {
  margin: 2.5rem 0 0;
  padding-top: 1.2rem;
  border-top: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-muted);
}
.page-nav a { font-weight: 600; }

.site-footer {
  margin-top: 0;
  padding: 1.5rem clamp(1.4rem, 4vw, 2rem) 2.2rem;
  border-top: 1px solid var(--border);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}
.site-footer p { margin: 0; }

/* Legacy footer selector kept for any leftover markup */
footer:not(.site-footer) {
  margin-top: 2.5rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.85rem;
}
footer:not(.site-footer) p { margin: 0.3rem 0; }

.to-top {
  position: fixed;
  right: 1.4rem;
  bottom: 1.4rem;
  width: 40px; height: 40px;
  display: grid; place-items: center;
  border: 1px solid var(--accent);
  border-radius: 10px;
  background: var(--accent);
  color: #fff;
  font-size: 1rem;
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity 0.2s, transform 0.2s, background 0.15s;
  box-shadow: var(--shadow-md);
}
.to-top.show { opacity: 1; pointer-events: auto; transform: none; }
.to-top:hover { background: var(--accent-hover); }

/* ---------------- Home / topic index pages ---------------- */
.layout--home main {
  max-width: 760px;
  padding: 1.75rem clamp(1.4rem, 5vw, 2.5rem) 4rem;
  text-align: center;
}
.layout--home .hero { margin-bottom: 2.8rem; }
.layout--home .hero p,
.layout--home .lead { margin-left: auto; margin-right: auto; }
.layout--home .topic-card,
.layout--home .hub-card { text-align: left; }
.layout--home .crosslinks { justify-content: center; }
.layout--home .page-nav,
.layout--home footer:not(.site-footer) { text-align: center; }
.layout--home section h2 { text-align: center; }

/* ---------------- Responsive ---------------- */
@media (max-width: 860px) {
  .filter-bar { position: static; }
  .deflist .row { grid-template-columns: 1fr; gap: 0.15rem; }
}