@layer blocks {
  /* The sheet's top and bottom bars: a one-cell row with a quarter cell above
     and below, on glass, so the dot grid runs on behind them. Each bar draws
     its own hairline as a shadow, so it adds no height. */
  .bar {
    padding-block: var(--space-quarter);
    min-block-size: calc(var(--space-cell) + 2 * var(--space-quarter));
    align-content: center;
    background: var(--color-bg-glass);
  }
}