/* =========================================================
   OpenAI Book Recommender – "Old Library" theme
   All colours live here. Change the palette in one minute.
   ========================================================= */

:root {
  /* Brand palette (the original colours) */
  --brand-rose: #703b3b;   /* rgb(112, 59, 59)   */
  --brand-sand: #e1d0b3;   /* rgb(225, 208, 179) */
  --brand-sky: #9bb4c0;    /* rgb(155, 180, 192) */
  --brand-oak: #a18d6d;    /* rgb(161, 141, 109) */

  /* Light theme – warm paper */
  --bg: #f5eee2;
  --bg-deep: var(--brand-sand);
  --surface: #fcf8f1;
  --text: #2e1e1e;
  --text-muted: #5b4a33;
  --heading: var(--brand-rose);
  --accent: var(--brand-rose);
  --accent-hover: #5c2f2f;
  --on-accent: #ffffff;
  --accent-2: var(--brand-sky);
  --accent-2-text: #3d5c6b;
  --line: var(--brand-oak);
  --shelf-wood: #8a7658;
  --focus: #2f5a6e;
  --shadow: rgb(112 59 59 / 0.18);
  --shadow-strong: rgb(112 59 59 / 0.3);
  --ripple: rgb(255 255 255 / 0.45);
  --spine-shade: rgb(0 0 0 / 0.14);
  --spine-shine: rgb(255 255 255 / 0.14);

  /* Book spine colours (cards cycle through them) */
  --spine-0: var(--brand-rose);
  --spine-1: var(--brand-sky);
  --spine-2: var(--brand-oak);
  --spine-3: #8c5a4a;

  /* Shape & type */
  --font: "Nunito", system-ui, -apple-system, "Segoe UI", sans-serif;
  --radius-sm: 6px;
  --radius: 14px;
  --radius-pill: 999px;
  --ease-bounce: cubic-bezier(0.34, 1.56, 0.64, 1);
  --ease-out: cubic-bezier(0.22, 1, 0.36, 1);
}

/* Dark theme – a library at night: coffee-brown wood, never pure black */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #1d1614;
    --bg-deep: #2a1f1b;
    --surface: #2b211d;
    --text: #f2e8d8;
    --text-muted: #cbb99a;
    --heading: #e1d0b3;
    --accent: #d9a3a3;
    --accent-hover: #e8bdbd;
    --on-accent: #2a1414;
    --accent-2-text: #b3cad4;
    --shelf-wood: #6e5d45;
    --focus: #b3cad4;
    --shadow: rgb(0 0 0 / 0.35);
    --shadow-strong: rgb(0 0 0 / 0.55);
    --ripple: rgb(112 59 59 / 0.35);
    --spine-3: #c08a78;
  }
}

:root[data-theme="dark"] {
  --bg: #1d1614;
  --bg-deep: #2a1f1b;
  --surface: #2b211d;
  --text: #f2e8d8;
  --text-muted: #cbb99a;
  --heading: #e1d0b3;
  --accent: #d9a3a3;
  --accent-hover: #e8bdbd;
  --on-accent: #2a1414;
  --accent-2-text: #b3cad4;
  --shelf-wood: #6e5d45;
  --focus: #b3cad4;
  --shadow: rgb(0 0 0 / 0.35);
  --shadow-strong: rgb(0 0 0 / 0.55);
  --ripple: rgb(112 59 59 / 0.35);
  --spine-3: #c08a78;
}

/* ---------- Base ---------- */

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

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font);
  font-size: 1.0625rem;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--bg);
  /* Faint ruled-paper lines */
  background-image: repeating-linear-gradient(
    to bottom,
    transparent 0 31px,
    color-mix(in srgb, var(--line) 14%, transparent) 31px 32px
  );
  overflow-x: hidden;
  transition: background-color 0.4s ease, color 0.4s ease;
}

h1,
h2,
h3 {
  color: var(--heading);
  line-height: 1.15;
  margin: 0;
}

a {
  color: var(--accent);
  text-underline-offset: 3px;
}

a:hover {
  color: var(--accent-hover);
}

:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

main:focus {
  outline: none;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: 1rem;
  z-index: 100;
  padding: 0.6rem 1rem;
  font-weight: 800;
  color: var(--on-accent);
  background: var(--accent);
  border-radius: var(--radius-sm);
  transform: translateY(-200%);
  transition: transform 0.2s ease;
}

.skip-link:focus {
  transform: translateY(0);
  color: var(--on-accent);
}

/* ---------- Living background ---------- */

.library-bg {
  position: fixed;
  inset: 0;
  z-index: -1;
  overflow: hidden;
  pointer-events: none;
}

.drift-book {
  position: absolute;
  bottom: -30vh;
  width: 26px;
  height: 120px;
  border-radius: 4px 4px 2px 2px;
  background: var(--spine-0);
  opacity: 0;
  box-shadow: inset -6px 0 0 var(--spine-shade), inset 0 14px 0 var(--spine-shine);
  animation: drift 26s linear infinite;
}

.drift-book:nth-child(1) { left: 4%;  animation-delay: 0s;   }
.drift-book:nth-child(2) { left: 15%; animation-delay: -6s;  height: 90px;  background: var(--spine-1); }
.drift-book:nth-child(3) { left: 27%; animation-delay: -14s; width: 20px;   background: var(--spine-2); }
.drift-book:nth-child(4) { left: 42%; animation-delay: -3s;  height: 140px; background: var(--spine-3); animation-duration: 32s; }
.drift-book:nth-child(5) { left: 56%; animation-delay: -19s; background: var(--spine-1); }
.drift-book:nth-child(6) { left: 68%; animation-delay: -9s;  height: 100px; width: 30px; }
.drift-book:nth-child(7) { left: 79%; animation-delay: -23s; background: var(--spine-2); animation-duration: 30s; }
.drift-book:nth-child(8) { left: 89%; animation-delay: -12s; height: 80px;  background: var(--spine-3); }
.drift-book:nth-child(9) { left: 96%; animation-delay: -17s; width: 18px;   background: var(--spine-1); }

@keyframes drift {
  0%   { transform: translateY(0) rotate(-8deg);      opacity: 0; }
  10%  { opacity: 0.16; }
  50%  { transform: translateY(-75vh) rotate(10deg);  }
  90%  { opacity: 0.16; }
  100% { transform: translateY(-150vh) rotate(-6deg); opacity: 0; }
}

/* ---------- Top bar ---------- */

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  max-width: 1120px;
  margin: 0 auto;
  padding: 1.25rem 1.25rem 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 900;
  font-size: 1.1rem;
  color: var(--heading);
  text-decoration: none;
}

.brand__icon {
  width: 32px;
  height: 32px;
}

.brand__icon rect:nth-child(1) { fill: var(--spine-0); }
.brand__icon rect:nth-child(2) { fill: var(--spine-1); }
.brand__icon rect:nth-child(3) { fill: var(--spine-2); }

.topbar__right {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.mode-badge {
  padding: 0.25rem 0.75rem;
  font-size: 0.85rem;
  font-weight: 800;
  color: var(--accent-2-text);
  border: 2px solid currentColor;
  border-radius: var(--radius-pill);
  white-space: nowrap;
}

.mode-badge[data-mode="live"] {
  color: var(--accent);
}

.theme-toggle {
  position: relative;
  overflow: hidden;
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  padding: 0;
  color: var(--heading);
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: 50%;
  cursor: pointer;
  box-shadow: 0 3px 0 var(--line);
  transition: transform 0.2s var(--ease-bounce), box-shadow 0.2s ease;
}

.theme-toggle:hover {
  transform: translateY(-2px) rotate(-8deg);
  box-shadow: 0 5px 0 var(--line);
}

.theme-toggle:active {
  transform: translateY(2px);
  box-shadow: 0 1px 0 var(--line);
}

.theme-toggle svg {
  grid-area: 1 / 1;
  width: 22px;
  height: 22px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  transition: transform 0.45s var(--ease-bounce), opacity 0.3s ease;
}

.theme-toggle__moon {
  fill: currentColor;
  opacity: 0;
  transform: rotate(-90deg) scale(0.4);
}

:root[data-theme="dark"] .theme-toggle__sun {
  opacity: 0;
  transform: rotate(90deg) scale(0.4);
}

:root[data-theme="dark"] .theme-toggle__moon {
  opacity: 1;
  transform: none;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .theme-toggle__sun {
    opacity: 0;
    transform: rotate(90deg) scale(0.4);
  }

  :root:not([data-theme="light"]) .theme-toggle__moon {
    opacity: 1;
    transform: none;
  }
}

/* ---------- Hero ---------- */

main {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

.hero {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  align-items: center;
  gap: 3rem;
  padding: 4rem 0 3rem;
}

.kicker {
  display: inline-block;
  margin: 0 0 0.75rem;
  padding: 0.2rem 0.8rem;
  font-weight: 800;
  font-size: 0.85rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-2-text);
  background: color-mix(in srgb, var(--accent-2) 22%, transparent);
  border-radius: var(--radius-pill);
}

h1 {
  font-size: clamp(2.4rem, 6vw, 4rem);
  font-weight: 900;
  letter-spacing: -0.02em;
}

.lead {
  max-width: 34rem;
  margin: 1rem 0 2rem;
  font-size: 1.15rem;
  color: var(--text-muted);
}

/* ---------- Form ---------- */

.picker {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: 1rem;
  padding: 1.25rem;
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius);
  box-shadow: 6px 6px 0 color-mix(in srgb, var(--line) 45%, transparent);
}

.field {
  display: grid;
  gap: 0.3rem;
  flex: 1 1 140px;
}

.field label {
  font-weight: 800;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.field select {
  width: 100%;
  min-height: 46px;
  padding: 0.5rem 2.25rem 0.5rem 0.75rem;
  font: inherit;
  font-weight: 600;
  color: var(--text);
  background-color: var(--bg);
  background-image:
    linear-gradient(45deg, transparent 50%, var(--accent) 50%),
    linear-gradient(135deg, var(--accent) 50%, transparent 50%);
  background-position: calc(100% - 18px) 50%, calc(100% - 12px) 50%;
  background-size: 6px 6px;
  background-repeat: no-repeat;
  border: 2px solid var(--line);
  border-radius: var(--radius-sm);
  appearance: none;
  cursor: pointer;
}

/* ---------- Buttons ---------- */

.btn {
  position: relative;
  overflow: hidden;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  min-height: 48px;
  padding: 0.7rem 1.4rem;
  white-space: nowrap;
  font: inherit;
  font-weight: 800;
  border: 0;
  border-radius: var(--radius-sm) var(--radius) var(--radius) var(--radius-sm);
  cursor: pointer;
  transition: transform 0.2s var(--ease-bounce), box-shadow 0.2s ease, background-color 0.2s ease;
}

.btn--primary {
  flex: 1 1 200px;
  color: var(--on-accent);
  background: var(--accent);
  box-shadow: 0 5px 0 var(--accent-hover), 0 10px 20px var(--shadow);
}

.btn--primary:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 0 var(--accent-hover), 0 16px 26px var(--shadow-strong);
}

.btn--primary:active {
  transform: translateY(4px);
  box-shadow: 0 1px 0 var(--accent-hover), 0 4px 8px var(--shadow);
}

.btn:disabled {
  cursor: progress;
  opacity: 0.75;
}

/* Book icon: the right page flips open on hover */
.btn__book {
  width: 24px;
  height: 24px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linejoin: round;
  overflow: visible;
}

.btn__book-page {
  transform-origin: 12px 12px;
  transition: transform 0.5s var(--ease-out);
}

.btn:hover .btn__book-page,
.btn:disabled .btn__book-page {
  transform: scaleX(-1);
}

.btn:disabled .btn__book-page {
  animation: page-flip 0.8s ease-in-out infinite alternate;
}

@keyframes page-flip {
  from { transform: scaleX(1); }
  to   { transform: scaleX(-1); }
}

.ripple {
  position: absolute;
  border-radius: 50%;
  background: var(--ripple);
  pointer-events: none;
  transform: scale(0);
  animation: ripple 0.6s ease-out forwards;
}

@keyframes ripple {
  to { transform: scale(1); opacity: 0; }
}

/* ---------- Decorative shelf ---------- */

.hero__shelf {
  justify-self: center;
  width: min(100%, 360px);
}

.shelf {
  display: flex;
  align-items: flex-end;
  justify-content: center;
  gap: 6px;
  height: 240px;
  padding: 0 1rem;
}

.spine {
  display: block;
  width: 38px;
  height: calc(var(--h) * var(--shelf-scale, 1) * 1px);
  border-radius: 5px 5px 2px 2px;
  box-shadow: inset -7px 0 0 var(--spine-shade), inset 0 18px 0 var(--spine-shine), 0 6px 14px var(--shadow);
  transform-origin: bottom center;
  animation: sway 6s ease-in-out infinite alternate;
}

/* A little golden band on each spine */
.spine::after {
  content: "";
  display: block;
  height: 5px;
  margin-top: 36px;
  background: color-mix(in srgb, var(--brand-sand) 70%, transparent);
}

.spine--1 { --h: 190; background: var(--spine-0); }
.spine--2 { --h: 160; background: var(--spine-1); width: 30px; animation-delay: -1s; }
.spine--3 { --h: 215; background: var(--spine-2); width: 44px; animation-delay: -2s; }
.spine--4 { --h: 175; background: var(--spine-3); animation-delay: -3s; }
.spine--5 { --h: 200; background: var(--spine-0); width: 32px; animation-delay: -4s; }
.spine--6 { --h: 150; background: var(--spine-1); animation-delay: -5s; }
.spine--7 { --h: 170; background: var(--spine-2); width: 34px; transform: rotate(14deg); animation: lean 6s ease-in-out infinite alternate; }

@keyframes sway {
  from { transform: rotate(-1.2deg); }
  to   { transform: rotate(1.2deg); }
}

@keyframes lean {
  from { transform: rotate(12deg); }
  to   { transform: rotate(16deg); }
}

.shelf__board {
  height: 18px;
  background: var(--shelf-wood);
  border-radius: 4px;
  box-shadow: 0 10px 0 color-mix(in srgb, var(--shelf-wood) 55%, transparent), 0 20px 30px var(--shadow);
}

/* ---------- Stats ---------- */

.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-bottom: 3rem;
}

.stat {
  display: grid;
  padding: 1rem 1.25rem;
  background: var(--surface);
  border-left: 6px solid var(--accent-2);
  border-radius: var(--radius-sm);
  box-shadow: 0 6px 16px var(--shadow);
}

.stat:nth-child(2) { border-left-color: var(--line); }
.stat:nth-child(3) { border-left-color: var(--accent); }

.stat__number {
  font-size: clamp(1.8rem, 5vw, 2.5rem);
  font-weight: 900;
  color: var(--heading);
  font-variant-numeric: tabular-nums;
}

.stat__label {
  font-weight: 600;
  color: var(--text-muted);
}

/* ---------- Results ---------- */

.results {
  padding-bottom: 4rem;
}

.results__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.5rem 1.5rem;
  margin-bottom: 1.5rem;
}

.results h2 {
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  font-weight: 900;
}

.status {
  margin: 0;
  font-weight: 600;
  color: var(--text-muted);
}

.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.5rem;
}

/* Empty shelf message (live mode, before the first request) */
.book-grid:empty::before {
  content: "Your shelf is empty – pick a genre above and press the button.";
  grid-column: 1 / -1;
  padding: 2.5rem 1.5rem;
  text-align: center;
  font-weight: 600;
  color: var(--text-muted);
  border: 2px dashed var(--line);
  border-radius: var(--radius);
}

/* A card that looks like a book cover lying on the desk */
.book {
  position: relative;
  display: flex;
  min-height: 220px;
  background: var(--surface);
  border-radius: 4px var(--radius) var(--radius) 4px;
  box-shadow:
    4px 4px 0 color-mix(in srgb, var(--line) 35%, transparent),
    8px 8px 0 color-mix(in srgb, var(--line) 18%, transparent),
    0 12px 24px var(--shadow);
  transition: transform 0.35s var(--ease-bounce), box-shadow 0.35s ease;
}

.book:hover {
  transform: translateY(-6px) rotate(-1deg);
  box-shadow:
    4px 4px 0 color-mix(in srgb, var(--line) 35%, transparent),
    8px 8px 0 color-mix(in srgb, var(--line) 18%, transparent),
    0 22px 36px var(--shadow-strong);
}

.book__spine {
  flex: 0 0 22px;
  background: var(--spine-0);
  border-radius: 4px 0 0 4px;
  box-shadow: inset -5px 0 0 var(--spine-shade);
}

.book[data-spine="1"] .book__spine { background: var(--spine-1); }
.book[data-spine="2"] .book__spine { background: var(--spine-2); }
.book[data-spine="3"] .book__spine { background: var(--spine-3); }

.book__body {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  padding: 1.25rem 1.25rem 1rem;
  width: 100%;
}

.book__genre {
  margin: 0;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-2-text);
}

.book__title {
  font-size: 1.3rem;
  font-weight: 800;
}

.book__author {
  margin: 0;
  font-style: italic;
  color: var(--text-muted);
}

.book__why {
  margin: 0.4rem 0 0;
  flex: 1;
}

.book__year {
  align-self: flex-end;
  margin: 0.5rem 0 0;
  padding: 0.1rem 0.7rem;
  font-weight: 800;
  font-size: 0.9rem;
  color: var(--heading);
  border: 2px solid var(--line);
  border-radius: var(--radius-pill);
}

.book__year:empty {
  display: none;
}

/* Loading placeholders with a moving shine */
.book--loading {
  overflow: hidden;
}

.book--loading::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(100deg, transparent 20%, color-mix(in srgb, var(--brand-sand) 45%, transparent) 50%, transparent 80%);
  transform: translateX(-100%);
  animation: shine 1.2s ease-in-out infinite;
}

@keyframes shine {
  to { transform: translateX(100%); }
}

/* ---------- Scroll reveal (only when JS is on) ---------- */

.js .reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out);
  transition-delay: calc(var(--i, 0) * 70ms);
}

.js .reveal.is-visible {
  opacity: 1;
  transform: none;
}

/* Keep the card hover snappy after it has appeared */
.js .book.reveal.is-visible {
  transition: transform 0.35s var(--ease-bounce), box-shadow 0.35s ease, opacity 0.6s var(--ease-out);
  transition-delay: 0s;
}

/* ---------- Footer ---------- */

.footer {
  padding: 2rem 1.25rem 2.5rem;
  text-align: center;
  font-weight: 600;
  color: var(--text-muted);
  border-top: 2px dashed color-mix(in srgb, var(--line) 50%, transparent);
}

.footer p {
  margin: 0;
}

/* ---------- Responsive ---------- */

@media (max-width: 820px) {
  .hero {
    grid-template-columns: 1fr;
    gap: 2rem;
    padding-top: 2.5rem;
  }

  .hero__shelf {
    order: -1;
    width: min(100%, 280px);
  }

  .shelf {
    height: 170px;
  }

  .shelf {
    --shelf-scale: 0.7;
  }

  .spine {
    width: 28px;
  }
}

@media (max-width: 520px) {
  .brand span {
    display: none;
  }

  .stats {
    grid-template-columns: 1fr;
  }

  .stat {
    grid-template-columns: auto 1fr;
    align-items: baseline;
    gap: 0.75rem;
  }

  .book-grid {
    grid-template-columns: 1fr;
  }
}

/* ---------- Reduced motion: switch movement off ---------- */

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    transition-delay: 0s !important;
    scroll-behavior: auto !important;
  }

  .drift-book {
    display: none;
  }
}