:root {
  --canvas: #f2f0e6;
  --ink-primary: #593c31;
  --ink-secondary: rgba(89, 60, 49, 0.7);
  --ink-tertiary: rgba(89, 60, 49, 0.4);
  --accent-red: #962d22;
  --accent-green: #5c7c4c;
  --accent-tan: #b88d5b;
  --accent-blue: #4a6fa5;

  --font-serif: 'Noto Serif SC', Georgia, serif;
  --font-sans: 'Noto Sans SC', 'Inter', -apple-system, sans-serif;

  --safe-top: env(safe-area-inset-top, 0px);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background-color: var(--canvas);
  color: var(--ink-primary);
  font-family: var(--font-sans);
  line-height: 1.7;
  min-height: 100vh;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
}

.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  padding: 1rem 1.25rem calc(1rem + var(--safe-top));
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 100;
}

.brand {
  font-family: var(--font-serif);
  font-size: 1.125rem;
  letter-spacing: 0.02em;
}

.progress {
  font-size: 0.875rem;
  color: var(--ink-secondary);
  font-variant-numeric: tabular-nums;
}

.env-badge {
  position: fixed;
  top: calc(58px + var(--safe-top));
  right: 1.25rem;
  z-index: 100;
  font-size: 10px;
  letter-spacing: 0.08em;
  color: var(--ink-secondary);
  border: 1px solid var(--ink-tertiary);
  background: rgba(255, 255, 255, 0.7);
  padding: 0.2rem 0.45rem;
}

.status {
  position: fixed;
  top: calc(58px + var(--safe-top));
  left: 50%;
  transform: translateX(-50%);
  font-size: 12px;
  color: var(--ink-secondary);
  z-index: 100;
  min-height: 16px;
}

.card-container {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 100%;
  max-width: 640px;
  height: 80vh;
  padding: 0 1rem;
}

.swipe-indicator {
  position: relative;
  z-index: 3;
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.35rem 0.55rem;
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid var(--ink-tertiary);
  opacity: 0;
  transform: scale(0.92);
  transition: opacity 0.12s ease, transform 0.12s ease;
  pointer-events: none;
  white-space: nowrap;
}

.swipe-indicator-left {
  color: var(--accent-green);
  border-color: rgba(92, 124, 76, 0.45);
  justify-self: start;
}

.swipe-indicator-right {
  color: var(--accent-blue);
  border-color: rgba(74, 111, 165, 0.45);
  justify-self: end;
}

.flash-card {
  width: 100%;
  height: 100%;
  background: white;
  border: 1px solid var(--ink-tertiary);
  display: flex;
  flex-direction: column;
  box-shadow: 0 4px 24px rgba(89, 60, 49, 0.08);
  transition: transform 0.22s ease, box-shadow 0.22s ease, border-color 0.22s ease;
  touch-action: pan-y;
}

.flash-card.dragging {
  transition: none;
}

.flash-card[data-action="got-it"] {
  border-color: var(--accent-green);
  box-shadow: 0 14px 36px rgba(92, 124, 76, 0.18);
}

.flash-card[data-action="read-again"] {
  border-color: var(--accent-blue);
  box-shadow: 0 14px 36px rgba(74, 111, 165, 0.18);
}

.card-header {
  padding: 1.25rem 1.5rem 0.75rem;
  border-bottom: 1px solid rgba(89, 60, 49, 0.08);
  flex-shrink: 0;
}

.card-top-rail {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.95rem 1rem 0.7rem;
}

.card-tags {
  min-width: 0;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.45rem;
}

.card-tags-inline {
  margin-bottom: 1rem;
}

.tag {
  min-width: 0;
  padding: 0.3rem 0.5rem;
  border: 1px solid var(--ink-tertiary);
  font-size: 0.75rem;
  color: var(--ink-primary);
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.tag.concept {
  border-color: var(--accent-red);
  color: var(--accent-red);
}

.tag.topic {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.tag.entity {
  border-color: var(--accent-green);
  color: var(--accent-green);
}

.card-body {
  flex: 1;
  padding: 1.25rem 1.5rem;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
  scrollbar-color: rgba(89, 60, 49, 0.2) transparent;
}

.card-body::-webkit-scrollbar { width: 4px; }
.card-body::-webkit-scrollbar-thumb {
  background: rgba(89, 60, 49, 0.2);
  border-radius: 2px;
}

.summary-box {
  background: rgba(92, 124, 76, 0.06);
  border-left: 2px solid var(--accent-green);
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
}

.summary-label {
  font-size: 0.6875rem;
  color: var(--accent-green);
  margin-bottom: 0.375rem;
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.summary-text {
  font-size: 0.9375rem;
  line-height: 1.75;
  color: var(--ink-secondary);
}

.content-text {
  font-size: 1rem;
  line-height: 1.9;
  color: var(--ink-primary);
  font-family: var(--font-serif);
  white-space: pre-wrap;
}

.empty-tip {
  color: var(--ink-secondary);
  font-family: var(--font-sans);
}

.card-footer {
  padding: 1rem 1.5rem;
  border-top: 1px solid rgba(89, 60, 49, 0.08);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-shrink: 0;
}

.author-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--ink-tertiary);
  font-size: 0.8125rem;
  transition: color 0.2s;
}

.author-link:hover {
  color: var(--ink-primary);
  text-decoration: underline;
}

.author-avatar {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: #4a6fa5;
  flex-shrink: 0;
}

.key-hint {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  color: var(--ink-tertiary);
  opacity: 0.4;
  pointer-events: none;
  font-size: 0.75rem;
}

.key-hint.left { left: 2rem; }
.key-hint.right { right: 2rem; }

.key-icon {
  width: 40px;
  height: 40px;
  border: 1px solid var(--ink-tertiary);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.125rem;
  background: rgba(255,255,255,0.5);
}

@media (max-width: 768px) {
  .key-hint { display: none; }
  .card-container { height: 85vh; }
}

@media (max-width: 640px) {
  .card-top-rail {
    gap: 0.45rem;
    padding: 0.9rem 0.8rem 0.65rem;
  }

  .swipe-indicator {
    font-size: 0.68rem;
    padding: 0.3rem 0.42rem;
  }

  .tag {
    font-size: 0.68rem;
    padding: 0.28rem 0.35rem;
  }
}