.kb-viewer-shell {
  --kb-ink: #173042;
  --kb-muted: #526875;
  --kb-panel: #eef4f4;
  --kb-border: rgba(19, 59, 72, 0.18);
  --kb-accent: #b64f34;
  width: min(100%, 1180px);
  margin: 1.5rem auto 0;
  overflow: hidden;
  border: 1px solid var(--kb-border);
  border-radius: 0.8rem;
  background: var(--kb-panel);
  box-shadow: 0 18px 55px rgba(17, 48, 64, 0.12);
}

.kb-viewer-toolbar {
  position: relative;
  z-index: 2;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 3.25rem;
  padding: 0.6rem 0.75rem 0.6rem 1rem;
  border-bottom: 1px solid var(--kb-border);
  background: rgba(255, 255, 255, 0.86);
  color: var(--kb-ink);
  backdrop-filter: blur(12px);
}

.kb-viewer-help {
  margin: 0;
  color: var(--kb-muted);
  font-size: 0.84rem;
  line-height: 1.25;
}

.kb-viewer-help-narrow {
  display: none;
}

.kb-viewer-actions {
  display: flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 0.9rem;
}

.kb-viewer-option {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  margin: 0;
  font-size: 0.84rem;
  white-space: nowrap;
  cursor: pointer;
  user-select: none;
}

.kb-viewer-option input {
  width: 1rem;
  height: 1rem;
  margin: 0;
  accent-color: var(--kb-accent);
}

.kb-viewer-reset {
  min-height: 2rem;
  padding: 0.25rem 0.7rem;
  border: 1px solid rgba(23, 48, 66, 0.32);
  border-radius: 0.35rem;
  background: #fff;
  color: var(--kb-ink);
  font: inherit;
  font-size: 0.82rem;
  cursor: pointer;
}

.kb-viewer-reset:hover {
  border-color: var(--kb-accent);
  color: var(--kb-accent);
}

.kb-viewer-reset:focus-visible,
.kb-viewer-option input:focus-visible {
  outline: 3px solid rgba(0, 140, 186, 0.3);
  outline-offset: 2px;
}

.kb-viewer-stage {
  position: relative;
  height: min(70vh, 720px);
  min-height: 430px;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 42%, rgba(255, 255, 255, 0.95) 0, rgba(231, 241, 242, 0.9) 44%, rgba(203, 219, 221, 0.92) 100%);
  cursor: grab;
  touch-action: none;
}

.kb-viewer-stage.is-dragging {
  cursor: grabbing;
}

.kb-viewer-stage canvas {
  display: block;
  width: 100%;
  height: 100%;
  outline: none;
}

.kb-viewer-status {
  position: absolute;
  inset: 0;
  z-index: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.65rem;
  color: var(--kb-muted);
  font-size: 0.9rem;
  pointer-events: none;
  transition: opacity 180ms ease;
}

.kb-viewer-status.is-hidden {
  opacity: 0;
}

.kb-viewer-status.is-error {
  padding: 1rem;
  color: #7d2f20;
  text-align: center;
  pointer-events: auto;
}

.kb-viewer-spinner {
  width: 1.1rem;
  height: 1.1rem;
  border: 2px solid rgba(82, 104, 117, 0.25);
  border-top-color: var(--kb-accent);
  border-radius: 50%;
  animation: kb-spin 750ms linear infinite;
}

.kb-viewer-caption {
  width: min(100%, 1180px);
  margin: 0.65rem auto 1.75rem;
  color: #667780;
  font-size: 0.82rem;
  text-align: right;
}

.kb-viewer-fallback {
  text-align: center;
}

@keyframes kb-spin {
  to { transform: rotate(360deg); }
}

@media (max-width: 760px) {
  .kb-viewer-toolbar {
    align-items: flex-start;
    flex-direction: column;
    gap: 0.55rem;
    padding: 0.7rem 0.75rem;
  }

  .kb-viewer-help-wide {
    display: none;
  }

  .kb-viewer-help-narrow {
    display: inline;
  }

  .kb-viewer-actions {
    width: 100%;
    justify-content: space-between;
    gap: 0.55rem;
  }

  .kb-viewer-stage {
    height: 62vh;
    min-height: 360px;
  }

  .kb-viewer-caption {
    text-align: left;
  }
}

@media (prefers-reduced-motion: reduce) {
  .kb-viewer-spinner {
    animation-duration: 1.5s;
  }
}