/* ───────── 縦書き羊皮紙リーダー ───────── */

:root {
  --room: #17100b;
  --room-2: #2a1d13;
  --ink: #2b1d12;
  --ink-soft: rgba(43, 29, 18, 0.62);
  --parch: #efe0bd;
  --parch-hi: #f7edd3;
  --parch-lo: #d6bd8a;
  --chrome: rgba(236, 219, 184, 0.72);
  --chrome-dim: rgba(236, 219, 184, 0.42);
  --jp-serif: "Hiragino Mincho ProN", "Hiragino Mincho Pro", "Yu Mincho", "YuMincho", "Noto Serif JP", "Source Han Serif JP", "MS PMincho", serif;

  /* procedural textures (SVG feTurbulence, rasterised once by the browser) */
  --grain: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='240' height='240'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.9' numOctaves='3' stitchTiles='stitch'/%3E%3CfeColorMatrix values='0 0 0 0 .32 0 0 0 0 .22 0 0 0 0 .1 0 0 0 .6 0'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='.42'/%3E%3C/svg%3E");
  --fiber: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='420' height='420'%3E%3Cfilter id='f'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.03 .11' numOctaves='2' seed='7' stitchTiles='stitch'/%3E%3CfeColorMatrix values='0 0 0 0 .45 0 0 0 0 .33 0 0 0 0 .16 0 0 0 1.6 -.72'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23f)' opacity='.22'/%3E%3C/svg%3E");
  --mottle: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='600' height='600'%3E%3Cfilter id='m'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.006' numOctaves='4' seed='3' stitchTiles='stitch'/%3E%3CfeColorMatrix values='0 0 0 0 .5 0 0 0 0 .34 0 0 0 0 .12 0 0 0 1.8 -.8'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23m)' opacity='.3'/%3E%3C/svg%3E");

  --sat: env(safe-area-inset-top, 0px);
  --sab: env(safe-area-inset-bottom, 0px);
  --sal: env(safe-area-inset-left, 0px);
  --sar: env(safe-area-inset-right, 0px);
}

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

html, body {
  margin: 0;
  height: 100%;
  overflow: hidden;
  overscroll-behavior: none;
  background: var(--room);
  color: var(--chrome);
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
}

body {
  position: fixed;
  inset: 0;
  font-family: var(--jp-serif);
  user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
}

.app {
  position: fixed;
  inset: 0;
  height: 100vh;
  height: 100svh;
  height: 100dvh;
  display: grid;
  grid-template-rows: auto 1fr auto;
  padding: var(--sat) var(--sar) var(--sab) var(--sal);
  background:
    radial-gradient(120% 80% at 50% 45%, var(--room-2) 0%, var(--room) 70%, #0d0906 100%);
}
.app::before { /* faint grain in the reading-room so it isn't flat black */
  content: "";
  position: absolute;
  inset: 0;
  background-image: var(--grain);
  opacity: 0.18;
  mix-blend-mode: screen;
  pointer-events: none;
}

/* ───────── chrome ───────── */

.chrome {
  position: relative;
  z-index: 5;
  display: flex;
  align-items: center;
  padding: 0 14px;
  transition: opacity 0.35s ease;
}
.app.chrome-hidden .chrome { opacity: 0; pointer-events: none; }

.chrome-top { height: 44px; justify-content: space-between; }
.work-title { display: flex; align-items: baseline; gap: 0.7em; letter-spacing: 0.12em; }
.wt-main { font-size: 15px; font-weight: 600; color: var(--chrome); }
.wt-author { font-size: 11px; color: var(--chrome-dim); }

.icon-btn {
  appearance: none;
  border: 1px solid rgba(236, 219, 184, 0.18);
  background: rgba(255, 240, 210, 0.04);
  color: var(--chrome);
  width: 34px;
  height: 34px;
  border-radius: 9px;
  display: grid;
  place-items: center;
  cursor: pointer;
}
.icon-btn:focus-visible { outline: 2px solid #c9a86a; outline-offset: 2px; }

.chrome-bottom { height: 46px; justify-content: center; flex-direction: column; gap: 2px; }
.indicator {
  margin: 0;
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--chrome-dim);
  font-variant-numeric: tabular-nums;
}
.hint {
  margin: 0;
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--chrome);
  opacity: 0.9;
  transition: opacity 0.8s ease, transform 0.8s ease;
  animation: hint-breathe 2.6s ease-in-out infinite;
}
.hint.gone { opacity: 0; transform: translateY(4px); animation: none; }
@keyframes hint-breathe { 50% { opacity: 0.45; } }

/* ───────── stage + book ───────── */

.stage {
  position: relative;
  min-height: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 4px 10px;
  touch-action: none;
  overscroll-behavior: contain;
  cursor: grab;
  overflow: hidden;
}
.stage.dragging { cursor: grabbing; }

.book {
  position: relative;
  height: 100%;
  max-width: 100%;
  aspect-ratio: 0.7;
  container-type: size;
  border-radius: 3px 6px 6px 3px;
  /* page-block edges peeking out + cast shadow on the table */
  box-shadow:
    1px 1px 0 #e6d3a8,
    2px 2px 0 #c9b286,
    3px 3px 0 #e2cea2,
    4px 4px 0 #b99f72,
    0 18px 40px -10px rgba(0, 0, 0, 0.75),
    0 4px 14px rgba(0, 0, 0, 0.5);
  will-change: transform;
}

.pages { position: absolute; inset: 0; }

/* ───────── parchment ───────── */

.page {
  position: absolute;
  inset: 0;
  overflow: hidden;
  border-radius: inherit;
  color: var(--ink);
  background-color: var(--parch);
  background-image:
    var(--grain),
    var(--fiber),
    var(--mottle),
    radial-gradient(130% 95% at 55% 45%, transparent 55%, rgba(120, 78, 28, 0.28) 100%),   /* vignette */
    radial-gradient(90% 70% at 50% 42%, var(--parch-hi) 0%, var(--parch) 60%, var(--parch-lo) 115%),
    linear-gradient(90deg, rgba(90, 60, 25, 0.16) 0%, transparent 5%, transparent 96%, rgba(255, 250, 235, 0.35) 100%); /* gutter + fore-edge */
  background-size: 240px 240px, 420px 420px, 600px 600px, 100% 100%, 100% 100%, 100% 100%;
  visibility: hidden;
  contain: layout paint style;
}
.page.is-top { visibility: visible; z-index: 2; }
.page.is-under { visibility: visible; z-index: 1; }

/* back side of the turning leaf: a touch darker, text faintly shows through (裏写り) */
.flap {
  z-index: 4;
  transform-origin: 0 0;
  filter: brightness(0.94) saturate(1.05);
  will-change: transform, clip-path;
}
.flap.on { visibility: visible; }
.show-through { position: absolute; inset: 0; opacity: 0.06; filter: blur(0.4px); }

.flap-shade {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 100%;
  z-index: 5;
  pointer-events: none;
  transform-origin: 0 0;
  visibility: hidden;
  background: linear-gradient(90deg,
    rgba(255, 249, 232, 0.10) 0%,
    rgba(255, 249, 232, 0.38) 30%,
    rgba(120, 82, 36, 0.10) 72%,
    rgba(70, 42, 14, 0.38) 100%);
  box-shadow: -14px 0 26px -8px rgba(30, 16, 4, 0.45);
  will-change: transform;
}
.flap-shade.on { visibility: visible; }

.fold-shadow { /* shadow on the revealed page, just past the fold line */
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 70px;
  z-index: 3;
  pointer-events: none;
  visibility: hidden;
  background: linear-gradient(90deg, rgba(40, 22, 6, 0.42), rgba(40, 22, 6, 0.12) 40%, transparent);
  will-change: transform, opacity;
}
.fold-shadow.on { visibility: visible; }

/* ───────── typography ───────── */

.body {
  position: absolute;
  top: 9.5cqh;
  bottom: 8.5cqh;
  right: 8cqw;
  left: 8cqw;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: var(--jp-serif);
  font-size: clamp(15px, 5cqw, 21px);
  line-height: 1.85;
  letter-spacing: 0.05em;
  text-align: justify;
  line-break: strict;
  word-break: normal;
  hanging-punctuation: allow-end;
  white-space: pre-wrap;
  overflow: hidden;
  font-kerning: normal;
  text-rendering: optimizeLegibility;
  /* ink sits into the paper a little */
  text-shadow: 0 0 0.6px rgba(43, 29, 18, 0.35);
}

.hashira {
  position: absolute;
  top: 3.6cqh;
  left: 8cqw;
  font-size: 10px;
  letter-spacing: 0.3em;
  color: var(--ink-soft);
}
.nombre {
  position: absolute;
  bottom: 3.2cqh;
  left: 8cqw;
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--ink-soft);
  font-variant-numeric: tabular-nums;
}

.measure {
  /* Do NOT use visibility:hidden — iOS returns empty glyph rects and breaks pagination. */
  visibility: visible !important;
  opacity: 0;
  z-index: -1;
  pointer-events: none;
  contain: none;
}

/* title page (扉) */
.tobira .body {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2.2em;
  white-space: normal;
  text-align: start;
}
.tobira .t-title {
  font-size: clamp(34px, 13cqw, 58px);
  font-weight: 600;
  letter-spacing: 0.35em;
  margin: 0;
}
.tobira .t-author { font-size: clamp(15px, 5cqw, 20px); letter-spacing: 0.4em; margin: 0; }
.tobira .t-note { font-size: 11px; letter-spacing: 0.15em; color: var(--ink-soft); margin: 0; }
.tobira .seal {
  width: 2.1em;
  height: 2.1em;
  border: 2px solid #a8321f;
  color: #a8321f;
  display: grid;
  place-items: center;
  font-size: 15px;
  border-radius: 3px;
  opacity: 0.8;
  transform: rotate(4deg);
  text-shadow: none;
  writing-mode: horizontal-tb;
}

/* colophon (奥付) */
.okuzuke .body {
  white-space: normal;
  font-size: clamp(13px, 4cqw, 16px);
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  gap: 1.4em;
}
.okuzuke h2 { font-size: 1.25em; margin: 0; letter-spacing: 0.3em; font-weight: 600; }
.okuzuke p { margin: 0; line-height: 1.9; }
.okuzuke .restart {
  appearance: none;
  font: inherit;
  font-size: 0.95em;
  letter-spacing: 0.3em;
  color: var(--parch-hi);
  background: #5a3a1e;
  border: 0;
  border-radius: 4px;
  padding: 1em 0.55em;
  cursor: pointer;
  text-shadow: none;
  box-shadow: 0 2px 6px rgba(40, 20, 0, 0.35);
}
.okuzuke .restart:focus-visible { outline: 2px solid #a8321f; outline-offset: 3px; }

/* edge bump when there is nothing more to turn */
.book.bump { animation: bump 0.36s cubic-bezier(.3, .7, .4, 1); }
@keyframes bump { 30% { transform: translateX(var(--bump, 0px)); } }

@media (prefers-reduced-motion: reduce) {
  .hint { animation: none; }
  .hint, .chrome { transition-duration: 0.12s; }
  .book.bump { animation-duration: 0.12s; }
}