/* ═══════════════════════════════════════════════════════
   EPUB Cover Changer — Apple Liquid Glass
   ═══════════════════════════════════════════════════════ */

/* ── Tokens ─────────────────────────────────────────── */
:root {
  --bg: oklch(97% 0.006 260);
  --bg-mesh-1: oklch(94% 0.02 240 / 0.5);
  --bg-mesh-2: oklch(95% 0.018 300 / 0.3);
  --bg-mesh-3: oklch(96% 0.015 180 / 0.25);
  --surface: oklch(100% 0 0 / 0.72);
  --surface-hover: oklch(100% 0 0 / 0.82);
  --surface-solid: oklch(98% 0.004 260);
  --fg: oklch(17% 0.016 260);
  --muted: oklch(46% 0.016 260);
  --muted-2: oklch(60% 0.012 260);
  --border: oklch(100% 0 0 / 0.55);
  --border-strong: oklch(88% 0.01 260 / 0.8);
  --accent: oklch(57% 0.20 258);
  --accent-hover: oklch(52% 0.22 258);
  --accent-soft: oklch(94% 0.04 258);
  --success: oklch(52% 0.17 155);
  --success-soft: oklch(94% 0.04 155);
  --purple: oklch(55% 0.18 300);
  --purple-soft: oklch(94% 0.04 300);
  --on-accent: oklch(100% 0 0);

  --glass-blur: blur(28px) saturate(1.8);
  --glass-bg: oklch(100% 0 0 / 0.68);
  --glass-bg-strong: oklch(100% 0 0 / 0.80);
  --glass-border: 1px solid oklch(100% 0 0 / 0.50);
  --glass-shadow: 0 2px 20px oklch(0% 0 0 / 0.06), 0 0.5px 0.5px oklch(0% 0 0 / 0.04);
  --glass-shadow-lg: 0 8px 40px oklch(0% 0 0 / 0.08), 0 2px 8px oklch(0% 0 0 / 0.04);
  --glass-shadow-xl: 0 16px 64px oklch(0% 0 0 / 0.10), 0 4px 16px oklch(0% 0 0 / 0.06);
  --glass-highlight: inset 0 1px 0 oklch(100% 0 0 / 0.6);

  --font-display: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Inter', system-ui, sans-serif;
  --font-body: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Inter', system-ui, sans-serif;
  --font-mono: 'SF Mono', ui-monospace, 'JetBrains Mono', 'Cascadia Code', Menlo, monospace;

  --fs-h1: clamp(34px, 5vw, 56px);
  --fs-h2: clamp(24px, 3.2vw, 36px);
  --fs-h3: 19px;
  --fs-lead: 17px;
  --fs-body: 15px;
  --fs-sm: 13px;
  --fs-xs: 11px;
  --gap-xs: 6px;
  --gap-sm: 10px;
  --gap-md: 18px;
  --gap-lg: 28px;
  --gap-xl: 48px;
  --gap-2xl: 80px;
  --container: 1080px;
  --gutter: 24px;
  --radius: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --radius-pill: 999px;
}

/* ── Dark theme ─────────────────────────────────────── */
[data-theme="dark"] {
  --bg: oklch(14% 0.014 260);
  --bg-mesh-1: oklch(20% 0.03 240 / 0.3);
  --bg-mesh-2: oklch(18% 0.025 300 / 0.2);
  --bg-mesh-3: oklch(16% 0.02 180 / 0.15);
  --surface: oklch(22% 0.014 260 / 0.65);
  --surface-hover: oklch(26% 0.014 260 / 0.75);
  --surface-solid: oklch(18% 0.014 260);
  --fg: oklch(95% 0.006 260);
  --muted: oklch(60% 0.014 260);
  --muted-2: oklch(48% 0.012 260);
  --border: oklch(100% 0 0 / 0.10);
  --border-strong: oklch(100% 0 0 / 0.16);
  --accent: oklch(68% 0.18 258);
  --accent-hover: oklch(73% 0.16 258);
  --accent-soft: oklch(22% 0.04 258);
  --success: oklch(68% 0.15 155);
  --success-soft: oklch(20% 0.04 155);
  --purple: oklch(68% 0.16 300);
  --purple-soft: oklch(22% 0.04 300);
  --on-accent: oklch(100% 0 0);

  --glass-bg: oklch(22% 0.014 260 / 0.55);
  --glass-bg-strong: oklch(22% 0.014 260 / 0.70);
  --glass-border: 1px solid oklch(100% 0 0 / 0.10);
  --glass-shadow: 0 2px 20px oklch(0% 0 0 / 0.3), 0 0.5px 0.5px oklch(0% 0 0 / 0.2);
  --glass-shadow-lg: 0 8px 40px oklch(0% 0 0 / 0.4), 0 2px 8px oklch(0% 0 0 / 0.25);
  --glass-shadow-xl: 0 16px 64px oklch(0% 0 0 / 0.5), 0 4px 16px oklch(0% 0 0 / 0.3);
  --glass-highlight: inset 0 1px 0 oklch(100% 0 0 / 0.08);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: oklch(14% 0.014 260);
    --bg-mesh-1: oklch(20% 0.03 240 / 0.3);
    --bg-mesh-2: oklch(18% 0.025 300 / 0.2);
    --bg-mesh-3: oklch(16% 0.02 180 / 0.15);
    --surface: oklch(22% 0.014 260 / 0.65);
    --surface-hover: oklch(26% 0.014 260 / 0.75);
    --surface-solid: oklch(18% 0.014 260);
    --fg: oklch(95% 0.006 260);
    --muted: oklch(60% 0.014 260);
    --muted-2: oklch(48% 0.012 260);
    --border: oklch(100% 0 0 / 0.10);
    --border-strong: oklch(100% 0 0 / 0.16);
    --accent: oklch(68% 0.18 258);
    --accent-hover: oklch(73% 0.16 258);
    --accent-soft: oklch(22% 0.04 258);
    --success: oklch(68% 0.15 155);
    --success-soft: oklch(20% 0.04 155);
    --purple: oklch(68% 0.16 300);
    --purple-soft: oklch(22% 0.04 300);
    --on-accent: oklch(100% 0 0);
    --glass-bg: oklch(22% 0.014 260 / 0.55);
    --glass-bg-strong: oklch(22% 0.014 260 / 0.70);
    --glass-border: 1px solid oklch(100% 0 0 / 0.10);
    --glass-shadow: 0 2px 20px oklch(0% 0 0 / 0.3), 0 0.5px 0.5px oklch(0% 0 0 / 0.2);
    --glass-shadow-lg: 0 8px 40px oklch(0% 0 0 / 0.4), 0 2px 8px oklch(0% 0 0 / 0.25);
    --glass-shadow-xl: 0 16px 64px oklch(0% 0 0 / 0.5), 0 4px 16px oklch(0% 0 0 / 0.3);
    --glass-highlight: inset 0 1px 0 oklch(100% 0 0 / 0.08);
  }
}

/* ── Reset & base ───────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: 1.6;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  padding-top: env(safe-area-inset-top);
  padding-bottom: env(safe-area-inset-bottom);
}

/* Mesh gradient background */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(ellipse 80% 60% at 20% 10%, var(--bg-mesh-1) 0%, transparent 60%),
    radial-gradient(ellipse 60% 50% at 80% 20%, var(--bg-mesh-2) 0%, transparent 55%),
    radial-gradient(ellipse 70% 60% at 50% 90%, var(--bg-mesh-3) 0%, transparent 50%);
}

img, svg { display: block; max-width: 100%; }
a { color: var(--accent); text-decoration: none; transition: color 0.15s; }
a:hover { color: var(--accent-hover); }
button { font: inherit; cursor: pointer; touch-action: manipulation; }
p { text-wrap: pretty; }
h1, h2, h3, h4 { text-wrap: balance; font-family: var(--font-display); letter-spacing: -0.02em; }

/* ── Layout ─────────────────────────────────────────── */
.container {
  max-width: var(--container);
  margin-inline: auto;
  padding-left: max(var(--gutter), env(safe-area-inset-left));
  padding-right: max(var(--gutter), env(safe-area-inset-right));
}
.section {
  padding-block: clamp(48px, 8vw, var(--gap-2xl));
  position: relative;
  z-index: 1;
}
.stack { display: flex; flex-direction: column; }
.stack > * + * { margin-top: var(--gap-md); }
.row-between { display: flex; align-items: center; justify-content: space-between; gap: var(--gap-md); }

/* ── Typography ─────────────────────────────────────── */
h1 { font-size: var(--fs-h1); line-height: 1.1; font-weight: 700; margin: 0; letter-spacing: -0.03em; }
h2 { font-size: var(--fs-h2); line-height: 1.15; font-weight: 700; margin: 0; letter-spacing: -0.025em; }
h3 { font-size: var(--fs-h3); font-weight: 600; line-height: 1.3; margin: 0; }
.lead { font-size: var(--fs-lead); line-height: 1.6; color: var(--muted); max-width: 56ch; margin: 0; }
.eyebrow {
  font-family: var(--font-mono); font-size: var(--fs-xs); font-weight: 500;
  letter-spacing: 0.12em; text-transform: uppercase; color: var(--accent);
  margin: 0 0 var(--gap-sm);
}
.badge {
  display: inline-flex; align-items: center; gap: 6px;
  font-family: var(--font-mono); font-size: var(--fs-xs); font-weight: 500;
  letter-spacing: 0.04em; color: var(--accent);
  background: var(--accent-soft);
  padding: 5px 14px; border-radius: var(--radius-pill);
}

/* ══════════════════════════════════════════════════════
   TOP NAV — Frosted glass bar
   ══════════════════════════════════════════════════════ */
.topnav {
  position: sticky; top: 0; z-index: 20;
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-bottom: var(--glass-border);
  box-shadow: var(--glass-highlight);
}
.topnav-inner {
  display: flex; align-items: center; justify-content: space-between;
  padding-block: 12px;
  padding-left: max(var(--gutter), env(safe-area-inset-left));
  padding-right: max(var(--gutter), env(safe-area-inset-right));
}
.topnav .logo {
  display: flex; align-items: center; gap: 10px;
  font-family: var(--font-display); font-size: 16px; font-weight: 700;
  letter-spacing: -0.02em; color: var(--fg); text-decoration: none;
  transition: opacity 0.15s;
}
.topnav .logo:hover { opacity: 0.8; }
.topnav .logo em { font-style: normal; color: var(--accent); }
.logo-icon { width: 28px; height: 28px; flex-shrink: 0; }
.topnav nav { display: flex; gap: var(--gap-lg); }
.topnav nav a {
  font-size: 14px; font-weight: 500; color: var(--muted);
  transition: color 0.15s; letter-spacing: -0.01em;
}
.topnav nav a:hover { color: var(--fg); }
.topnav-actions { display: flex; align-items: center; gap: 6px; position: relative; }

/* Icon buttons */
.icon-btn, .menu-btn {
  display: grid; place-items: center;
  width: 34px; height: 34px;
  border-radius: var(--radius);
  border: var(--glass-border);
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  color: var(--muted);
  transition: all 0.2s;
  box-shadow: var(--glass-shadow);
}
.icon-btn:hover, .menu-btn:hover { color: var(--fg); border-color: var(--border-strong); background: var(--surface-hover); }
.icon-btn svg, .menu-btn svg, .icon-btn .icon-img, .menu-btn .icon-img { width: 16px; height: 16px; }
.icon-img { width: 16px; height: 16px; color: inherit; vertical-align: middle; }
.menu-btn { display: none; }

/* ══════════════════════════════════════════════════════
   LANGUAGE DROPDOWN
   ══════════════════════════════════════════════════════ */
.lang-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 160px;
  background: var(--glass-bg-strong);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius);
  box-shadow: var(--glass-shadow-lg);
  padding: 6px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-8px);
  transition: all 0.2s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  z-index: 100;
}
.lang-dropdown.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.lang-option {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 8px;
  color: var(--fg);
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: all 0.15s;
}
.lang-option:hover {
  background: var(--surface-hover);
  color: var(--accent);
}
.lang-option[aria-current="true"] {
  background: var(--accent-soft);
  color: var(--accent);
}
.lang-flag {
  font-size: 18px;
  line-height: 1;
}
.lang-name {
  white-space: nowrap;
}

/* ══════════════════════════════════════════════════════
   HERO
   ══════════════════════════════════════════════════════ */
.hero {
  padding-block: clamp(56px, 10vw, 100px) clamp(40px, 6vw, 64px);
  text-align: center;
  position: relative;
  overflow: hidden;
}
.hero .badge { margin-bottom: var(--gap-md); }
.hero h1 { margin-bottom: var(--gap-md); }
.hero h1 span { color: var(--accent); }
.hero .lead { margin: 0 auto var(--gap-lg); }
.hero-features {
  display: flex; align-items: center; justify-content: center;
  gap: var(--gap-lg); flex-wrap: wrap;
  margin-top: var(--gap-lg);
}
.hero-feat {
  display: flex; align-items: center; gap: 8px;
  font-size: var(--fs-sm); color: var(--muted);
}
.hero-feat svg { width: 18px; height: 18px; color: var(--success); flex-shrink: 0; }

/* ══════════════════════════════════════════════════════
   FORGE — The main workspace
   ══════════════════════════════════════════════════════ */
#forge {
  padding-block: clamp(48px, 8vw, 80px);
}
.forge-workspace {
  max-width: 780px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}
.forge-header {
  text-align: center;
  max-width: 48ch;
  margin: 0 auto var(--gap-xl);
}
.forge-header h2 { margin-bottom: var(--gap-sm); }

/* Glass panel wrapping the two slots */
.forge-panel {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--glass-shadow-xl), var(--glass-highlight);
  padding: var(--gap-xl) var(--gap-lg);
  position: relative;
  overflow: hidden;
}

/* Connector between two slots */
.forge-connector {
  display: flex;
  align-items: center;
  justify-content: center;
  margin: var(--gap-md) 0;
}
.forge-connector-icon {
  width: 40px; height: 40px;
  border-radius: 50%;
  background: var(--accent-soft);
  display: grid; place-items: center;
  color: var(--accent);
  font-size: 18px; font-weight: 600;
  flex-shrink: 0;
}
.forge-connector-line {
  flex: 1; height: 1px;
  background: linear-gradient(90deg, transparent, var(--border-strong), transparent);
}

/* Two-slot grid */
.forge-slots {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--gap-lg);
}
@media (max-width: 640px) {
  .forge-slots { grid-template-columns: 1fr; }
  .forge-connector { margin: var(--gap-sm) 0; }
  .book-container-epub {
    --book-width: 140px;
    --book-height: 196px;
  }
  .result-book .book-container {
    --book-width: 160px;
    --book-height: 224px;
  }
  .result-book-glow { width: 180px; }
}

/* ── Upload slot (glass card) ───────────────────────── */
.slot {
  position: relative;
  background: var(--surface);
  border: 1.5px dashed var(--border-strong);
  border-radius: var(--radius-lg);
  padding: 36px 20px 32px;
  text-align: center;
  transition: all 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  min-height: 280px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
  touch-action: manipulation;
  overflow: hidden;
}
.slot:hover, .slot.dragover {
  border-color: var(--accent);
  background: var(--surface-hover);
  box-shadow: 0 0 0 4px var(--accent-soft), var(--glass-shadow-lg);
  transform: translateY(-2px);
}
.slot[data-type="img"]:hover, .slot[data-type="img"].dragover {
  border-color: var(--purple);
  box-shadow: 0 0 0 4px var(--purple-soft), var(--glass-shadow-lg);
}
.slot.loaded {
  border-style: solid;
  border-color: var(--border-strong);
  padding: 16px;
  background: var(--glass-bg-strong);
  box-shadow: var(--glass-shadow-lg);
}
.slot.loaded[data-type="epub"] { border-color: var(--accent); }
.slot.loaded[data-type="img"] { border-color: var(--purple); }
.slot input[type="file"] { position: absolute; inset: 0; opacity: 0; cursor: pointer; z-index: 2; }
.slot.loaded input[type="file"] { cursor: pointer; }

/* Empty state */
.slot-icon { width: 52px; height: 52px; color: var(--muted-2); margin-bottom: 4px; }
.slot-label {
  font-family: var(--font-display);
  font-size: 15px; font-weight: 600;
  color: var(--fg); letter-spacing: -0.01em;
}
.slot-hint {
  font-family: var(--font-mono);
  font-size: var(--fs-xs); color: var(--muted-2);
  letter-spacing: 0.04em;
}
.slot.loaded .slot-icon,
.slot.loaded .slot-label,
.slot.loaded .slot-hint { display: none; }

/* ── Replace overlay (hover on loaded slot) ─────────── */
.slot-replace {
  display: none;
  position: absolute; inset: 0; z-index: 3;
  align-items: center; justify-content: center;
  background: oklch(0% 0 0 / 0.45);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
  border-radius: calc(var(--radius-lg) - 1px);
  opacity: 0;
  transition: opacity 0.25s;
  cursor: pointer;
}
.slot-replace-inner {
  display: flex; align-items: center; gap: 8px;
  padding: 10px 22px;
  background: oklch(100% 0 0 / 0.92);
  border-radius: var(--radius-pill);
  font-size: 14px; font-weight: 600;
  color: oklch(20% 0 0);
  box-shadow: 0 4px 16px oklch(0% 0 0 / 0.2);
}
.slot-replace-inner svg { width: 16px; height: 16px; }
.slot.loaded .slot-replace { display: flex; }
.slot.loaded:hover .slot-replace { opacity: 1; }

/* Slot check mark */
.slot-check {
  position: absolute; top: 10px; right: 10px;
  width: 22px; height: 22px;
  border-radius: 50%;
  background: var(--success);
  color: oklch(100% 0 0);
  display: none;
  place-items: center;
  font-size: 12px; font-weight: 700;
  z-index: 4;
  box-shadow: 0 2px 8px oklch(52% 0.17 155 / 0.3);
}
.slot.loaded .slot-check { display: grid; }

/* ── Book preview ───────────────────────────────────── */
.book-preview {
  display: none;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  width: 100%;
}
.slot.loaded .book-preview { display: flex; }

/* ── 2D Book ────────────────────────────────────────── */
.book-container {
  display: flex;
  justify-content: center;
}
.book-container-epub {
  --book-width: 160px;
  --book-height: 224px;
}
.book-container-result {
  --book-width: 220px;
  --book-height: 308px;
}
.book {
  width: var(--book-width);
  height: var(--book-height);
  position: relative;
  border-radius: 3px;
  overflow: hidden;
  box-shadow: 
    0 4px 6px rgba(0, 0, 0, 0.1),
    0 10px 20px rgba(0, 0, 0, 0.15),
    0 20px 40px rgba(0, 0, 0, 0.1);
  animation: book-enter 0.6s cubic-bezier(0.16, 1, 0.3, 1) both;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}
@keyframes book-enter {
  from { transform: translateY(20px) scale(0.95); opacity: 0; }
  to   { transform: translateY(0) scale(1); opacity: 1; }
}
.book:hover {
  transform: translateY(-5px) scale(1.02);
  box-shadow: 
    0 8px 12px rgba(0, 0, 0, 0.15),
    0 15px 30px rgba(0, 0, 0, 0.2),
    0 25px 50px rgba(0, 0, 0, 0.15);
}
.book-cover-front {
  width: 100%;
  height: 100%;
  position: relative;
}
.book-cover-front img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.book-cover-front::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg,
    rgba(255, 255, 255, 0.15) 0%,
    transparent 50%,
    rgba(0, 0, 0, 0.05) 100%);
  pointer-events: none;
}

/* 书脊效果 - 2D */
.book::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  width: 12px;
  height: 100%;
  background: linear-gradient(to right,
    rgba(0, 0, 0, 0.35) 0%,
    rgba(0, 0, 0, 0.15) 30%,
    rgba(255, 255, 255, 0.08) 45%,
    rgba(0, 0, 0, 0.05) 55%,
    transparent 100%);
  z-index: 1;
  pointer-events: none;
}

/* 书脊折痕线 */
.book::after {
  content: '';
  position: absolute;
  left: 8px;
  top: 0;
  width: 2px;
  height: 100%;
  background: linear-gradient(to bottom,
    transparent 0%,
    rgba(0, 0, 0, 0.15) 5%,
    rgba(0, 0, 0, 0.25) 15%,
    rgba(0, 0, 0, 0.3) 50%,
    rgba(0, 0, 0, 0.25) 85%,
    rgba(0, 0, 0, 0.15) 95%,
    transparent 100%);
  z-index: 2;
  pointer-events: none;
}

.book-filename {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--muted);
  word-break: break-all;
  max-width: 200px;
  text-align: center;
}

/* ── Picture frame preview (image slot loaded) ──────── */
.frame-preview {
  display: none;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  width: 100%;
}
.slot.loaded .frame-preview { display: flex; }

.frame-art {
  position: relative;
  background: oklch(100% 0 0);
  border-radius: 4px;
  padding: 10px;
  box-shadow:
    var(--glass-shadow-lg),
    inset 0 0 0 1px oklch(90% 0.01 260);
  max-width: 180px;
  max-height: 220px;
}
[data-theme="dark"] .frame-art {
  background: oklch(24% 0.01 260);
  box-shadow:
    var(--glass-shadow-lg),
    inset 0 0 0 1px oklch(30% 0.01 260);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .frame-art {
    background: oklch(24% 0.01 260);
    box-shadow:
      var(--glass-shadow-lg),
      inset 0 0 0 1px oklch(30% 0.01 260);
  }
}
.frame-art img {
  width: 100%; height: 100%;
  max-height: 190px;
  object-fit: cover;
  border-radius: 2px;
  display: block;
}
.frame-filename {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  color: var(--muted);
  word-break: break-all;
  max-width: 180px;
  text-align: center;
}

/* ── Forge actions ──────────────────────────────────── */
.forge-actions {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
  margin-top: var(--gap-lg);
}
.forge-btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 16px 48px;
  background: var(--accent);
  color: var(--on-accent);
  border: none;
  border-radius: var(--radius-pill);
  font-family: var(--font-display);
  font-size: 16px;
  font-weight: 600;
  letter-spacing: -0.01em;
  transition: all 0.25s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  box-shadow: 0 4px 16px oklch(57% 0.20 258 / 0.3);
  position: relative;
  overflow: hidden;
}
.forge-btn::before {
  content: '';
  position: absolute; inset: 0;
  background: linear-gradient(180deg, oklch(100% 0 0 / 0.15) 0%, transparent 50%);
  border-radius: inherit;
  pointer-events: none;
}
.forge-btn:hover:not(:disabled) {
  transform: translateY(-2px) scale(1.02);
  box-shadow: 0 8px 28px oklch(57% 0.20 258 / 0.4);
  background: var(--accent-hover);
}
.forge-btn:active:not(:disabled) { transform: translateY(0) scale(0.98); }
.forge-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  box-shadow: none;
}
.forge-btn svg { width: 18px; height: 18px; position: relative; z-index: 1; }
.forge-btn span { position: relative; z-index: 1; }
.forge-btn.loading {
  animation: btn-pulse 1.5s ease-in-out infinite;
}
@keyframes btn-pulse {
  0%, 100% { box-shadow: 0 4px 16px oklch(57% 0.20 258 / 0.3); }
  50% { box-shadow: 0 4px 32px oklch(57% 0.20 258 / 0.6); }
}

.forge-reset {
  font-family: var(--font-mono);
  font-size: var(--fs-sm);
  color: var(--muted);
  background: none;
  border: none;
  letter-spacing: 0.02em;
  transition: color 0.15s;
}
.forge-reset:hover { color: var(--fg); }

/* ══════════════════════════════════════════════════════
   RESULT — Book with new cover + download
   ══════════════════════════════════════════════════════ */
.result {
  display: none;
  flex-direction: column;
  align-items: center;
  gap: 20px;
  text-align: center;
  padding: var(--gap-xl) 0;
}
.result.show { display: flex; }

.result-glass {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--glass-shadow-xl), var(--glass-highlight);
  padding: var(--gap-xl) var(--gap-lg);
  max-width: 420px;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
}
.result-badge {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: var(--fs-xs); font-weight: 600;
  letter-spacing: 0.04em; text-transform: uppercase;
  color: var(--success);
  background: var(--success-soft);
  padding: 5px 14px; border-radius: var(--radius-pill);
}
.result-badge svg { width: 14px; height: 14px; }

/* ── Result Book — 2D ───────────────────────────────── */
.result-book {
  display: flex;
  justify-content: center;
}
.result-book .book-container {
  --book-width: 220px;
  --book-height: 308px;
}
.result-book .book {
  animation: result-enter 0.6s cubic-bezier(0.16, 1, 0.3, 1) both;
}
@keyframes result-enter {
  from { transform: translateY(30px) scale(0.9); opacity: 0; }
  to   { transform: translateY(0) scale(1); opacity: 1; }
}
.result-book .book:hover {
  transform: translateY(-8px) scale(1.03);
}


/* Success glow under book */
.result-book-glow {
  width: 260px; height: 60px;
  background: radial-gradient(ellipse, var(--accent) 0%, transparent 70%);
  opacity: 0.18;
  filter: blur(16px);
  margin-top: -24px;
  animation: glow-pulse 3s ease-in-out infinite;
}
@keyframes glow-pulse {
  0%, 100% { opacity: 0.14; transform: scale(1); }
  50% { opacity: 0.26; transform: scale(1.06); }
}

.result-title {
  font-family: var(--font-display);
  font-size: 22px; font-weight: 700;
  letter-spacing: -0.02em;
}
.result-meta {
  font-family: var(--font-mono);
  font-size: var(--fs-sm);
  color: var(--muted);
}

.dl-btn {
  display: inline-flex;
  align-items: center; gap: 8px;
  padding: 14px 36px;
  background: var(--success);
  color: oklch(100% 0 0);
  border: none;
  border-radius: var(--radius-pill);
  font-family: var(--font-display);
  font-size: 15px; font-weight: 600;
  letter-spacing: -0.01em;
  transition: all 0.2s;
  box-shadow: 0 4px 16px oklch(52% 0.17 155 / 0.3);
}
.dl-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 28px oklch(52% 0.17 155 / 0.45);
}
.dl-btn svg { width: 16px; height: 16px; }

.btn-outline {
  display: inline-flex;
  align-items: center; gap: 8px;
  padding: 12px 28px;
  background: transparent;
  color: var(--accent);
  border: 1.5px solid var(--accent);
  border-radius: var(--radius-pill);
  font-family: var(--font-display);
  font-size: 14px; font-weight: 600;
  letter-spacing: -0.01em;
  transition: all 0.2s;
}
.btn-outline:hover {
  background: var(--accent);
  color: var(--on-accent);
  transform: translateY(-1px);
}

/* ══════════════════════════════════════════════════════
   DEVICES
   ══════════════════════════════════════════════════════ */
.dev-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}
@media (max-width: 920px) { .dev-grid { grid-template-columns: 1fr; } }
.dev-card {
  position: relative;
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius-lg);
  padding: 28px 22px 24px;
  transition: all 0.25s;
  box-shadow: var(--glass-shadow), var(--glass-highlight);
}
.dev-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--glass-shadow-lg), var(--glass-highlight);
  border-color: var(--accent);
}
.dev-card-badge {
  position: absolute;
  top: 12px; right: 14px;
  font-family: var(--font-mono); font-size: 10px;
  letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 3px 10px; border-radius: var(--radius-pill);
}
.dev-card-icon {
  width: 42px; height: 42px;
  display: grid; place-items: center;
  margin-bottom: 16px;
  border: var(--glass-border);
  border-radius: var(--radius);
  color: var(--accent);
  background: var(--accent-soft);
  box-shadow: var(--glass-shadow);
}
.dev-card-icon svg { width: 20px; height: 20px; }
.dev-card h3 {
  font-size: 17px; font-weight: 600;
  letter-spacing: -0.015em;
  margin-bottom: 8px;
}
.dev-card p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.6; }

/* ══════════════════════════════════════════════════════
   HOW IT WORKS
   ══════════════════════════════════════════════════════ */
.how-steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}
@media (max-width: 920px) { .how-steps { grid-template-columns: 1fr; } }
.step-card {
  position: relative;
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius-lg);
  padding: 32px 22px 24px;
  box-shadow: var(--glass-shadow), var(--glass-highlight);
  transition: all 0.25s;
  overflow: hidden;
}
.step-card:hover { transform: translateY(-2px); border-color: var(--accent); }
.step-card::before {
  position: absolute;
  top: 14px; left: 18px;
  width: 28px; height: 28px;
  display: grid; place-items: center;
  background: var(--accent);
  border-radius: 50%;
  font-family: var(--font-display);
  font-size: 13px; font-weight: 700;
  color: var(--on-accent);
}
.step-card:nth-child(1)::before { content: '1'; }
.step-card:nth-child(2)::before { content: '2'; }
.step-card:nth-child(3)::before { content: '3'; }
.step-card h3 {
  margin-top: 24px;
  margin-bottom: 8px;
  font-family: var(--font-display);
  font-size: 17px; font-weight: 600;
}
.step-card p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.6; }

/* ══════════════════════════════════════════════════════
   FAQ
   ══════════════════════════════════════════════════════ */
.faq-list { max-width: 680px; margin: 0 auto; }
.faq-item {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius);
  margin-bottom: 8px;
  box-shadow: var(--glass-shadow), var(--glass-highlight);
  overflow: hidden;
}
.faq-q {
  display: flex; align-items: center; justify-content: space-between; gap: var(--gap-md);
  width: 100%; padding: 16px 20px;
  background: none; border: none;
  font-family: var(--font-display);
  font-size: 15px; font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--fg); text-align: left;
  transition: color 0.15s;
  list-style: none;
}
.faq-q::-webkit-details-marker { display: none; }
.faq-q:hover { color: var(--accent); }
.faq-q svg {
  width: 16px; height: 16px; flex-shrink: 0;
  color: var(--muted-2); transition: transform 0.2s;
}
.faq-item[open] .faq-q svg { transform: rotate(45deg); }
.faq-a {
  padding: 0 20px 16px;
  color: var(--muted); font-size: 14px; line-height: 1.65;
  max-width: 60ch;
}

/* ══════════════════════════════════════════════════════
   CTA
   ══════════════════════════════════════════════════════ */
.cta-strip {
  text-align: center;
  padding-block: clamp(56px, 9vw, 100px);
}
.cta-glass {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--glass-shadow-xl), var(--glass-highlight);
  padding: var(--gap-xl) var(--gap-lg);
  max-width: 560px;
  margin: 0 auto;
}
.cta-glass h2 { margin-bottom: var(--gap-sm); }
.cta-glass .lead { margin: 0 auto var(--gap-lg); }

/* ══════════════════════════════════════════════════════
   FOOTER
   ══════════════════════════════════════════════════════ */
.pagefoot {
  padding-block: var(--gap-xl);
  padding-left: max(var(--gutter), env(safe-area-inset-left));
  padding-right: max(var(--gutter), env(safe-area-inset-right));
  color: var(--muted);
  font-size: var(--fs-sm);
  border-top: var(--glass-border);
  position: relative;
  z-index: 1;
}
.pagefoot .row-between { flex-wrap: wrap; gap: var(--gap-md); }

/* ══════════════════════════════════════════════════════
   CANVAS (particles only)
   ══════════════════════════════════════════════════════ */
#ambientCanvas { display: none; }
#particles {
  position: fixed; inset: 0; z-index: 100;
  pointer-events: none;
  display: none;
}
#particles.active { display: block; }

/* ── Accessibility ──────────────────────────────────── */
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0,0,0,0); border: 0;
}
:focus { outline: none; }
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 6px;
}
.forge-btn:focus-visible, .dl-btn:focus-visible, .btn-outline:focus-visible {
  outline-offset: 4px;
  box-shadow: 0 0 0 4px var(--accent-soft);
}
.slot:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
  border-color: var(--accent);
}
details summary:focus-visible { outline-offset: 4px; }

/* ── Mobile hamburger ───────────────────────────────── */
@media (max-width: 640px) {
  :root { --gutter: 16px; }
  .menu-btn { display: grid; }
  .topnav nav {
    display: none;
    position: absolute;
    top: 100%; left: 0; right: 0;
    background: var(--glass-bg-strong);
    backdrop-filter: var(--glass-blur);
    -webkit-backdrop-filter: var(--glass-blur);
    border-bottom: var(--glass-border);
    flex-direction: column;
    padding: 8px max(var(--gutter), env(safe-area-inset-left)) 16px;
    gap: 0;
    box-shadow: var(--glass-shadow-xl);
  }
  .topnav nav.open { display: flex; }
  .topnav nav a {
    padding: 14px 0;
    border-bottom: 1px solid var(--border);
    font-size: 15px;
  }
  .topnav nav a:last-child { border-bottom: none; }
  .topnav-inner { position: relative; }
}

/* ── Mobile: always-visible replace hint ───────────── */
@media (hover: none) and (pointer: coarse) {
  .slot.loaded .slot-replace {
    display: flex;
    opacity: 1;
    background: linear-gradient(to top, oklch(0% 0 0 / 0.55) 0%, oklch(0% 0 0 / 0.2) 60%, transparent 100%);
    backdrop-filter: none;
    -webkit-backdrop-filter: none;
    align-items: flex-end;
    padding-bottom: 12px;
  }
  .slot-replace-inner {
    padding: 8px 18px;
    font-size: 12px;
    background: oklch(100% 0 0 / 0.85);
    box-shadow: 0 2px 10px oklch(0% 0 0 / 0.15);
  }
  .slot.loaded {
    padding-bottom: 52px;
  }
}

/* ── Animations ─────────────────────────────────────── */
@keyframes fade-in-up {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}
.result.show {
  animation: fade-in-up 0.5s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

/* ══════════════════════════════════════════════════════
   SHARE SECTION
   ══════════════════════════════════════════════════════ */
.share-strip {
  text-align: center;
  max-width: 560px;
  margin: 0 auto;
}
.share-btns {
  display: flex; align-items: center; justify-content: center;
  gap: 10px; flex-wrap: wrap;
}
.share-btn {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 10px 18px;
  border-radius: var(--radius-pill);
  font-size: var(--fs-sm); font-weight: 600;
  border: 1px solid var(--border-strong);
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  color: var(--fg);
  text-decoration: none;
  transition: all 0.2s;
  box-shadow: var(--glass-shadow);
  cursor: pointer;
}
.share-btn svg { width: 16px; height: 16px; flex-shrink: 0; }
.share-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--glass-shadow-lg);
  color: var(--fg);
}
.share-x:hover { border-color: oklch(45% 0.02 0); background: oklch(20% 0.02 0); color: oklch(100% 0 0); }
.share-fb:hover { border-color: oklch(50% 0.18 260); background: oklch(50% 0.18 260); color: oklch(100% 0 0); }
.share-reddit:hover { border-color: oklch(58% 0.20 25); background: oklch(58% 0.20 25); color: oklch(100% 0 0); }
.share-li:hover { border-color: oklch(50% 0.14 260); background: oklch(50% 0.14 260); color: oklch(100% 0 0); }
.share-copy:hover { border-color: var(--accent); color: var(--accent); }
.share-copy.copied { border-color: var(--success); color: var(--success); }

@media (max-width: 640px) {
  .share-btns { gap: 8px; }
  .share-btn { padding: 9px 14px; font-size: 12px; }
  .share-btn span { display: none; }
  .share-btn svg { width: 18px; height: 18px; }
}

/* ══════════════════════════════════════════════════════
   FOOTER — Two-column grid
   ══════════════════════════════════════════════════════ */
.foot-grid {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--gap-xl);
  flex-wrap: wrap;
}
.foot-brand { flex: 1 1 300px; }
.foot-links {
  display: flex; align-items: center; gap: var(--gap-lg);
  flex-wrap: wrap;
}
.foot-links a {
  font-size: var(--fs-sm); color: var(--muted);
  transition: color 0.15s; text-decoration: none;
}
.foot-links a:hover { color: var(--fg); }
.foot-feedback-btn {
  font-size: var(--fs-sm); color: var(--accent);
  background: none; border: none; padding: 0;
  font-weight: 500; cursor: pointer;
  transition: color 0.15s;
}
.foot-feedback-btn:hover { color: var(--accent-hover); text-decoration: underline; }

/* ══════════════════════════════════════════════════════
   FEEDBACK MODAL
   ══════════════════════════════════════════════════════ */
.feedback-overlay {
  position: fixed; inset: 0; z-index: 50;
  background: oklch(0% 0 0 / 0.45);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: none;
  align-items: center; justify-content: center;
  padding: var(--gutter);
}
.feedback-overlay.open { display: flex; }
.feedback-modal {
  background: var(--surface-solid);
  border: var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--glass-shadow-xl);
  width: 100%; max-width: 460px;
  position: relative;
  animation: fade-in-up 0.3s ease;
}
.feedback-modal-lark {
  max-width: 680px;
  max-height: 90vh;
  display: flex;
  flex-direction: column;
}
.feedback-lark-container {
  flex: 1;
  min-height: 720px;
  overflow: hidden;
  border-radius: var(--radius);
  position: relative;
}
.feedback-header-mask {
  position: absolute;
  top: 0;
  right: 0;
  width: 100%;
  height: 60px;
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: var(--glass-border);
  border-top: none;
  border-right: none;
  z-index: 5;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding-right: 12px;
}
.feedback-close-btn {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  border: none;
  background: var(--surface-hover);
  color: var(--muted);
  cursor: pointer;
  display: grid;
  place-items: center;
  transition: all 0.2s;
  font-size: 18px;
  line-height: 1;
}
.feedback-close-btn:hover {
  background: var(--accent-soft);
  color: var(--accent);
  transform: scale(1.1);
}
.feedback-loading {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 20px;
  background: var(--surface-solid);
  z-index: 10;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}
.feedback-loading.hidden {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}
.feedback-spinner {
  position: relative;
  width: 60px;
  height: 60px;
}
.feedback-spinner-ring {
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  border: 3px solid transparent;
  animation: feedback-spin 1.5s linear infinite;
}
.feedback-spinner-ring:nth-child(1) {
  border-top-color: var(--accent);
  animation-delay: 0s;
}
.feedback-spinner-ring:nth-child(2) {
  border-right-color: var(--accent-hover, #1558d6);
  animation-delay: 0.15s;
  width: 80%;
  height: 80%;
  top: 10%;
  left: 10%;
}
.feedback-spinner-ring:nth-child(3) {
  border-bottom-color: var(--accent-soft, rgba(26, 109, 255, 0.2));
  animation-delay: 0.3s;
  width: 60%;
  height: 60%;
  top: 20%;
  left: 20%;
}
@keyframes feedback-spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}
.feedback-loading-text {
  font-size: var(--fs-body);
  color: var(--muted);
  font-weight: 500;
  letter-spacing: 0.5px;
}
.feedback-lark-iframe {
  width: 100%;
  height: 100%;
  min-height: 720px;
  border: none;
  border-radius: var(--radius);
}
.feedback-form { display: flex; flex-direction: column; gap: var(--gap-md); }
.feedback-label {
  display: flex; flex-direction: column; gap: 6px;
  font-size: var(--fs-sm); font-weight: 500; color: var(--muted);
}
.feedback-label select,
.feedback-label textarea,
.feedback-label input {
  font: inherit; font-size: var(--fs-body);
  padding: 10px 14px;
  border-radius: var(--radius);
  border: 1px solid var(--border-strong);
  background: var(--surface);
  color: var(--fg);
  transition: border-color 0.15s;
  resize: vertical;
}
.feedback-label select:focus,
.feedback-label textarea:focus,
.feedback-label input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.feedback-submit {
  padding: 12px 24px;
  border-radius: var(--radius-pill);
  border: none;
  background: var(--accent);
  color: var(--on-accent);
  font-weight: 600; font-size: var(--fs-body);
  cursor: pointer; transition: all 0.2s;
}
.feedback-submit:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px oklch(57% 0.20 258 / 0.3);
}
.feedback-thanks {
  display: flex; flex-direction: column;
  align-items: center; gap: 12px;
  padding: var(--gap-lg) 0;
  text-align: center;
}
.feedback-thanks svg { width: 40px; height: 40px; }
.feedback-thanks p { margin: 0; font-size: var(--fs-lead); color: var(--fg); }