/* =========================================================================
   StackSimplified · Interview Prep — book.css
   A calm, readable "book" theme with light/dark support.
   ========================================================================= */

:root {
  --accent: #b45309;         /* warm amber — a "study book" feel */
  --accent-2: #0e7490;
  --accent-grad: linear-gradient(135deg, #b45309 0%, #d97706 100%);

  --bg: #fbfaf7;             /* warm paper */
  --bg-soft: #f3f1ea;
  --surface: #ffffff;
  --border: #e7e3d8;
  --text: #1f2430;
  --text-soft: #55606f;
  --text-muted: #8a93a2;
  --code-bg: #1b2130;
  --code-text: #e7ecf5;
  --shadow: 0 1px 2px rgba(31, 36, 48, 0.05), 0 10px 30px rgba(31, 36, 48, 0.06);
  --shadow-lg: 0 16px 48px rgba(31, 36, 48, 0.14);

  --maxw: 1180px;
  --read-w: 720px;
  --radius: 16px;
  --radius-sm: 10px;
  --nav-h: 62px;

  --font-ui: "Inter", system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  --font-read: "Lora", Georgia, "Times New Roman", serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
}

:root[data-theme="dark"] {
  --bg: #0f1420;
  --bg-soft: #151b2b;
  --surface: #151b2b;
  --border: #26304a;
  --text: #eef2fb;
  --text-soft: #b7c0d6;
  --text-muted: #7b859e;
  --code-bg: #080c16;
  --code-text: #d8e0f2;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 10px 30px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.5);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font-ui);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  transition: background 0.25s ease, color 0.25s ease;
}
a { color: inherit; text-decoration: none; }

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* ---------------------------- Nav bar ---------------------------------- */
.nav {
  position: sticky; top: 0; z-index: 50; height: var(--nav-h);
  display: flex; align-items: center;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav__inner { display: flex; align-items: center; justify-content: space-between; width: 100%; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 1.02rem; letter-spacing: -0.02em; }
.brand__logo {
  width: 34px; height: 34px; border-radius: 9px; background: var(--accent-grad);
  display: grid; place-items: center; color: #fff; font-size: 1.05rem; box-shadow: var(--shadow);
}
.brand__sub { color: var(--text-muted); font-weight: 600; }
.nav__controls { display: flex; align-items: center; gap: 10px; }
.theme-toggle {
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  width: 40px; height: 40px; border-radius: 999px; cursor: pointer; font-size: 1.05rem;
  display: grid; place-items: center; transition: transform 0.15s ease, background 0.15s ease;
}
.theme-toggle:hover { transform: translateY(-1px); background: var(--bg-soft); }
.hamburger {
  width: 42px; height: 42px; border-radius: 12px; border: 1px solid var(--border);
  background: var(--surface); cursor: pointer; display: none; place-items: center; gap: 5px; padding: 0;
}
.hamburger span { display: block; width: 18px; height: 2px; border-radius: 2px; background: var(--text); }

/* ---------------------------- Buttons ---------------------------------- */
.btn {
  display: inline-flex; align-items: center; gap: 8px; padding: 12px 22px; border-radius: 999px;
  font-weight: 700; font-size: 0.95rem; cursor: pointer; border: 1px solid transparent;
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.15s ease; font-family: inherit;
}
.btn--primary { background: var(--accent-grad); color: #fff; box-shadow: var(--shadow); }
.btn--primary:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); }
.btn--ghost { background: var(--surface); border-color: var(--border); color: var(--text); }
.btn--ghost:hover { background: var(--bg-soft); }

/* ---------------------------- Cover / hero ----------------------------- */
.cover { padding: 68px 0 40px; }
.cover__badge {
  display: inline-flex; align-items: center; gap: 8px; padding: 6px 14px; border-radius: 999px;
  background: color-mix(in srgb, var(--accent) 10%, transparent); color: var(--accent);
  font-weight: 600; font-size: 0.85rem; border: 1px solid color-mix(in srgb, var(--accent) 22%, transparent);
}
.cover__title {
  font-family: var(--font-read); font-size: clamp(2rem, 4.6vw, 3.2rem); line-height: 1.12;
  letter-spacing: -0.01em; font-weight: 600; margin: 20px 0 14px;
}
.cover__sub { max-width: 640px; font-size: 1.12rem; color: var(--text-soft); margin: 0 0 26px; }
.cover__cta { display: flex; gap: 14px; flex-wrap: wrap; }

/* ---------------------------- Day cards -------------------------------- */
.section { padding: 40px 0; }
.section__head { margin-bottom: 26px; }
.section__eyebrow { text-transform: uppercase; letter-spacing: 0.12em; font-size: 0.76rem; font-weight: 700; color: var(--accent); }
.section__title { font-family: var(--font-read); font-size: clamp(1.5rem, 3vw, 2.1rem); font-weight: 600; margin: 6px 0 8px; }
.section__desc { color: var(--text-soft); max-width: 640px; }

.days { display: grid; gap: 18px; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); }
.daycard {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 24px; box-shadow: var(--shadow); cursor: pointer; display: flex; flex-direction: column;
  gap: 10px; height: 100%; transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.daycard:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.daycard__num {
  width: 46px; height: 46px; border-radius: 12px; background: var(--accent-grad); color: #fff;
  display: grid; place-items: center; font-weight: 800; font-size: 1.05rem;
}
.daycard__kicker { font-size: 0.74rem; text-transform: uppercase; letter-spacing: 0.1em; font-weight: 700; color: var(--text-muted); }
.daycard__title { font-family: var(--font-read); font-size: 1.3rem; font-weight: 600; letter-spacing: -0.01em; }
.daycard__desc { color: var(--text-soft); font-size: 0.96rem; flex: 1; }
.daycard__meta { display: flex; gap: 12px; color: var(--text-muted); font-size: 0.84rem; font-weight: 600; }
.tag {
  display: inline-block; padding: 3px 10px; border-radius: 999px; font-size: 0.76rem; font-weight: 600;
  background: var(--bg-soft); color: var(--text-soft); border: 1px solid var(--border);
}

/* ---------------------------- Reader layout ---------------------------- */
.reader { display: grid; grid-template-columns: 280px 1fr; gap: 40px; align-items: start; padding: 8px 0 30px; }

/* table of contents */
.toc {
  position: sticky; top: calc(var(--nav-h) + 16px); align-self: start;
  max-height: calc(100vh - var(--nav-h) - 32px); overflow-y: auto;
}
.toc__back { display: inline-block; color: var(--text-muted); font-weight: 600; font-size: 0.85rem; margin-bottom: 12px; }
.toc__back:hover { color: var(--accent); }
.toc-day { border: 1px solid var(--border); border-radius: 14px; background: var(--surface); margin-bottom: 12px; overflow: hidden; box-shadow: var(--shadow); }
.toc-day--current { border-color: color-mix(in srgb, var(--accent) 45%, var(--border)); }
.toc-day__head {
  display: flex; align-items: center; gap: 12px; width: 100%; text-align: left; border: none;
  background: transparent; cursor: pointer; padding: 12px 14px; font-family: inherit; transition: background 0.15s ease;
}
.toc-day__head:hover { background: var(--bg-soft); }
.toc-day--current .toc-day__head { background: color-mix(in srgb, var(--accent) 8%, transparent); }
.toc-day__badge {
  flex-shrink: 0; width: 34px; height: 34px; border-radius: 10px; background: var(--accent-grad); color: #fff;
  font-weight: 800; font-size: 0.8rem; display: grid; place-items: center;
}
.toc-day__meta { display: flex; flex-direction: column; gap: 1px; flex: 1; min-width: 0; }
.toc-day__label { font-size: 0.64rem; text-transform: uppercase; letter-spacing: 0.11em; font-weight: 700; color: var(--accent); }
.toc-day__name { font-size: 0.92rem; font-weight: 700; line-height: 1.25; }
.toc-day__chev { flex-shrink: 0; color: var(--text-muted); font-size: 1.05rem; transition: transform 0.2s ease; }
.toc-day__chev--open { transform: rotate(180deg); }
.toc-chapters { list-style: none; margin: 0; padding: 4px 10px 10px 16px; border-top: 1px solid var(--border); }
.toc-chapter {
  display: flex; align-items: flex-start; gap: 8px; width: 100%; text-align: left; border: none;
  background: transparent; cursor: pointer; font-family: inherit; padding: 8px 10px; border-radius: 9px;
  border-left: 2px solid var(--border); color: var(--text-soft);
  transition: background 0.12s ease, color 0.12s ease, border-color 0.12s ease;
}
.toc-chapter:hover { background: var(--bg-soft); color: var(--text); }
.toc-chapter--active { background: color-mix(in srgb, var(--accent) 13%, transparent); border-left-color: var(--accent); color: var(--accent); }
.toc-chapter__num { flex-shrink: 0; font-family: var(--font-mono); font-size: 0.74rem; font-weight: 600; opacity: 0.7; padding-top: 1px; }
.toc-chapter__title { font-size: 0.88rem; line-height: 1.4; font-weight: 500; }
.toc-chapter--active .toc-chapter__title { font-weight: 700; }

/* reading pane */
.page { min-width: 0; max-width: var(--read-w); }
.page__crumbs { display: flex; gap: 8px; align-items: center; color: var(--text-muted); font-size: 0.88rem; font-weight: 600; padding: 20px 0 6px; }
.page__crumbs a:hover { color: var(--accent); }
.page__head { padding: 10px 16px; margin: 6px 0 20px; background: var(--bg-soft); border: 1px solid var(--border); border-radius: 12px;
  display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; }
.page__daytag { display: flex; align-items: center; gap: 10px; }
.page__daybadge { background: var(--accent-grad); color: #fff; font-weight: 700; font-size: 0.78rem; padding: 4px 11px; border-radius: 999px; white-space: nowrap; }
.page__dayname { font-weight: 700; font-size: 0.95rem; }
.page__kicker { font-family: var(--font-mono); font-size: 0.82rem; font-weight: 600; color: var(--text-muted); }
.page__title { font-family: var(--font-read); font-size: clamp(1.7rem, 3.4vw, 2.4rem); font-weight: 600; letter-spacing: -0.01em; margin: 4px 0 6px; line-height: 1.15; }
.page__blurb { color: var(--text-soft); font-size: 1.06rem; margin: 0 0 22px; padding-left: 14px; border-left: 3px solid color-mix(in srgb, var(--accent) 40%, transparent); font-style: italic; }

/* prose (book reading) */
.prose { font-family: var(--font-read); font-size: 1.12rem; line-height: 1.85; color: var(--text); margin: 0 0 18px; }
.prose strong { font-weight: 600; }
.h2 { font-family: var(--font-read); font-size: 1.5rem; font-weight: 600; margin: 30px 0 10px; letter-spacing: -0.01em; }
.prose-list { font-family: var(--font-read); margin: 0 0 18px; padding-left: 24px; line-height: 1.9; color: var(--text); }
.prose-list li { margin-bottom: 6px; }
.analogy {
  display: flex; gap: 14px; align-items: flex-start;
  background: color-mix(in srgb, var(--accent-2) 9%, transparent);
  border: 1px solid color-mix(in srgb, var(--accent-2) 28%, transparent);
  border-radius: var(--radius-sm); padding: 16px 18px; margin: 16px 0 22px;
}
.analogy__icon { font-size: 1.3rem; }
.analogy__body { }
.analogy__label { font-weight: 700; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--accent-2); margin-bottom: 4px; }
.analogy p { margin: 0; font-family: var(--font-read); font-size: 1.05rem; line-height: 1.7; }
.note {
  display: flex; gap: 12px; align-items: flex-start; background: color-mix(in srgb, var(--accent) 9%, transparent);
  border: 1px solid color-mix(in srgb, var(--accent) 26%, transparent); border-radius: var(--radius-sm);
  padding: 14px 16px; margin: 14px 0 22px;
}
.note p { margin: 0; font-size: 0.99rem; line-height: 1.6; }

/* key term */
.term { background: color-mix(in srgb, var(--accent) 14%, transparent); border-radius: 5px; padding: 0 5px; font-weight: 600; }

/* code */
pre.code {
  background: var(--code-bg); color: var(--code-text); border-radius: var(--radius-sm);
  padding: 16px 18px; overflow-x: auto; font-family: var(--font-mono); font-size: 0.86rem; line-height: 1.6; margin: 14px 0 20px;
}

/* interview one-liner card */
.answer {
  background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--accent);
  border-radius: var(--radius-sm); padding: 16px 18px; margin: 16px 0 22px; box-shadow: var(--shadow);
}
.answer__label { font-weight: 700; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--accent); margin-bottom: 6px; display: flex; gap: 8px; }
.answer p { margin: 0; font-size: 1.02rem; line-height: 1.65; }

/* ---------------------------- MCQ -------------------------------------- */
.mcq { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 22px 18px; margin: 22px 0; box-shadow: var(--shadow); }
.mcq__tag { display: inline-block; font-size: 0.72rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.09em; color: var(--accent-2); margin-bottom: 8px; }
.mcq__q { font-weight: 600; font-size: 1.06rem; margin: 0 0 14px; line-height: 1.5; }
.mcq__opts { display: grid; gap: 10px; }
.mcq__opt {
  display: flex; gap: 12px; align-items: flex-start; text-align: left; width: 100%; border: 1px solid var(--border);
  background: var(--bg); border-radius: 10px; padding: 12px 14px; cursor: pointer; font-family: inherit;
  font-size: 0.98rem; color: var(--text); transition: background 0.12s ease, border-color 0.12s ease;
}
.mcq__opt:hover { background: var(--bg-soft); }
.mcq__opt:disabled { cursor: default; }
.mcq__opt--correct { border-color: #16a34a; background: color-mix(in srgb, #16a34a 12%, transparent); }
.mcq__opt--wrong { border-color: #dc2626; background: color-mix(in srgb, #dc2626 10%, transparent); }
.mcq__letter {
  flex-shrink: 0; width: 26px; height: 26px; border-radius: 7px; background: var(--bg-soft);
  border: 1px solid var(--border); display: grid; place-items: center; font-weight: 700; font-size: 0.85rem;
}
.mcq__opt--correct .mcq__letter { background: #16a34a; color: #fff; border-color: #16a34a; }
.mcq__opt--wrong .mcq__letter { background: #dc2626; color: #fff; border-color: #dc2626; }
.mcq__explain {
  margin-top: 14px; padding: 14px 16px; border-radius: 10px; background: var(--bg-soft);
  border: 1px solid var(--border); font-size: 0.97rem; line-height: 1.6;
}
.mcq__explain strong { color: var(--accent); }

/* ---------------------------- Chapter nav ------------------------------ */
.chapter-nav { display: flex; justify-content: space-between; gap: 12px; margin: 34px 0 20px; flex-wrap: wrap; border-top: 1px solid var(--border); padding-top: 22px; }

/* ---------------------------- Footer ----------------------------------- */
.footer { border-top: 1px solid var(--border); margin-top: 50px; padding: 30px 0; color: var(--text-muted); font-size: 0.9rem; }
.footer__inner { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 12px; }

/* ---------------------------- Drawer (mobile) -------------------------- */
.drawer__backdrop { position: fixed; inset: 0; background: rgba(15,20,32,0.45); z-index: 90; backdrop-filter: blur(2px); }
.drawer { position: fixed; top: 0; right: 0; height: 100vh; width: min(320px, 86vw); background: var(--surface);
  border-left: 1px solid var(--border); box-shadow: var(--shadow-lg); z-index: 100; padding: 74px 16px 24px; overflow-y: auto; }

/* ---------------------------- Responsive ------------------------------- */
@media (max-width: 900px) {
  .reader { grid-template-columns: 1fr; }
  .toc { position: static; max-height: none; order: 1; margin-bottom: 18px; }
  .page { order: 2; max-width: 100%; }
  .hamburger { display: grid; }
}