function vivid-toggle
    if set --query VIVID_THEME
        switch $VIVID_THEME
            case '*-light'
                set -gx VIVID_THEME $(string replace -- "-light" "-dark" $VIVID_THEME)
            case '*-dark'
                set -gx VIVID_THEME $(string replace -- "-dark" "-light" $VIVID_THEME)
            case '*'
                return 1
        end
    end
end