function fig_flow_overall()
%FIG_FLOW_OVERALL  四层主线：题面抽象（L0）、在线三层（L1）、四问主线（L2）、三条闭环（L3）。
%   仅保留分层框图与层标签，图内不放任何说明性文字。

    S = fig_style();
    D = load_data(S, 'flow_overall');
    H = geom_helpers();
    fig = figure('Color', 'w', 'Visible', 'off');
    ax = axes(fig, 'Position', [0.02 0.06 0.96 0.90], ...
              'XLim', [0 100], 'YLim', [0 100], 'Visible', 'off');
    hold(ax, 'on');

    n = numel(D.tags);
    x_tag = 7;                                   % 层标签中心
    x_lo = 15;  x_hi = 99;                       % 框体水平范围
    box_gap = 2.2;                               % 框间距（放箭头）
    pad = 1.4;                                   % 框内左右留白
    band_h = 14;                                 % 层高
    band_gap = 6.5;
    y_top = 96;

    % 统一字号：逐行按量得的文本宽度试算，保证一排框加间距放得下
    fs = ax.FontSize;
    while fs > 8
        need_max = 0;
        for b = 1:n
            labels = D.labels{b};
            m = numel(labels);
            need = sum(cellfun(@(s) H.text_width(ax, s, fs), labels)) ...
                   + 2 * pad * m + box_gap * (m - 1);
            need_max = max(need_max, need);
        end
        if need_max <= x_hi - x_lo
            break;
        end
        fs = fs - 0.5;
    end

    for b = 1:n
        labels = D.labels{b};
        m = numel(labels);
        tw = cellfun(@(s) H.text_width(ax, s, fs), labels);
        avail = (x_hi - x_lo) - box_gap * (m - 1);
        w = (tw + 2 * pad) * avail / sum(tw + 2 * pad);
        y = y_top - band_h - (b - 1) * (band_h + band_gap);
        color = pick_color(S, D.colors{b});
        text(ax, x_tag, y + band_h / 2, D.tags{b}, 'FontSize', fs + 1, ...
             'HorizontalAlignment', 'center', 'VerticalAlignment', 'middle');
        x = x_lo;
        for i = 1:m
            rectangle(ax, 'Position', [x, y, w(i), band_h], 'FaceColor', 'w', ...
                      'EdgeColor', color, 'LineWidth', 1.1);
            text(ax, x + w(i) / 2, y + band_h / 2, labels{i}, 'FontSize', fs, ...
                 'HorizontalAlignment', 'center', 'VerticalAlignment', 'middle', ...
                 'Interpreter', 'none');
            if i < m
                H.arrow(ax, [x + w(i) + 0.25, y + band_h / 2], ...
                        [x + w(i) + box_gap - 0.25, y + band_h / 2], color);
            end
            x = x + w(i) + box_gap;
        end
    end
    hold(ax, 'off');
    fig_save(fig, S, 'flow-overall-architecture.png');
end