/* ---------- Top nav (Jakob's Law: familiar patterns) ---------- */
.nav{
  position: sticky; top: 0; z-index: 30;
  backdrop-filter: blur(12px);
  background: linear-gradient(180deg, rgba(6,31,39,.85), rgba(6,31,39,.55));
  border-bottom: 1px solid rgba(255,255,255,.08);
  border-radius: 0 0 22px 22px;
  overflow: hidden;
}
.nav-inner{
  display: flex; align-items: center; justify-content: space-between;
  padding: var(--space-2) 0;
  gap: var(--space-2);
}
.brand{
  display: inline-flex; align-items: center; gap: 10px;
  font-weight: 600; letter-spacing: .2px;
}
.dot{
  width: 10px; height: 10px; border-radius: 999px;
  background: radial-gradient(circle at 30% 30%, var(--gold2), var(--gold));
  box-shadow: 0 0 24px rgba(216,177,90,.45);
}
.links{
  display: flex; align-items: center; gap: clamp(10px, 2.2vw, 22px);
  color: var(--muted);
  font-size: 14px;
}
.links a{ padding: 8px 10px; border-radius: 12px; }
.links a:hover{ background: rgba(255,255,255,.06); color: var(--text); }

.cta{
  display: inline-flex; align-items: center; justify-content: center;
  gap: 10px;
  padding: 12px 16px;
  border-radius: 999px;
  border: 1px solid rgba(216,177,90,.35);
  background: linear-gradient(180deg, rgba(216,177,90,.18), rgba(216,177,90,.08));
  color: var(--text);
  font-weight: 600;
  transition: transform 120ms cubic-bezier(.2,.8,.2,1), box-shadow 140ms cubic-bezier(.2,.8,.2,1), background-color 140ms, border-color 140ms, color 140ms;
  white-space: nowrap;
}
.cta:hover{
  transform: translateY(-1px);
  border-color: rgba(216,177,90,.55);
  background: linear-gradient(180deg, rgba(216,177,90,.22), rgba(216,177,90,.10));
}

/* ---------- Hero (Fitts + Von Restorff + Visual Hierarchy) ---------- */
header.hero{
  padding: var(--space-6) 0 var(--space-3);
}
.hero-grid{
  display: grid;
  grid-template-columns: 1.15fr .85fr; /* golden-ish balance */
  gap: var(--space-5);
  align-items: center;
}
.kicker{
  display: inline-flex; align-items: center; gap: 10px;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid rgba(255,255,255,.12);
  background: rgba(255,255,255,.05);
  color: var(--muted);
  font-size: 13px;
  width: fit-content;
}
.kicker strong{ color: var(--stardust); font-weight: 600; }
h1{
  font-size: var(--h1);
  letter-spacing: -0.03em;
  line-height: 1.05;
  margin: var(--space-2) 0 var(--space-2);
}
.sub{
  font-size: var(--p);
  color: var(--muted);
  max-width: 62ch;
  margin: 0 0 var(--space-3);
}
.meta-note{
  font-size: 13px;
  color: var(--muted2);
  margin: var(--space-2) 0 0;
  line-height: 1.5;
  max-width: 62ch;
}
.hero-actions{
  display: flex; flex-wrap: wrap; align-items: center;
  gap: var(--space-2);
  margin-top: var(--space-2);
}
.ghost{
  display: inline-flex; align-items: center; justify-content: center;
  padding: 12px 16px;
  border-radius: 999px;
  border: 1px solid rgba(255,255,255,.14);
  background: rgba(255,255,255,.04);
  color: var(--text);
  font-weight: 600;
  transition: transform 120ms cubic-bezier(.2,.8,.2,1), box-shadow 140ms cubic-bezier(.2,.8,.2,1), background-color 140ms, border-color 140ms, color 140ms;
}
.ghost:hover{ background: rgba(255,255,255,.06); }

.micro{
  display: flex; flex-wrap: wrap; gap: 9px 12px;
  margin-top: var(--space-3);
  color: var(--muted2);
  font-size: 13px;
}
.micro > span{
  display: inline-flex; align-items: center; gap: 8px;
  padding: 7px 10px;
  border: 1px solid rgba(255,255,255,.10);
  background: rgba(255,255,255,.03);
  border-radius: 999px;
  letter-spacing: 0.03em;
}
.check{
  width: 16px; height: 16px;
  border-radius: 999px;
  background: radial-gradient(circle at 35% 35%, rgba(242,213,139,.85), rgba(216,177,90,.28) 60%, rgba(7,43,54,.35) 100%);
  border: 1px solid rgba(216,177,90,.55);
  color: var(--gold2);
  display: inline-grid; place-items: center;
  box-shadow: 0 0 18px rgba(216,177,90,.35), inset 0 0 6px rgba(231,245,255,.18);
  flex: 0 0 auto;
}
.check svg{ width: 16px; height: 16px; color: rgba(231,245,255,.88); }

.cover-card{
  position: relative;
  overflow: hidden;
  border: 1px solid rgba(255,255,255,.12);
  padding: 26px 24px 28px;
  border-radius: 28px 28px 34px 34px;
  background:
    radial-gradient(140% 110% at 50% -10%, rgba(255,255,255,.08), transparent 55%),
    linear-gradient(180deg, rgba(10,45,58,.55), rgba(6,25,34,.92));
  box-shadow:
    inset 0 1px 0 rgba(255,255,255,.12),
    0 40px 120px rgba(0,0,0,.55);
  transform: translateZ(0);
}
.cover-card::before{
  content:"";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background:
    radial-gradient(120% 60% at 50% 0%, rgba(255,255,255,.10), transparent 55%);
  pointer-events: none;
}
.cover-card img{
  display: block;
  width: 100%;
  height: clamp(320px, 46vw, 560px);
  aspect-ratio: 4 / 5;
  object-fit: contain;
  object-position: center;
  background:
    radial-gradient(900px 520px at 50% 35%, rgba(216,177,90,.10), transparent 60%),
    linear-gradient(180deg, rgba(7,43,54,.45), rgba(6,31,39,.10));
  margin: 12px auto 6px;
  border-radius: 18px;
  filter:
    drop-shadow(0 22px 44px rgba(0,0,0,.55))
    drop-shadow(0 0 38px rgba(255,190,90,.25));
}
.cover-meta{
  padding: var(--space-2);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-2);
  color: var(--muted2);
  font-size: 13px;
}
.cover-meta .isbn{
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1, "lnum" 1;
  letter-spacing: 0.15px;
  opacity: 0.84;
  font-weight: 560;
  transform: translateY(-2px);
}
.cover-meta .isbn-label{
  opacity: 0.65;
  font-weight: 520;
}
.cover-meta .isbn-sep{
  opacity: 0.55;
  margin: 0 6px 0 2px;
}
.cover-meta .isbn-value{
  opacity: 0.92;
  font-weight: 620;
}
.pill{
  padding: 8px 10px;
  border-radius: 999px;
  border: 1px solid rgba(255,255,255,.12);
  background: rgba(255,255,255,.04);
  color: var(--text);
  font-weight: 600;
  font-size: 12px;
}

/* ---------- Sections ---------- */
section{
  padding: var(--space-5) 0;
  /* Prevent bottom browser UI from covering content on mobile */
  scroll-margin-top: 90px;
}
.hero + section{
  padding-top: var(--space-4);
}
.section-head{
  display: grid;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}
h2{
  font-size: var(--h2);
  letter-spacing: -0.02em;
  margin: 0;
}
.lead{
  font-size: var(--p);
  color: var(--muted);
  margin: 0;
  max-width: 70ch;
}

.grid3{
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
}
.card{
  border-radius: var(--radius);
  border: 1px solid var(--stroke-soft);
  background: linear-gradient(180deg, var(--glass-tint-top), var(--glass-tint-bot));
  padding: var(--space-3);
  box-shadow: var(--shadow-card);
  min-height: 100%;
}
.card h3{
  font-size: var(--h3);
  margin: 0 0 10px;
  letter-spacing: -0.01em;
}
.card p{ margin: 0; color: var(--muted); font-size: 15px; }
.publisher-block{
  margin-top: 10px;
  line-height: 1.6;
  color: var(--muted);
}
.publisher-name{
  color: var(--text);
  font-weight: 650;
}
.info-heading{
  margin: 0 0 8px;
  font-size: 14px;
  letter-spacing: -0.01em;
}
.info-rows{
  display: grid;
  gap: 10px;
  font-size: 15px;
  color: var(--muted);
}
.info-row{
  display: flex;
  justify-content: space-between;
  gap: 14px;
}
.info-key{
  color: var(--muted);
}
.info-val{
  color: var(--text);
  font-weight: 650;
  text-align: right;
  text-decoration: none;
}
.info-divider{
  height: 1px;
  background: linear-gradient(90deg, rgba(231,245,255,.08), rgba(231,245,255,.02));
  margin: var(--space-2) 0;
}
.note-muted{
  margin: 0;
  color: var(--muted2);
  font-size: 13px;
}

.icon{
  width: 44px; height: 44px; border-radius: 16px;
  display: grid; place-items: center;
  background: rgba(216,177,90,.10);
  border: 1px solid rgba(216,177,90,.22);
  margin-bottom: var(--space-2);
  box-shadow: 0 0 34px rgba(216,177,90,.16);
}
.icon svg{ width: 22px; height: 22px; opacity: .95; }

/* ---------- Comparison strip ---------- */
.strip{
  border: 1px solid var(--stroke-soft);
  border-radius: var(--radius-lg);
  background: radial-gradient(900px 320px at 20% 20%, rgba(216,177,90,.12), transparent 60%),
              linear-gradient(180deg, var(--glass-tint-top), var(--glass-tint-bot));
  padding: var(--space-4);
  box-shadow: var(--shadow-soft);
}
.strip-grid{
  display: grid;
  grid-template-columns: 1.1fr .9fr;
  gap: var(--space-4);
  align-items: center;
}
.bullets{
  margin: 0; padding: 0; list-style: none;
  display: grid; gap: 12px;
  color: var(--muted);
  font-size: 15px;
}
.bullets li{
  display: grid; grid-template-columns: 18px 1fr;
  gap: 10px; align-items: start;
}
.bullets .mark{
  width: 18px; height: 18px; border-radius: 999px;
  background: radial-gradient(circle at 35% 35%, rgba(242,213,139,.35), rgba(216,177,90,.12) 60%, rgba(7,43,54,.35) 100%);
  border: 1px solid rgba(216,177,90,.28);
  box-shadow: 0 0 16px rgba(216,177,90,.18), inset 0 0 6px rgba(231,245,255,.18);
  color: var(--stardust);
  display: grid; place-items: center;
  margin-top: 2px;
}

/* ---------- FAQ (Progressive disclosure) ---------- */
details{
  border-radius: var(--radius);
  border: 1px solid var(--stroke-soft);
  background: linear-gradient(180deg, var(--glass-tint-top), rgba(7,43,54,.28));
  padding: var(--space-2) var(--space-3);
  overflow: hidden;
}
details + details{ margin-top: 12px; }
summary{
  cursor: pointer;
  list-style: none;
  font-weight: 650;
  letter-spacing: -0.01em;
  padding: 14px 0;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  -webkit-tap-highlight-color: transparent;
}
summary:active{ opacity: .92; }
summary::-webkit-details-marker{ display: none; }
.chev{
  width: 22px; height: 22px;
  border-radius: 999px;

  display: grid; place-items: center;
  color: var(--muted);
  flex: 0 0 auto;
  transform: translateY(-1px);
  transition: transform .2s ease;
}
details[open] .chev{ transform: translateY(-1px) rotate(180deg); }
details p{
  margin: 0 0 12px;
  color: var(--muted);
  font-size: 15px;
  max-width: 85ch;
}

/* ---------- Footer ---------- */
footer{
  position: relative;
  padding: var(--space-5) 0 var(--space-4);
  color: var(--muted2);
  font-size: 13px;
  padding-bottom: calc(var(--space-4) + var(--safe-b));
}
footer::before{
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(231,245,255,.18), transparent);
}
.foot-grid{
  display: grid;
  grid-template-columns: 1.3fr .7fr;
  gap: var(--space-4);
  align-items: start;
}
.fineprint{ max-width: 90ch; }
.foot-actions{
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 10px;
  text-align: right;
}
.foot-link{
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 7px 12px;
  border-radius: 999px;
  border: 1px solid rgba(255,255,255,.10);
  background: rgba(255,255,255,.03);
  color: var(--muted2);
  font-size: 13px;
}
.foot-link:hover{
  background: rgba(255,255,255,.06);
  color: var(--text);
}

/* Prevent buttons near the bottom from being obscured by mobile browser UI */
#buy, #faq{ padding-bottom: calc(var(--space-5) + var(--safe-b)); }