@font-face {
  font-family: "Helvetica Neue Local";
  src: local("Helvetica Neue"), local("Helvetica"), local("Arial");
  font-display: swap;
}

:root {
  --bg: #f5f5f2;
  --fg: #0a0a0a;
  --spine-bg: #f5f5f2;
  --spine-fg: #0a0a0a;
  --gray-dark: #6b6b66;
  --line: #1b1b1b;
}

* {
  box-sizing: border-box;
}

html,
body {
  min-height: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: "Helvetica Neue Local", Helvetica, Arial, sans-serif;
  letter-spacing: -0.025em;
}

a {
  color: inherit;
  text-decoration: none;
}

.page {
  min-height: 100svh;
  padding: 20px 24px 0;
}

.intro {
  margin-top: 20px;
  padding-top: 0;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
  min-height: 16vh;
  display: flex;
  align-items: flex-end;
  gap: 26px;
}

.masthead {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
  font-size: 11px;
  line-height: 1;
  font-weight: 700;
  letter-spacing: 0;
}

.masthead-mark,
.status {
  color: var(--gray-dark);
}

h1 {
  margin: 0;
  font-size: clamp(64px, 8.4vw, 132px);
  line-height: 0.79;
  font-weight: 700;
  letter-spacing: -0.087em;
}

.intro-divider {
  align-self: stretch;
  width: 1px;
  background: var(--line);
  margin-top: -20px;
  margin-bottom: -12px;
}

.intro-links {
  display: flex;
  flex-direction: column;
  align-self: flex-start;
  gap: 10px;
  padding-top: 4px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0;
  color: var(--gray-dark);
}

.intro-links a {
  transition: color 200ms ease;
}

.intro-links a:hover {
  color: var(--fg);
}

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

.shelf-stage {
  margin-top: 0;
  padding-bottom: 40px;
}

.shelf-viewport {
  display: flex;
  justify-content: safe center;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 44px 0 0;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.shelf-viewport::-webkit-scrollbar {
  display: none;
  width: 0;
  height: 0;
}

.shelf-track {
  display: flex;
  align-items: flex-end;
  flex: 0 0 auto;
  gap: 3px;
  width: var(--track-w, max-content);
  transform: translateX(var(--center-shift, 0px));
  transition: transform 520ms cubic-bezier(0.22, 0.8, 0.2, 1);
}

.category-filter {
  display: flex;
  gap: 22px;
  align-items: baseline;
  margin-top: 20px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}

.filter-btn {
  border: none;
  background: none;
  padding: 0;
  margin: 0;
  font-family: inherit;
  font-size: 11px;
  line-height: 1;
  font-weight: 700;
  letter-spacing: 0;
  color: var(--gray-dark);
  cursor: pointer;
  transition: color 200ms ease;
}

.filter-btn:hover,
.filter-btn.is-active {
  color: var(--fg);
}

.book {
  position: relative;
  left: 0;
  flex: 0 0 auto;
  width: var(--w, 58px);
  height: var(--h, 280px);
  display: block;
  /* The visible backgrounds belong to the spine and cover faces. Keeping an
     opaque background here masks the preceding book when it shifts into the
     vacated spine footprint during hover. */
  background: transparent;
  cursor: pointer;
  transition: width 520ms cubic-bezier(0.22, 0.8, 0.2, 1), opacity 300ms ease,
    margin-right 520ms cubic-bezier(0.22, 0.8, 0.2, 1), transform 360ms ease,
    left 520ms cubic-bezier(0.22, 0.8, 0.2, 1);
}

.book:hover {
  left: 3px;
  transform: translateY(-8px);
  margin-right: 238px;
  z-index: 5;
}

/* Earlier books move into the open book's former spine footprint. Keep their
   hit areas above that now-invisible anchor so adjacent hovering still works. */
.book.is-before-active {
  z-index: 6;
}

.book.is-highlighted {
  transform: translateY(-40px);
}

/* Isolated 3D context: .book itself stays a plain 2D box (the JS
   translateX shift for closing the gap only ever touches this element),
   while perspective + preserve-3d live entirely inside this wrapper so
   they can't interact with that shift's own compositing layer. Also,
   preserve-3d is only switched on while actually hovered, so at most
   one book is ever a 3D rendering context at a time instead of all 12
   simultaneously -- fewer concurrent 3D contexts for Chrome's
   compositor to juggle. */
.book-persp {
  position: absolute;
  inset: 0;
  perspective: 700px;
}

.book-3d {
  position: absolute;
  inset: 0;
  transform-style: flat;
}

.spine-label {
  position: absolute;
  inset: 0;
  z-index: 2;
  overflow: hidden;
  pointer-events: none;
  transform-origin: right center;
  transition: transform 520ms cubic-bezier(0.22, 0.8, 0.2, 1),
    opacity 180ms ease 120ms;
}

.book:hover .spine-label {
  transform: scaleX(0.04);
  opacity: 0;
}

.book:hover .book-3d {
  transform-style: preserve-3d;
}

.face-spine,
.face-cover {
  position: absolute;
  top: 0;
  height: 100%;
  backface-visibility: hidden;
  transition: transform 520ms cubic-bezier(0.22, 0.8, 0.2, 1);
}

.face-spine {
  left: 0;
  width: 100%;
  background: var(--spine-bg);
  border: 1px solid var(--line);
  overflow: hidden;
  transform-origin: right center;
  transform: rotateY(0deg);
}

.face-cover {
  left: 100%;
  width: 230px;
  height: 100%;
  background: var(--spine-bg);
  border: 1px solid var(--line);
  transform-origin: left center;
  transform: rotateY(92deg);
  overflow: hidden;
}

.cover-text {
  position: absolute;
  left: 18px;
  right: 18px;
  top: calc(28px + var(--top-offset, 0px));
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.cover-category {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--gray-dark);
}

.cover-title {
  font-size: 15px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.15;
  color: var(--fg);
}

.cover-cta {
  position: absolute;
  left: 18px;
  right: 18px;
  bottom: 18px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 10px;
  line-height: 1;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--gray-dark);
}

.cover-cta span {
  font-size: 15px;
  color: var(--fg);
}

.book:hover .face-spine {
  transform: rotateY(-92deg);
}

.book:hover .face-cover {
  transform: rotateY(0deg);
}

.book-open-content {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: flex-start;
  text-align: left;
  gap: 8px;
  padding: 22px;
  background: var(--spine-bg);
  color: var(--spine-fg);
  border-radius: 0;
  overflow: hidden;
  opacity: 0;
  transition: opacity 260ms ease 140ms;
  pointer-events: none;
}

.open-category {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--gray-dark);
}

.open-title {
  font-size: clamp(18px, 2vw, 24px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.05;
}

.open-meta {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--gray-dark);
}

.open-description {
  margin-top: 8px;
  font-size: 11px;
  font-weight: 400;
  line-height: 1.55;
  letter-spacing: 0;
  color: #4a4a45;
}

/* ---- spine typography ---- */

.spine-label .book-title {
  position: absolute;
  left: 50%;
  bottom: 82px;

  writing-mode: vertical-rl;
  transform: translateX(-50%) rotate(180deg);

  font-size: clamp(12px, 1.1vw, 16px);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1;
  white-space: nowrap;
  color: var(--fg);
  margin: 0;
}

.spine-label .book-sub {
  position: absolute;
  left: 50%;
  bottom: 28px;

  writing-mode: vertical-rl;
  transform: translateX(-50%) rotate(180deg);

  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.01em;
  color: var(--gray-dark);
  white-space: nowrap;
  margin: 0;
}

.shelf-plank {
  height: 1px;
  margin-top: 0;
  background: var(--line);
}

.credit {
  position: fixed;
  right: 12px;
  bottom: 8px;
  z-index: 5;
}

.credit a,
.credit span {
  font-size: 9px;
  font-weight: 400;
  letter-spacing: 0;
  color: var(--gray-dark);
  opacity: 0.6;
  transition: opacity 200ms ease;
}

.credit a:hover {
  opacity: 1;
  text-decoration: underline;
  text-underline-offset: 2px;
}

@media (max-width: 640px) {
  .page {
    padding: 14px 12px 0;
  }

  h1 {
    font-size: clamp(52px, 18vw, 96px);
  }

  .intro {
    flex-direction: column;
    align-items: flex-start;
    gap: 14px;
  }

  .intro-links {
    align-items: flex-start;
    flex-direction: row;
    gap: 18px;
    padding-bottom: 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  .book,
  .face-cover,
  .face-spine {
    transition-duration: 1ms;
  }
}

/* ---- Mobile: Card Grid Layout ---- */
@media (max-width: 768px) {
  .shelf-stage {
    padding-bottom: 20px;
  }

  .shelf-viewport {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
    overflow: visible;
    padding: 24px 0 0;
    max-width: 100%;
  }

  .shelf-track {
    display: contents;
  }

  .book {
    position: relative;
    left: auto;
    width: auto;
    height: auto;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: flex-start;
    padding: 20px;
    background: var(--spine-bg);
    border: 1px solid var(--line);
    gap: 12px;
    margin-right: 0;
    transform: none;
    transition: all 200ms ease;
  }

  .book:hover {
    left: auto;
    transform: translateY(0);
    margin-right: 0;
    background: #efefec;
  }

  .book.is-highlighted {
    transform: none;
  }

  .book-persp,
  .book-3d,
  .spine-label {
    display: none;
  }

  .book-open-content {
    position: static;
    opacity: 1;
    pointer-events: auto;
    background: transparent;
    color: var(--fg);
    padding: 0;
    gap: 4px;
  }

  .open-category {
    font-size: 10px;
  }

  .open-title {
    font-size: 18px;
  }

  .open-meta {
    font-size: 10px;
  }

  .open-description {
    margin-top: 8px;
    font-size: 14px;
    line-height: 1.5;
  }

  .shelf-plank {
    display: none;
  }

  .category-filter {
    display: none;
  }

  .credit {
    position: static;
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px solid var(--line);
  }

  .credit a,
  .credit span {
    font-size: 10px;
  }
}