/* Paper sheet container */
.sheet {
  width: 100%;
  max-width: 580px;
  height: calc(100vh - 24px);
  height: calc(100dvh - 24px);
  margin: 12px auto;
  background: var(--sheet-bg);
  box-shadow: 
    0 1px 3px rgba(45, 30, 15, 0.06),
    0 10px 25px -5px rgba(45, 30, 15, 0.08),
    0 0 0 1px rgba(70, 50, 30, 0.04);
  position: relative;
  display: flex;
  flex-direction: column;
  border-radius: 4px;
  transition: transform 0.25s ease, opacity 0.25s ease;
  z-index: 1;
  animation: sheetShadowBreath 12s cubic-bezier(0.4, 0, 0.2, 1) infinite;
  overflow: hidden;
}

@media (max-width: 600px) {
  .sheet {
    height: 100dvh;
    margin: 0 auto;
    border-radius: 0;
  }
}

@keyframes sheetShadowBreath {
  0%, 100% {
    box-shadow: 
      0 1px 3px rgba(45, 30, 15, 0.04),
      0 8px 18px -5px rgba(45, 30, 15, 0.05),
      0 0 0 1px rgba(70, 50, 30, 0.035);
  }
  42%, 52% {
    box-shadow: 
      0 4px 14px rgba(45, 30, 15, 0.08),
      0 22px 45px -5px rgba(45, 30, 15, 0.13),
      0 0 0 1px rgba(70, 50, 30, 0.05);
  }
}

@keyframes sheetMobileBreath {
  0%, 100% {
    background-color: var(--sheet-bg);
  }
  42%, 52% {
    background-color: #FFFDF7;
  }
}

@media (prefers-reduced-motion: reduce) {
  .ambient-breathing-aura::before,
  .ambient-breathing-aura::after,
  .aura-orb,
  body,
  .sheet {
    animation: none !important;
  }
}

/* Left notebook margin line */
.sheet::before {
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  left: 56px;
  width: 1.5px;
  background-color: var(--margin-line);
  pointer-events: none;
  z-index: 2;
}

/* Header */
header {
  padding: 34px 24px 22px 72px;
  border-bottom: 1px solid var(--paper-border);
  position: relative;
}

/* Header Separation Strip (Notebook Binding Rule) */
.header-sep-strip {
  height: 10px;
  background: var(--slot-bg);
  border-bottom: 1px solid var(--paper-line);
  position: relative;
  flex-shrink: 0;
}

.header-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 4px;
}

.header-install-btn {
  display: none;
  align-items: center;
  gap: 5px;
  background: rgba(85, 60, 35, 0.05);
  border: 1px solid var(--paper-border);
  border-radius: 14px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 500;
  color: var(--ink-secondary);
  font-family: inherit;
  cursor: pointer;
  -webkit-user-select: none;
  user-select: none;
  -webkit-touch-callout: none;
  transition: background-color 0.15s, color 0.15s, transform 0.1s;
}
.header-install-btn:hover {
  background: rgba(85, 60, 35, 0.1);
  color: var(--ink-primary);
}
.header-install-btn:active {
  transform: scale(0.96);
}
.header-install-btn svg {
  opacity: 0.75;
}

h1 {
  font-family: var(--heading-font);
  font-size: 32px;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--ink-primary);
}

.zen-tagline {
  font-size: 12px;
  color: var(--ink-secondary);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  font-weight: 500;
}
.view-mode-indicator {
  font-size: 12.5px;
  color: var(--ink-secondary);
  font-style: italic;
  font-weight: 500;
}

.header-datetime {
  font-size: 13.5px;
  color: var(--ink-secondary);
  letter-spacing: 0.01em;
  margin-top: 3px;
  -webkit-user-select: none;
  user-select: none;
  -webkit-touch-callout: none;
  font-weight: 500;
}

.header-title-wrap {
  display: flex;
  align-items: center;
  gap: 10px;
}

/* Sleep Mode Zen Banner */
.sleep-banner {
  position: absolute;
  bottom: 24px;
  left: 72px;
  right: 92px;
  background: #FAF3E6;
  border: 1px solid var(--paper-border);
  border-radius: 8px;
  padding: 12px 14px;
  box-shadow: 0 2px 8px rgba(45, 30, 15, 0.05);
  z-index: 10;
  display: flex;
  flex-direction: column;
  gap: 4px;
  pointer-events: auto;
  transition: opacity 0.3s ease, transform 0.3s ease;
}

.sleep-banner-close {
  position: absolute;
  top: 8px;
  right: 10px;
  background: transparent;
  border: none;
  font-size: 13px;
  line-height: 1;
  color: var(--ink-secondary);
  cursor: pointer;
  opacity: 0.55;
  padding: 3px 6px;
  border-radius: 4px;
  transition: opacity 0.15s ease, background-color 0.15s ease;
}
.sleep-banner-close:hover {
  opacity: 0.95;
  background: rgba(70, 50, 30, 0.08);
}

.sleep-banner-title {
  font-size: 11.5px;
  font-weight: 600;
  color: #73532C;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  display: flex;
  align-items: center;
  gap: 6px;
  padding-right: 20px;
}

.sleep-banner-body {
  font-size: 12.5px;
  line-height: 1.45;
  color: var(--ink-secondary);
  font-family: var(--body-font);
  font-style: italic;
}