function selectPhaseDiagramPoints(PhaseDiagramMatrix, NumberOfAtoms, ScatteringLengths, savePath)
% Interactive point selector for phase diagram.
% - Single click to select a point (plotted in red)
% - Double click to remove nearest point
% - Save points to a MAT file using savePath

    xlen = length(NumberOfAtoms);
    ylen = length(ScatteringLengths);

    selectedIndices = [];
    selectedValues = [];
    plottedPoints = [];  % handles of plotted markers

    % Create figure and axes
    fig = figure('Name', 'Interactive Phase Diagram', 'Position', [100, 100, 1600, 900]);
    ax = axes(fig);
    imagesc(ax, PhaseDiagramMatrix);
    set(ax, 'YDir', 'normal');
    colormap(ax, parula);
    colorbar(ax);
    axis(ax, 'equal', 'tight');
    hold(ax, 'on');  % This is crucial!

    % Style
    set(ax, 'FontSize', 16, 'Box', 'On', 'Linewidth', 2);
    xticks(ax, 1:xlen);
    yticks(ax, 1:ylen);
    xticklabels(ax, string(NumberOfAtoms));
    yticklabels(ax, string(ScatteringLengths));
    xlabel(ax, 'Number of Atoms', 'FontSize', 16);
    ylabel(ax, 'Scattering Length (\times a_o)', 'FontSize', 16);
    grid(ax, 'on');

    % Save Button
    uicontrol('Style', 'pushbutton', ...
              'String', 'Save Points', ...
              'FontSize', 12, ...
              'Position', [20 20 120 40], ...
              'Callback', @savePoints);

    % Set callback on axes, not on image
    fig.WindowButtonDownFcn = @handleClick;
    
    selectedIndices = zeros(0, 2);  % ← ensure it's Nx2, not just []
    selectedValues  = zeros(0, 2);
    plottedPoints   = gobjects(0);  % empty graphics array


    function handleClick(~, ~)
        try
            clickType = get(fig, 'SelectionType');
            cp = get(ax, 'CurrentPoint');
            xClick = round(cp(1, 1));
            yClick = round(cp(1, 2));

            if xClick < 1 || xClick > xlen || yClick < 1 || yClick > ylen
                return;
            end

            if strcmp(clickType, 'normal')  % Single click = add point
                alreadySelected = any(ismember(selectedIndices, [xClick, yClick], 'rows'));
                if ~alreadySelected
                    selectedIndices(end+1, :) = [xClick, yClick];
                    selectedValues(end+1, :) = [NumberOfAtoms(xClick), ScatteringLengths(yClick)];
                    h = plot(ax, xClick, yClick, 'r*', 'MarkerSize', 10, 'LineWidth', 1.5);
                    plottedPoints(end+1) = h;
                    fprintf('Selected: N = %.2f, a = %.2f\n', NumberOfAtoms(xClick), ScatteringLengths(yClick));
                end

            elseif strcmp(clickType, 'open')  % Double click = remove point
                if isempty(selectedIndices), return; end
                dists = vecnorm(selectedIndices - [xClick, yClick], 2, 2);
                [minDist, idx] = min(dists);
                if minDist <= 1
                    fprintf('Removed: N = %.2f, a = %.2f\n', selectedValues(idx,1), selectedValues(idx,2));
                    delete(plottedPoints(idx));
                    selectedIndices(idx, :) = [];
                    selectedValues(idx, :) = [];
                    plottedPoints(idx) = [];
                end
            end

        catch ME
            fprintf('Error in handleClick:\n%s\n', getReport(ME, 'extended'));
        end
    end


    function savePoints(~, ~)
        if isempty(selectedValues)
            warndlg('No points selected.', 'Save Warning');
            return;
        end
        SelectedPoints.indices = selectedIndices;
        SelectedPoints.values = selectedValues;
        save(savePath, 'SelectedPoints');
        msgbox(sprintf('Saved %d points to:\n%s', size(selectedValues,1), savePath), 'Saved');
    end
end