:root {
  color-scheme: light;
  --font-scale: 1;
  --ink: #17263a;
  --muted: #617087;
  --paper: rgba(252, 253, 255, 0.96);
  --page-bg: #e8f1f7;
  --navy: #163a5f;
  --navy-2: #245c83;
  --violet: #7a6ea8;
  --line: rgba(31, 62, 91, 0.14);
  --shadow: 0 24px 70px rgba(20, 49, 78, 0.18);
  --safe-top: env(safe-area-inset-top, 0px);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  min-width: 300px;
  background: var(--page-bg);
  color: var(--ink);
  font-family: ui-serif, Georgia, Cambria, "Times New Roman", serif;
  -webkit-font-smoothing: antialiased;
  overscroll-behavior: none;
}

button, textarea { font: inherit; }

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

button { -webkit-tap-highlight-color: transparent; }

.ambient {
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(circle at 85% 5%, rgba(133, 120, 183, 0.3), transparent 38%),
    radial-gradient(circle at 5% 90%, rgba(55, 132, 174, 0.22), transparent 42%);
}

.cover {
  position: fixed;
  inset: 0;
  z-index: 10;
  display: grid;
  place-items: center;
  min-height: 100dvh;
  padding: calc(28px + var(--safe-top)) 24px calc(28px + var(--safe-bottom));
  overflow: hidden;
  background:
    linear-gradient(145deg, rgba(24, 58, 91, 0.92), rgba(35, 105, 143, 0.84) 48%, rgba(117, 96, 154, 0.9)),
    radial-gradient(circle at 20% 20%, #76b1cc, transparent 48%);
  color: #fff;
  transition: opacity .45s ease, visibility .45s ease;
}

.cover::before,
.cover::after {
  content: "";
  position: absolute;
  width: 75vw;
  height: 75vw;
  border-radius: 50%;
  filter: blur(2px);
  opacity: .2;
}

.cover::before { top: -30vw; right: -26vw; background: #d8c8ff; }
.cover::after { bottom: -38vw; left: -22vw; background: #91d7e6; }

.cover.is-closing { opacity: 0; visibility: hidden; }

.cover__inner {
  position: relative;
  z-index: 1;
  width: min(100%, 520px);
  min-height: min(78dvh, 700px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 52px 28px;
  text-align: center;
  border: 1px solid rgba(255,255,255,.28);
  border-radius: 28px;
  background: linear-gradient(150deg, rgba(255,255,255,.12), rgba(255,255,255,.03));
  box-shadow: inset 0 1px rgba(255,255,255,.22), 0 28px 90px rgba(6,24,44,.25);
  backdrop-filter: blur(12px);
}

.cover__mark { font-size: 2.6rem; color: #eef4ff; margin-bottom: 28px; }
.cover__eyebrow { margin: 0 0 18px; font: 600 .78rem/1.2 ui-sans-serif, system-ui, sans-serif; letter-spacing: .22em; text-transform: uppercase; opacity: .75; }
.cover h1 { margin: 0; max-width: 430px; font-size: clamp(2.25rem, 9vw, 4.5rem); line-height: 1.07; font-weight: 500; letter-spacing: -.035em; text-wrap: balance; }
.cover__rule { width: 64px; height: 1px; margin: 36px 0; background: rgba(255,255,255,.62); }
.cover__offline { margin: 18px 0 0; font: 500 .78rem/1.4 ui-sans-serif, system-ui, sans-serif; opacity: .72; }

.primary-button,
.secondary-button {
  border: 0;
  border-radius: 999px;
  cursor: pointer;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-weight: 700;
}

.primary-button { padding: 15px 28px; background: #fff; color: #173c60; box-shadow: 0 10px 26px rgba(10,31,52,.2); }
.secondary-button { padding: 12px 18px; background: var(--navy); color: #fff; }

.app { min-height: 100dvh; padding-top: calc(70px + var(--safe-top)); padding-bottom: calc(86px + var(--safe-bottom)); }

.topbar {
  position: fixed;
  z-index: 5;
  top: 0;
  left: 0;
  right: 0;
  height: calc(70px + var(--safe-top));
  padding: var(--safe-top) 14px 0;
  display: grid;
  grid-template-columns: 48px 1fr 48px;
  align-items: center;
  background: color-mix(in srgb, var(--paper) 90%, transparent);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(18px);
}

.topbar__title { min-width: 0; text-align: center; font-family: ui-sans-serif, system-ui, sans-serif; }
.topbar__title span { display: block; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-size: .9rem; font-weight: 700; }
.topbar__title small { display: block; margin-top: 2px; color: var(--muted); font-size: .68rem; }

.icon-button,
.nav-button,
.bookmark-button {
  display: grid;
  place-items: center;
  border: 0;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
}

.icon-button { width: 44px; height: 44px; border-radius: 14px; font-family: ui-sans-serif, system-ui, sans-serif; font-size: 1.35rem; }
.icon-button:active { background: var(--line); }
.text-icon { font-size: 1rem; font-weight: 750; }

.progress { position: fixed; z-index: 6; top: calc(69px + var(--safe-top)); left: 0; right: 0; height: 2px; }
.progress span { display: block; width: 0; height: 100%; background: linear-gradient(90deg, var(--navy-2), var(--violet)); transition: width .28s ease; }

.reader { width: 100%; min-height: calc(100dvh - 156px); padding: clamp(16px, 4vw, 36px); outline: none; }

.paper {
  width: min(100%, 780px);
  min-height: calc(100dvh - 190px);
  margin: 0 auto;
  padding: clamp(28px, 7vw, 68px) clamp(22px, 8vw, 78px);
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--paper);
  box-shadow: var(--shadow);
  font-size: calc(1.06rem * var(--font-scale));
  line-height: 1.72;
  transition: opacity .16s ease, transform .16s ease;
}

.paper.is-turning { opacity: .12; transform: translateX(var(--turn-direction, 12px)); }
.paper__number { margin: 0 0 34px; color: var(--muted); font: 650 .72rem/1 ui-sans-serif, system-ui, sans-serif; letter-spacing: .16em; text-transform: uppercase; }
.paper h2 { margin: 1.8em 0 .45em; color: var(--navy); font-size: 1.45em; line-height: 1.23; text-align: center; text-wrap: balance; }
.paper h2:first-of-type { margin-top: 0; }
.paper h3 { margin: 1.25em 0 .38em; color: var(--navy-2); font-size: .95em; line-height: 1.35; text-align: center; }
.paper p { margin: .4em 0; }
.paper .crossref { margin-top: -.15em; color: var(--muted); font-size: .9em; text-align: center; }
.paper .declaration { margin: 1.3em 0; padding: 1.1em 1.15em; border-left: 3px solid var(--violet); background: color-mix(in srgb, var(--violet) 8%, transparent); font-weight: 700; letter-spacing: .015em; }
.paper .intro { font-weight: 650; text-align: center; }
.paper .questions { margin: 1em 0 1.35em; padding-left: 1.45em; }
.paper .questions li { margin: .45em 0; padding-left: .25em; }
.paper .page-end { display: block; margin-top: 36px; color: var(--muted); font: 500 .74rem/1 ui-sans-serif, system-ui, sans-serif; text-align: center; }

.notes-page h2 { margin-bottom: .45em; }
.notes-page__hint { color: var(--muted); font: 500 .88em/1.5 ui-sans-serif, system-ui, sans-serif; text-align: center; }
.notes-area {
  width: 100%;
  min-height: min(52dvh, 520px);
  margin-top: 22px;
  padding: 18px 18px 18px 44px;
  resize: vertical;
  border: 1px solid var(--line);
  border-radius: 16px;
  outline: none;
  background:
    linear-gradient(90deg, transparent 30px, rgba(122,110,168,.22) 30px, rgba(122,110,168,.22) 31px, transparent 31px),
    repeating-linear-gradient(transparent, transparent 31px, rgba(31,62,91,.1) 32px);
  color: var(--ink);
  font-size: 1em;
  line-height: 32px;
}
.notes-area:focus { border-color: color-mix(in srgb, var(--violet) 55%, transparent); box-shadow: 0 0 0 3px color-mix(in srgb, var(--violet) 14%, transparent); }
.save-state { display: block; min-height: 20px; margin-top: 10px; color: var(--muted); font: 600 .76rem/1.4 ui-sans-serif, system-ui, sans-serif; text-align: right; }

.page-nav {
  position: fixed;
  z-index: 5;
  left: 50%;
  bottom: calc(12px + var(--safe-bottom));
  transform: translateX(-50%);
  display: grid;
  grid-template-columns: 50px 42px minmax(66px, auto) 50px;
  align-items: center;
  gap: 3px;
  padding: 7px;
  border: 1px solid var(--line);
  border-radius: 20px;
  background: color-mix(in srgb, var(--paper) 94%, transparent);
  box-shadow: 0 14px 40px rgba(18,48,77,.16);
  backdrop-filter: blur(18px);
}
.nav-button { width: 48px; height: 48px; border-radius: 14px; font-size: 2rem; line-height: 1; }
.nav-button:disabled { opacity: .25; cursor: default; }
.nav-button:not(:disabled):active, .bookmark-button:active { background: var(--line); }
.bookmark-button { width: 40px; height: 44px; border-radius: 12px; font-size: 1.65rem; color: var(--violet); }
.page-counter { min-width: 66px; color: var(--muted); font: 650 .78rem/1 ui-sans-serif, system-ui, sans-serif; text-align: center; }

.sheet {
  width: min(92vw, 520px);
  max-height: min(82dvh, 760px);
  padding: 0;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: var(--paper);
  color: var(--ink);
  box-shadow: 0 30px 100px rgba(11,30,50,.36);
}
.sheet::backdrop { background: rgba(8,22,37,.48); backdrop-filter: blur(5px); }
.sheet__header { position: sticky; top: 0; z-index: 1; display: flex; align-items: center; justify-content: space-between; padding: 18px 18px 14px 22px; border-bottom: 1px solid var(--line); background: var(--paper); }
.sheet__header h2 { margin: 0; font-size: 1.25rem; }
.close-button { font-size: 1.75rem; }

.toc-list { padding: 10px 12px 20px; }
.toc-item { width: 100%; display: grid; grid-template-columns: 34px 1fr auto; gap: 10px; align-items: center; padding: 13px 10px; border: 0; border-radius: 13px; background: transparent; color: var(--ink); text-align: left; cursor: pointer; }
.toc-item:hover, .toc-item[aria-current="page"] { background: var(--line); }
.toc-item__number { color: var(--muted); font: 650 .74rem/1 ui-sans-serif, system-ui, sans-serif; }
.toc-item__title { font: 650 .9rem/1.35 ui-sans-serif, system-ui, sans-serif; }
.toc-item__mark { color: var(--violet); font-size: 1.2rem; }

.settings { overflow-y: auto; }
.setting-group { padding: 20px 22px; border-bottom: 1px solid var(--line); }
.setting-group:last-child { border-bottom: 0; }
.setting-group h3 { margin: 0 0 12px; font: 700 .86rem/1.3 ui-sans-serif, system-ui, sans-serif; }
.font-control, .theme-control { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 8px; }
.font-control button, .theme-control button { min-height: 46px; border: 1px solid var(--line); border-radius: 13px; background: transparent; color: var(--ink); cursor: pointer; }
.font-control output { display: grid; place-items: center; color: var(--muted); font: 650 .85rem/1 ui-sans-serif, system-ui, sans-serif; }
.theme-control { grid-template-columns: 1fr 1fr; }
.theme-control button.is-active { border-color: var(--navy-2); background: var(--navy); color: #fff; }
.install-help p { color: var(--muted); font: 500 .84rem/1.55 ui-sans-serif, system-ui, sans-serif; }

body[data-theme="dark"] {
  color-scheme: dark;
  --ink: #edf4fb;
  --muted: #9fb0c1;
  --paper: rgba(20, 30, 43, .97);
  --page-bg: #0e1824;
  --navy: #9bc8e5;
  --navy-2: #82c8ed;
  --violet: #c0afe8;
  --line: rgba(218, 234, 246, .13);
  --shadow: 0 24px 70px rgba(0,0,0,.3);
}

@media (max-width: 520px) {
  .reader { padding: 0; }
  .paper { min-height: calc(100dvh - 156px); border: 0; border-radius: 0; box-shadow: none; }
  .cover__inner { min-height: 76dvh; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; }
}