gitbook/packages/gitbook/src/components/DocumentView/CodeBlock/CodeBlockRenderer.css

.highlight-line {
    @apply grid [grid-template-columns:subgrid] col-span-2 relative ring-1 ring-transparent hover:ring-tint-hover hover:z-[1] rounded;
    @apply only:hover:ring-transparent;
    @apply [counter-increment:line];

    &.highlighted {
        @apply bg-tint-active;
        @apply first:rounded-t-md *:first:mt-1;
        @apply last:rounded-b-md *:last:mb-1;
        @apply rounded-none;
    }

    &:not(.highlighted) + .highlighted {
        @apply rounded-t-md *:mt-1;
    }

    &.highlighted:has(+ :not(.highlighted)) {
        @apply rounded-b-md *:mb-1;
    }

    &:not(.highlighted) + .highlighted:has(+ :not(.highlighted)) {
        @apply rounded-md;
    }
}

.highlight-line-number {
    @apply text-sm text-right pr-3.5 rounded-l pl-2 sticky left-[-3px] bg-gradient-to-r from-80% from-tint-subtle contrast-more:from-tint-base theme-muted:from-tint-base [html.theme-bold.sidebar-filled_&]:from-tint-base to-transparent;
    @apply before:text-tint before:content-[counter(line)];

    .highlight-line.highlighted > & {
        @apply before:text-tint bg-gradient-to-r from-80% from-tint-active to-transparent;
    }
}

.highlight-line-content {
    @apply ml-3 block text-sm;
}