/* tip: ux26-open-pages held-book-s10-ux26-20261028 — dual pages: cover palette shell + left title + right summary; keep ux25 frame/plate */

/* ux14: kill :hover / expand lift while extracting — freeze resting rect */
.cover.is-extracting,
.cover.is-extracting:hover,
.spine.is-extracting,
.spine.is-extracting:hover,
.spine.is-extracting.is-expanded {
  transform: none !important;
  box-shadow: none !important;
  transition: none !important;
}

@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@400;500&family=Noto+Serif+SC:wght@500;600&display=swap');

:root {
  --wall: #faf9f5;
  --ink: #1b1a18;
  --muted: #6e6b64;
  --faint: #a09b91;
  --rail-top: #e8e2d4;
  --rail-bot: #cfc7b6;
  --rail-shadow: rgba(60, 50, 30, 0.08);
  --line: #e6e3dc;
  --col: 740px;
  --hover-ring: rgba(27, 26, 24, 0.18);
  --hover-lift: 0 10px 22px rgba(40, 30, 20, 0.14);
  --pad: 24px;

  --t-expand: 250ms;
  --t-collapse: 230ms;
  --t-pull: 500ms;
  --t-flip: 1000ms;
  --t-settle: 580ms;
  --t-putback: 500ms;
  --t-land: 480ms;
  --t-veil: 580ms;
  --ease-motion: cubic-bezier(0.32, 0.72, 0, 1);
  --ease-out: var(--ease-motion);
  --ease-in: var(--ease-motion);
  --ease-inout: var(--ease-motion);
  --ease-pull: var(--ease-motion);
}

* { box-sizing: border-box; }
html, body { margin: 0; overflow-x: hidden; overflow-x: clip; }
body {
  background: var(--wall);
  color: var(--ink);
  font-family: "Noto Sans SC", "PingFang SC", sans-serif;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
}

#app { position: relative; min-height: 100vh; overflow-x: hidden; max-width: 100%; }
.shelf-view { overflow-x: hidden; max-width: 100%; }

.page {
  width: min(100%, var(--col));
  max-width: 100%;
  margin: 0 auto;
  padding: 40px var(--pad) 56px;
  overflow-x: hidden;
}

.brand {
  font-size: 13px;
  color: var(--muted);
  letter-spacing: 0.06em;
  margin-bottom: 24px;
}
h1 {
  margin: 0 0 10px;
  font-family: "Noto Serif SC", "Songti SC", serif;
  font-size: clamp(28px, 5vw, 36px);
  font-weight: 600;
}
.lede {
  margin: 0 0 20px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--muted);
}

.qa-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin-bottom: 36px;
  padding: 10px 12px;
  background: rgba(255,255,255,0.45);
  border: 1px solid var(--line);
  border-radius: 6px;
}
.qa-label {
  font-size: 11px;
  color: var(--faint);
  letter-spacing: 0.08em;
  margin-right: 4px;
}
.qa-btn {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink);
  font-size: 12px;
  padding: 5px 10px;
  border-radius: 4px;
  cursor: pointer;
  font-family: inherit;
}
.qa-btn.is-active {
  background: var(--ink);
  color: var(--wall);
  border-color: var(--ink);
}
.qa-hint {
  font-size: 11px;
  color: var(--muted);
  margin-left: auto;
}

.bay { margin-bottom: 36px; min-width: 0; max-width: 100%; }
.row-label {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 12px;
}
.row-label .name {
  font-size: 12px;
  color: var(--muted);
  letter-spacing: 0.12em;
}
.row-label .hint {
  font-size: 11px;
  color: var(--faint);
  letter-spacing: 0.04em;
}

.ledge {
  position: relative;
  padding-bottom: 10px;
  width: 100%;
  max-width: 100%;
  min-width: 0;
  overflow: hidden; /* books scroll inside .covers; rail stays bay-wide */
}
.rail {
  height: 7px;
  width: 100%;
  background: linear-gradient(180deg, var(--rail-top) 0%, var(--rail-bot) 100%);
  border-radius: 1px;
  box-shadow: 0 6px 14px var(--rail-shadow);
}

.covers {
  display: flex;
  align-items: flex-end;
  gap: 14px;
  min-height: 210px;
  padding-bottom: 2px;
  flex-wrap: nowrap;
  /* ux17: density gate must prevent overflow; never scroll-clip half covers */
  overflow-x: visible;
}

/* ux22: mobile — each .covers row is a shelf rail; page X stays put */
@media (hover: none), (max-width: 640px) {
  .covers {
    flex-wrap: nowrap;
    gap: 10px;
    width: 100%;
    max-width: 100%;
    min-width: 0;
    overflow-x: auto;
    overflow-y: hidden;
    -webkit-overflow-scrolling: touch;
    overscroll-behavior-x: contain;
    scrollbar-width: none;
    touch-action: pan-x pan-y;
  }
  .covers::-webkit-scrollbar { display: none; }
  .cover {
    width: 102px;
    flex-shrink: 0;
  }
}

.cover {
  width: 118px;
  height: 178px; /* fallback; JS sets natural aspect height */
  border: none;
  padding: 0;
  display: block;
  cursor: pointer;
  border-radius: 2px 3px 0 0;
  background-color: transparent; /* ux24: no preset plate behind art */
  background-size: contain; /* ux17: ban crop */
  background-position: center top;
  background-repeat: no-repeat;
  box-shadow:
    inset -2px 0 0 rgba(0,0,0,0.12),
    inset 1px 0 0 rgba(255,255,255,0.08),
    0 6px 14px rgba(40, 30, 20, 0.08);
  transform: translateY(0) scale(1);
  transition: transform 0.18s ease, box-shadow 0.18s ease, opacity 0.2s ease;
  position: relative;
  overflow: hidden;
  flex-shrink: 0;
}
.cover:focus-visible {
  transform: translateY(-10px) scale(1.04);
  box-shadow:
    0 0 0 2px rgba(255,255,255,0.85),
    0 0 0 3px var(--hover-ring),
    var(--hover-lift);
  z-index: 2;
  outline: none;
}
@media (hover: hover) and (pointer: fine) {
  .cover:hover {
    transform: translateY(-10px) scale(1.04);
    box-shadow:
      0 0 0 2px rgba(255,255,255,0.85),
      0 0 0 3px var(--hover-ring),
      var(--hover-lift);
    z-index: 2;
  }
}
.cover.is-placeholder {
  /* ux13+ux24: invisible seat — no gray/wood/bk plate while flyer is out */
  opacity: 0 !important;
  visibility: hidden !important;
  background-color: transparent !important;
  background-image: none !important;
  filter: none;
  pointer-events: none;
  box-shadow: none;
  transform: none !important;
}
.cover.is-placeholder > .cover-art {
  visibility: hidden !important;
  opacity: 0 !important;
}
/* ux24: resting covers must show art, never solid bk-* shell */
.cover[class*="img-"] {
  background-color: transparent !important;
}
.cover > .cover-art {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  /* ux25: seat = nat aspect (JS) — contain fills exactly; no letterbox plate */
  object-fit: contain;
  object-position: center top;
  display: block;
  pointer-events: none;
  border-radius: inherit;
  z-index: 0;
}

.spines {
  display: flex;
  align-items: flex-end;
  gap: 4px;
  min-height: 188px;
  flex-wrap: nowrap;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior-x: contain;
  scrollbar-width: none;
}
.spines::-webkit-scrollbar { display: none; }

.spine {
  height: 150px;
  width: 28px;
  border: none;
  padding: 10px 0;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: "Noto Serif SC", serif;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: #F7F3EA;
  cursor: pointer;
  border-radius: 1px 2px 0 0;
  box-shadow:
    inset -1px 0 0 rgba(255,255,255,0.12),
    inset 1px 0 0 rgba(0,0,0,0.18);
  display: flex;
  align-items: center;
  justify-content: center;
  transform: translateY(0) scale(1);
  transition:
    transform 0.16s ease,
    box-shadow 0.16s ease,
    filter 0.16s ease,
    width var(--t-expand) var(--ease-out),
    height var(--t-expand) var(--ease-out),
    margin var(--t-expand) var(--ease-out),
    opacity 0.2s ease,
    background-size var(--t-expand) var(--ease-out);
  flex-shrink: 0;
  position: relative;
  overflow: hidden;
  background-size: contain;
  background-position: center top;
  background-repeat: no-repeat;
}
.spine.thin { width: 18px; font-size: 10px; height: 122px; color: #2A261E; }
.spine.light-text { color: #F7F3EA; }
.spine.dark-text { color: #1b1a18; }
.spine span { pointer-events: none; transition: opacity 120ms ease; }
.spine:focus-visible {
  transform: translateY(-8px) scale(1.06);
  box-shadow:
    0 0 0 2px rgba(255,255,255,0.9),
    0 0 0 3px var(--hover-ring),
    0 8px 16px rgba(40, 30, 20, 0.16);
  filter: brightness(1.08);
  z-index: 2;
  outline: none;
}
@media (hover: hover) and (pointer: fine) {
  .spine:hover {
    transform: translateY(-8px) scale(1.06);
    box-shadow:
      0 0 0 2px rgba(255,255,255,0.9),
      0 0 0 3px var(--hover-ring),
      0 8px 16px rgba(40, 30, 20, 0.16);
    filter: brightness(1.08);
    z-index: 2;
  }
}
.spine.is-placeholder {
  /* ux13: invisible seat — ban gray ghost plate */
  opacity: 0;
  filter: none;
  pointer-events: none;
  box-shadow: none;
  transform: none !important;
}
.spine.is-placeholder span { opacity: 0; }
.cover.is-placeholder.is-landing,
.spine.is-placeholder.is-landing {
  opacity: 0;
  transition: opacity 220ms var(--ease-motion);
}

/* Mode C: temporary expand on spine wall */
/* resting spines: solid hue only; cover image only when expanded */
.spine[class*="img-"] {
  background-image: none !important;
}
.spine.is-expanded[class*="img-"] {
  background-image: unset;
}
.spine.is-expanded.img-clean-code { background-image: url("covers/clean-code.jpg") !important; }
.spine.is-expanded.img-refactoring { background-image: url("covers/refactoring.jpg") !important; }
.spine.is-expanded.img-design-patterns { background-image: url("covers/design-patterns.jpg") !important; }
.spine.is-expanded.img-pragmatic-programmer { background-image: url("covers/pragmatic-programmer.jpg") !important; }
.spine.is-expanded.img-continuous-delivery { background-image: url("covers/continuous-delivery.jpg") !important; }
.spine.is-expanded.img-phoenix-project { background-image: url("covers/phoenix-project.jpg") !important; }
.spine.is-expanded.img-mythical-man-month { background-image: url("covers/mythical-man-month.jpg") !important; }
.spine.is-expanded.img-tdd { background-image: url("covers/tdd.jpg") !important; }
.spine.is-expanded.img-lean-startup { background-image: url("covers/lean-startup.jpg") !important; }
.spine.is-expanded.img-release-it { background-image: url("covers/release-it.jpg") !important; }
.spine.is-expanded.img-sre { background-image: url("covers/sre.jpg") !important; }
.spine.is-expanded.img-team-topologies { background-image: url("covers/team-topologies.jpg") !important; }
.spine.is-expanded.img-accelerate { background-image: url("covers/accelerate.jpg") !important; }
.spine.is-expanded.img-ddd { background-image: url("covers/ddd.jpg") !important; }
.spine.is-expanded.img-microservices { background-image: url("covers/microservices.jpg") !important; }
.spine.is-expanded.img-eaa { background-image: url("covers/eaa.jpg") !important; }
.spine.is-expanded.img-ddia { background-image: url("covers/ddia.jpg") !important; }
.spine.is-expanded.img-fundamentals-sa { background-image: url("covers/fundamentals-sa.jpg") !important; }
.spine.is-expanded.img-implementing-ddd { background-image: url("covers/implementing-ddd.jpg") !important; }
.spine.is-expanded.img-systems-performance { background-image: url("covers/systems-performance.jpg") !important; }
.spine.is-expanded.img-clean-architecture { background-image: url("covers/clean-architecture.jpg") !important; }

.spine.is-expanded {
  width: 100px;
  height: 152px;
  margin: 0 4px 0 2px;
  padding: 0;
  writing-mode: horizontal-tb;
  text-orientation: initial;
  letter-spacing: 0;
  transform: translateY(-10px) scale(1.03);
  box-shadow:
    inset -2px 0 0 rgba(0,0,0,0.14),
    0 0 0 2px rgba(255,255,255,0.9),
    0 0 0 3px var(--hover-ring),
    var(--hover-lift);
  filter: none;
  z-index: 3;
  transition:
    width var(--t-expand) var(--ease-out),
    height var(--t-expand) var(--ease-out),
    margin var(--t-expand) var(--ease-out),
    transform var(--t-expand) var(--ease-out),
    box-shadow var(--t-expand) var(--ease-out);
}
.spine.is-expanded span { opacity: 0; position: absolute; }
.spine.is-collapsing {
  transition:
    width var(--t-collapse) var(--ease-motion),
    height var(--t-collapse) var(--ease-motion),
    margin var(--t-collapse) var(--ease-motion),
    transform var(--t-collapse) var(--ease-motion),
    box-shadow var(--t-collapse) var(--ease-motion),
    background-size var(--t-collapse) var(--ease-motion);
}
/* C collapse: shrink while still "expanded" class — drop cover image to solid hue immediately, never flash a wide black plate */
.spine.is-expanded.is-collapsing {
  width: 28px;
  height: 150px;
  margin: 0;
  padding: 10px 0;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  letter-spacing: 0.16em;
  transform: translateY(0) scale(1);
  filter: none;
  box-shadow:
    inset -1px 0 0 rgba(255,255,255,0.12),
    inset 1px 0 0 rgba(0,0,0,0.18);
  background-image: none !important;
  background-size: auto;
  z-index: 2;
}
.spine.is-expanded.is-collapsing.s-tall { width: 30px; height: 168px; }
.spine.is-expanded.is-collapsing.s-mid { width: 28px; height: 152px; }
.spine.is-expanded.is-collapsing.s-short { width: 24px; height: 136px; }
.spine.is-expanded.is-collapsing.thin { width: 18px; height: 122px; }
.spine.is-expanded.is-collapsing span {
  opacity: 1;
  position: static;
}

.s-tall { height: 168px; width: 30px; }
.s-mid { height: 152px; width: 28px; }
.s-short { height: 136px; width: 24px; }
.spine.is-expanded.s-tall,
.spine.is-expanded.s-mid,
.spine.is-expanded.s-short {
  width: 100px;
  height: 152px;
}

/* book colors */
.bk-clean-code { background-color: #0d1b2a; }
.bk-refactoring { background-color: #7a0d1b; }
.bk-design-patterns { background-color: #0d1b1b; }
.bk-continuous-delivery { background-color: #be2828; }
.bk-phoenix-project { background-color: #3a7ab8; }
.bk-mythical-man-month { background-color: #1b3688; }
.bk-pragmatic-programmer { background-color: #1a1a1a; }
.bk-tdd { background-color: #513688; }
.bk-lean-startup { background-color: #3a3a3a; }
.bk-release-it { background-color: #5a6a88; }
.bk-sre { background-color: #00367a; }
.bk-team-topologies { background-color: #2a6a88; }
.bk-accelerate { background-color: #36445f; }
.bk-ddd { background-color: #1e4a7a; }
.bk-microservices { background-color: #a38851; }
.bk-eaa { background-color: #950d1b; }
.bk-ddia { background-color: #8b3a2f; }
.bk-fundamentals-sa { background-color: #44881b; }
.bk-implementing-ddd { background-color: #b03644; }
.bk-systems-performance { background-color: #00447a; }
.bk-clean-architecture { background-color: #0d1b44; }
.bk-sand { background-color: #c4b7a2; color: #2A261E; }
.bk-cream { background-color: #d2c4ae; color: #2A261E; }

.img-clean-code { background-image: url("covers/clean-code.jpg"); }
.img-refactoring { background-image: url("covers/refactoring.jpg"); }
.img-design-patterns { background-image: url("covers/design-patterns.jpg"); }
.img-pragmatic-programmer { background-image: url("covers/pragmatic-programmer.jpg"); }
.img-continuous-delivery { background-image: url("covers/continuous-delivery.jpg"); }
.img-phoenix-project { background-image: url("covers/phoenix-project.jpg"); }
.img-mythical-man-month { background-image: url("covers/mythical-man-month.jpg"); }
.img-tdd { background-image: url("covers/tdd.jpg"); }
.img-lean-startup { background-image: url("covers/lean-startup.jpg"); }
.img-release-it { background-image: url("covers/release-it.jpg"); }
.img-sre { background-image: url("covers/sre.jpg"); }
.img-team-topologies { background-image: url("covers/team-topologies.jpg"); }
.img-accelerate { background-image: url("covers/accelerate.jpg"); }
.img-ddd { background-image: url("covers/ddd.jpg"); }
.img-microservices { background-image: url("covers/microservices.jpg"); }
.img-eaa { background-image: url("covers/eaa.jpg"); }
.img-ddia { background-image: url("covers/ddia.jpg"); }
.img-fundamentals-sa { background-image: url("covers/fundamentals-sa.jpg"); }
.img-implementing-ddd { background-image: url("covers/implementing-ddd.jpg"); }
.img-systems-performance { background-image: url("covers/systems-performance.jpg"); }
.img-clean-architecture { background-image: url("covers/clean-architecture.jpg"); }

.foot {
  margin-top: 40px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  gap: 16px;
  font-size: 12px;
  color: var(--muted);
  flex-wrap: wrap;
}

/* —— Note view —— */
.note-view {
  position: fixed;
  inset: 0;
  z-index: 60;
  background: #faf9f5; /* solid paper — never translucent wall flash */
  overflow: auto;
  opacity: 0;
  pointer-events: none;
  /* opacity driven by WAAPI / inline — no CSS transition */
  transition: none;
}
.note-view.is-preparing,
.note-view.is-open {
  /* Above stage so note can cover flyer without a kill-flash */
  z-index: 75;
}
.note-view.is-open {
  opacity: 1;
  pointer-events: auto;
}
.note {
  width: min(100%, var(--col));
  margin: 0 auto;
  padding: 32px var(--pad) 80px;
}
.back-btn {
  border: none;
  background: transparent;
  color: var(--muted);
  font-size: 14px;
  cursor: pointer;
  padding: 8px 0;
  margin-bottom: 28px;
  font-family: inherit;
}
.back-btn:hover { color: var(--ink); }
.note-hero {
  display: flex;
  gap: 24px;
  align-items: flex-start;
  margin-bottom: 36px;
}
.note-cover {
  width: 120px;
  height: 180px;
  flex-shrink: 0;
  border-radius: 2px 3px 0 0;
  background-size: cover;
  background-position: center top;
  background-color: #2a2a2a;
  box-shadow: 0 8px 20px rgba(40,30,20,0.12);
}
.note-cat {
  margin: 0 0 8px;
  font-size: 12px;
  color: var(--muted);
  letter-spacing: 0.1em;
}
.note-meta h1 {
  font-size: clamp(24px, 4vw, 32px);
  margin: 0 0 8px;
}
.note-author {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}
.note-body {
  font-size: 16px;
  line-height: 1.85;
  color: var(--ink);
}
.note-body h2 {
  font-family: "Noto Serif SC", serif;
  font-size: 20px;
  margin: 32px 0 12px;
  font-weight: 600;
}
.note-body p { margin: 0 0 1.1em; }
.note-body ul { padding-left: 1.2em; margin: 0 0 1.1em; }
.note-body li { margin-bottom: 0.4em; }
.note-body .placeholder {
  color: var(--muted);
  font-style: italic;
}

/* —— Stage / backdrop / veil / held-book flyer (§10) —— */
.open-backdrop {
  position: fixed;
  inset: 0;
  z-index: 58;
  pointer-events: none;
  background: #faf9f5;
  opacity: 0;
}
.open-backdrop.is-on {
  /* Soft — shelf can still read through slightly; never the only visible layer */
  opacity: 0.55;
}
.open-backdrop.is-solid {
  opacity: 1;
}

.stage {
  position: fixed;
  inset: 0;
  z-index: 70;
  pointer-events: none;
  perspective: 1800px;
  perspective-origin: 50% 45%;
}

.open-veil {
  position: fixed;
  inset: 0;
  z-index: 80;
  pointer-events: none;
  overflow: hidden;
  opacity: 0;
}
.open-veil.is-on {
  opacity: 1;
}
.open-veil-blob {
  position: absolute;
  width: 280vmax;
  height: 280vmax;
  left: var(--vx, 50%);
  top: var(--vy, 45%);
  margin-left: -140vmax;
  margin-top: -140vmax;
  border-radius: 50%;
  background:
    radial-gradient(
      circle at center,
      #fffcf6 0%,
      #faf9f5 42%,
      #faf9f5 100%
    );
  transform: translateZ(0) scale(0);
  transform-origin: center center;
  will-change: transform, opacity;
  opacity: 1;
}

.flyer {
  position: fixed;
  left: 0;
  top: 0;
  width: 680px;
  height: 400px;
  margin: 0;
  transform-origin: top left;
  /* FLAT: scaling a preserve-3d parent causes shimmer/jitter */
  transform-style: flat;
  opacity: 1;
  overflow: visible;
  contain: layout style;
}
.flyer.is-ready {
  will-change: transform, opacity;
}

/* Soft oval foot shadow — no filter:blur (blur+anim = jitter) */
.flyer-shadow {
  position: absolute;
  left: 8%;
  right: 8%;
  bottom: -10%;
  height: 28%;
  border-radius: 50%;
  background: radial-gradient(
    ellipse at center,
    rgba(40, 30, 20, 0.16) 0%,
    rgba(40, 30, 20, 0.07) 42%,
    rgba(40, 30, 20, 0.02) 65%,
    rgba(40, 30, 20, 0) 80%
  );
  opacity: 0.4;
  z-index: 0;
  pointer-events: none;
  transform: translate3d(0, 0, 0) scale(1, 0.45);
  will-change: opacity;
}

.flyer-book {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
  transform-origin: center center;
  /* Static mild tilt — do NOT animate rotateX (competes with flyer scale) */
  transform: rotateX(8deg) translate3d(0, 0, 0);
  z-index: 1;
  backface-visibility: hidden;
}

/* Thin cover board peeking under page block (thickness cue) */
.flyer-board {
  position: absolute;
  inset: -2% -1.2% -3.5% -1.2%;
  border-radius: 3px 4px 2px 2px;
  /* ux26: shell = this book's cover dominant (via --shell); ban site-wide brown */
  background: linear-gradient(
    180deg,
    var(--shell-hi, #6a7a98) 0%,
    var(--shell, #5a6a88) 55%,
    var(--shell-lo, #3a4a68) 100%
  );
  box-shadow: 0 1px 0 rgba(255,255,255,0.06) inset;
  transform: translateZ(-8px);
  z-index: 0;
}

.flyer-leaf {
  position: absolute;
  top: 0;
  width: 50%;
  height: 100%;
  transform-style: preserve-3d;
  z-index: 2;
}
.flyer-leaf-left {
  left: 0;
  transform-origin: right center;
}
.flyer-leaf-right {
  left: 50%;
  transform-origin: left center;
}

.flyer-face {
  position: absolute;
  inset: 0;
  border-radius: 2px 3px 0 0;
  overflow: hidden;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}

/* Cover on BACK of left leaf — camera-facing when leaf folded (180°) */
.flyer-face-cover {
  transform: rotateY(180deg);
  background-color: transparent; /* ux24: no preset wood plate */
  /* No background-image here — .img-* / inline applyCoverImage owns the photo.
     Gradients-only used to override img classes → flat brown/gray close flash. */
  box-shadow:
    inset -2px 0 0 rgba(0,0,0,0.18),
    2px 0 10px rgba(40, 30, 20, 0.14);
}
.flyer-face-cover.is-spine-face {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: "Noto Serif SC", serif;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: #F7F3EA;
  display: flex;
  align-items: center;
  justify-content: center;
  background-image:
    linear-gradient(90deg, rgba(0,0,0,0.18) 0%, transparent 10%),
    linear-gradient(180deg, rgba(255,255,255,0.06), transparent 40%);
}
.flyer-spine-label { pointer-events: none; }

/* ux15 plate kept inert; ux16 uses full-height .flyer-spine-slot instead */
.flyer-spine-land-plate {
  position: absolute;
  inset: 0;
  pointer-events: none;
  border-radius: inherit;
  z-index: 1;
  display: none;
}
.flyer-spine-land-plate:not([class*="bk-"]) {
  background: linear-gradient(180deg, var(--shell-hi, #6a7a98) 0%, var(--shell, #5a6a88) 100%);
}

/* ux16: exact homeRect standing spine — full height, spine width, slides out/in */
.flyer.flyer-spine-slot {
  position: fixed;
  margin: 0;
  padding: 10px 0;
  box-sizing: border-box;
  border-radius: 1px 2px 0 0;
  box-shadow:
    inset -1px 0 0 rgba(255,255,255,0.12),
    inset 1px 0 0 rgba(0,0,0,0.18),
    0 6px 14px rgba(40, 30, 20, 0.18);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  pointer-events: none;
  transform-origin: center center;
  contain: layout style;
  will-change: transform, opacity;
}
.flyer-spine-slot-label {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: "Noto Serif SC", serif;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: #F7F3EA;
  pointer-events: none;
  line-height: 1.2;
  max-height: 100%;
  overflow: hidden;
}
.flyer-spine-slot.bk-sand .flyer-spine-slot-label,
.flyer-spine-slot.bk-cream .flyer-spine-slot-label {
  color: #2A261E;
  font-size: 10px;
}
.flyer-face-cover.is-cover-ready {
  writing-mode: horizontal-tb;
}
.flyer-face-cover.is-cover-ready[class*="img-"] {
  background-size: contain !important;
  background-position: center top !important;
  background-repeat: no-repeat !important;
}
.flyer-face-cover.is-cover-ready .flyer-spine-label {
  display: none;
}
.flyer-cover-img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain; /* ux25: mid page aspect = book nat — contain fills, no plate */
  object-position: center top;
  display: block;
  pointer-events: none;
  border-radius: inherit;
  /* Sit under optional spine label; above empty board fill */
  z-index: 0;
  transform: translateZ(0);
}

/* Cream page with gutter shade + micro-arch (radial) — not flat fill */
.flyer-face-page {
  /* ux26: page wash from cover palette (--page*); text --ink */
  background-color: var(--page, #fffcf6);
  background-image:
    radial-gradient(120% 40% at 50% -5%, rgba(255,255,255,0.45) 0%, transparent 55%),
    linear-gradient(180deg, var(--page-hi, #fffcf6) 0%, var(--page, #f7f4ef) 55%, var(--page-lo, #efe8dc) 100%);
  padding: 16px 14px 16px 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  color: var(--ink, #2a261e);
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--shell, #5a6a88) 14%, transparent);
}
.flyer-leaf-left .flyer-face-page {
  background-image:
    radial-gradient(120% 40% at 50% -5%, rgba(255,255,255,0.4) 0%, transparent 55%),
    linear-gradient(90deg, transparent 55%, color-mix(in srgb, var(--shell, #5a6a88) 10%, transparent) 82%, color-mix(in srgb, var(--shell, #5a6a88) 28%, transparent) 100%),
    linear-gradient(180deg, var(--page-hi, #fffcf6) 0%, var(--page, #f7f4ef) 55%, var(--page-lo, #efe8dc) 100%);
  border-radius: 3px 0 0 2px;
  padding-right: 18px;
  justify-content: center;
}
.flyer-leaf-right .flyer-face-page {
  background-image:
    radial-gradient(120% 40% at 50% -5%, rgba(255,255,255,0.4) 0%, transparent 55%),
    linear-gradient(270deg, transparent 55%, color-mix(in srgb, var(--shell, #5a6a88) 10%, transparent) 82%, color-mix(in srgb, var(--shell, #5a6a88) 28%, transparent) 100%),
    linear-gradient(180deg, var(--page-hi, #fffcf6) 0%, var(--page, #f7f4ef) 55%, var(--page-lo, #efe8dc) 100%);
  border-radius: 0 3px 2px 0;
  padding-left: 18px;
  justify-content: flex-start;
  padding-top: 18px;
}

/* Page-block thickness strips on outer fore-edges */
.flyer-thickness {
  position: absolute;
  top: 1%;
  bottom: 2%;
  width: 7px;
  pointer-events: none;
  z-index: 3;
  /* ux26: fore-edge from cover palette, not generic cream paper */
  background:
    repeating-linear-gradient(
      180deg,
      var(--edge-a, #d8cfc0) 0px,
      var(--edge-b, #c4b7a2) 1px,
      var(--edge-c, #b0a08a) 2px,
      var(--edge-a, #d8cfc0) 3px
    );
  box-shadow: 0 0 0 1px color-mix(in srgb, var(--shell, #5a6a88) 22%, transparent);
  opacity: 0.92;
  transform: translateZ(1px);
}
.flyer-leaf-left .flyer-thickness {
  left: -5px;
  border-radius: 1px 0 0 1px;
}
.flyer-leaf-right .flyer-thickness {
  right: -5px;
  border-radius: 0 1px 1px 0;
}

/* Center gutter accent (binding dip) */
.flyer-gutter {
  position: absolute;
  top: 2%;
  bottom: 3%;
  left: 50%;
  width: 14px;
  margin-left: -7px;
  z-index: 4;
  pointer-events: none;
  background: linear-gradient(
    90deg,
    rgba(40, 30, 18, 0) 0%,
    rgba(40, 30, 18, 0.18) 35%,
    rgba(30, 22, 12, 0.32) 50%,
    rgba(40, 30, 18, 0.18) 65%,
    rgba(40, 30, 18, 0) 100%
  );
  opacity: 0;
  transform: translateZ(2px);
}

.flyer-page-title {
  font-family: "Noto Serif SC", "Songti SC", serif;
  font-size: 13px;
  font-weight: 650;
  color: var(--ink, #2a261e);
  line-height: 1.4;
  margin: 0 0 6px;
  letter-spacing: 0.02em;
  opacity: 1; /* ux26: left page shows book title mid-open */
}
.flyer-page-author {
  font-family: system-ui, sans-serif;
  font-size: 9px;
  font-weight: 500;
  color: var(--ink-muted, #5a5348);
  line-height: 1.3;
  margin: 0;
  opacity: 0.85;
}
.flyer-page-kicker {
  font-family: system-ui, sans-serif;
  font-size: 9px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-muted, #5a5348);
  margin: 0 0 8px;
  opacity: 0.75;
}
.flyer-page-summary {
  font-family: "Noto Serif SC", "Songti SC", serif;
  font-size: 10px;
  font-weight: 400;
  color: var(--ink, #2a261e);
  line-height: 1.55;
  margin: 0;
  opacity: 1; /* ux26: right page shows reading-notes summary */
  display: -webkit-box;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 9;
  overflow: hidden;
}
.flyer-page-line {
  display: none; /* ux26: no fake rule lines */
}

/* Note pre-layout: no scrollbar until open (scrollbar on cream void looked like a flash) */
.note-view.is-preparing {
  display: block !important;
  pointer-events: none;
  transition: none;
  overflow: hidden;
}
.note-view.is-open {
  pointer-events: auto;
  overflow: auto;
}

.shelf-view.is-dim {
  /* Backdrop covers shelf — dim is unused during open; keep inert */
  opacity: 1;
}
.shelf-view.is-frozen {
  pointer-events: none !important;
}
/* Freeze cover/spine interactions — keep resting min-height (do NOT inherit/collapse;
   inherit was collapsing .covers 210→~178 and causing +~30px end-frame shelf jump). */
.shelf-view.is-frozen .cover,
.shelf-view.is-frozen .spine {
  transition: none !important;
  transform: none !important;
  filter: none !important;
}
.shelf-view.is-frozen .cover:hover,
.shelf-view.is-frozen .cover:focus-visible,
.shelf-view.is-frozen .spine:hover,
.shelf-view.is-frozen .spine:focus-visible {
  transform: none !important;
  box-shadow: inherit;
  z-index: auto;
}
.shelf-view.is-frozen .spine.is-expanded,
.shelf-view.is-frozen .spine.is-collapsing {
  /* Lock expanded footprint — no collapse animation mid-close */
  transition: none !important;
}


/* Park shelf without display:none — preserves geometry, kills close-end bounce */
.shelf-view.is-parked {
  visibility: hidden !important;
  pointer-events: none !important;
  /* stay in document flow (no height collapse) */
}
.shelf-view,
.spines,
.covers {
  overflow-anchor: none;
}

/* Close path: flat single cover card — durable <img>, no cream/board mid-flight */
.flyer.flyer-close-cover {
  transform-style: flat;
  overflow: hidden;
  border-radius: 2px 3px 0 0;
  box-shadow:
    0 14px 32px rgba(40, 30, 20, 0.2),
    0 1px 0 rgba(255, 255, 255, 0.06) inset;
  contain: layout style paint;
}
.flyer-close-face {
  position: absolute;
  inset: 0;
  border-radius: inherit;
  overflow: hidden;
  background-color: transparent; /* ux24: no preset wood plate */
  background-size: cover;
  background-position: center top;
  background-repeat: no-repeat;
  transform: translateZ(0);
}
.flyer-close-face .flyer-cover-img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain; /* ux17: ban crop */
  object-position: center top;
  display: block;
  pointer-events: none;
  z-index: 1;
  transform: translateZ(0);
}
.flyer-close-face .flyer-spine-label {
  z-index: 2;
}

/* reduced motion */
@media (prefers-reduced-motion: reduce) {
  :root {
    --t-expand: 1ms;
    --t-collapse: 1ms;
    --t-pull: 1ms;
    --t-flip: 1ms;
    --t-settle: 1ms;
    --t-putback: 1ms;
    --t-land: 1ms;
    --t-veil: 1ms;
  }
  .cover, .spine, .note-view, .shelf-view, .flyer, .open-backdrop,
  .flyer-leaf, .flyer-face, .flyer-face-cover, .flyer-spine-label, .flyer-gutter, .open-veil, .open-veil-blob {
    transition: none !important;
    animation: none !important;
  }
}

/* mobile */
@media (max-width: 640px) {
  .page { padding: 28px 16px 40px; }
  .covers { gap: 10px; min-height: 176px; }
  .cover { width: 102px; height: 154px; /* fallback; JS sets nat height */ }
  .spines { min-height: 160px; gap: 3px; }
  .spine { height: 132px; width: 24px; font-size: 11px; }
  .s-tall { height: 148px; width: 26px; }
  .s-mid { height: 134px; width: 24px; }
  .s-short { height: 120px; width: 20px; }
  /* resting spines: solid hue only; cover image only when expanded */
.spine[class*="img-"] {
  background-image: none !important;
}
.spine.is-expanded[class*="img-"] {
  background-image: unset;
}
.spine.is-expanded.img-clean-code { background-image: url("covers/clean-code.jpg") !important; }
.spine.is-expanded.img-refactoring { background-image: url("covers/refactoring.jpg") !important; }
.spine.is-expanded.img-design-patterns { background-image: url("covers/design-patterns.jpg") !important; }
.spine.is-expanded.img-pragmatic-programmer { background-image: url("covers/pragmatic-programmer.jpg") !important; }
.spine.is-expanded.img-continuous-delivery { background-image: url("covers/continuous-delivery.jpg") !important; }
.spine.is-expanded.img-phoenix-project { background-image: url("covers/phoenix-project.jpg") !important; }
.spine.is-expanded.img-mythical-man-month { background-image: url("covers/mythical-man-month.jpg") !important; }
.spine.is-expanded.img-tdd { background-image: url("covers/tdd.jpg") !important; }
.spine.is-expanded.img-lean-startup { background-image: url("covers/lean-startup.jpg") !important; }
.spine.is-expanded.img-release-it { background-image: url("covers/release-it.jpg") !important; }
.spine.is-expanded.img-sre { background-image: url("covers/sre.jpg") !important; }
.spine.is-expanded.img-team-topologies { background-image: url("covers/team-topologies.jpg") !important; }
.spine.is-expanded.img-accelerate { background-image: url("covers/accelerate.jpg") !important; }
.spine.is-expanded.img-ddd { background-image: url("covers/ddd.jpg") !important; }
.spine.is-expanded.img-microservices { background-image: url("covers/microservices.jpg") !important; }
.spine.is-expanded.img-eaa { background-image: url("covers/eaa.jpg") !important; }
.spine.is-expanded.img-ddia { background-image: url("covers/ddia.jpg") !important; }
.spine.is-expanded.img-fundamentals-sa { background-image: url("covers/fundamentals-sa.jpg") !important; }
.spine.is-expanded.img-implementing-ddd { background-image: url("covers/implementing-ddd.jpg") !important; }
.spine.is-expanded.img-systems-performance { background-image: url("covers/systems-performance.jpg") !important; }
.spine.is-expanded.img-clean-architecture { background-image: url("covers/clean-architecture.jpg") !important; }

.spine.is-expanded {
    width: 90px;
    height: 136px;
  }
  .spine.is-expanded.is-collapsing {
    width: 24px;
    height: 132px;
  }
  .spine.is-expanded.is-collapsing.s-tall { width: 26px; height: 148px; }
  .spine.is-expanded.is-collapsing.s-mid { width: 24px; height: 134px; }
  .spine.is-expanded.is-collapsing.s-short { width: 20px; height: 120px; }
  .note-hero { flex-direction: column; gap: 16px; }
  .note-cover { width: 100px; height: 150px; }
  .qa-hint { width: 100%; margin-left: 0; margin-top: 4px; }
}

/* Reading path: hide demo/QA chrome unless ?debug=1 */
body:not(.debug-on) .is-debug { display: none !important; }