Charts — typed helpers

        }, Constants.BASE_TABLE_OPTS);

        // Chart options
        var barChartOption = new BarChartOpts
        {
            barDir = BarDirection.col, // "col",
            barGrouping = ChartBarGrouping.stacked,
            chartColors = Constants.COLORS_CHART,
            invertedColors = new List<string> { "C0504D" },
            showLegend = true,
            showTitle = true,
            // title options
            //titleRotate = 10,
        };
        barChartOption.x = 0.5;
            barChartOption.y = 0.5;
            barChartOption.w = "90%";
            barChartOption.h = "90%";

        barChartOption.titleProps = new ChartPropsTitle
        {
            title = "Chart Title",
            titleFontFace = "Helvetica Neue Thin",
            titleFontSize = 24,
            titleColor = Constants.COLORS_ACCENT[0],
            titlePos = new PositionXY { x = 1.5, y = 0 },
            //titleRotate = 10,
        };
        barChartOption.axisCat = new ChartPropsAxisCat
        {
            // Category axis options
            showCatAxisTitle = true,
            catAxisLabelColor = Constants.COLORS_ACCENT[1],
            catAxisTitleColor = Constants.COLORS_ACCENT[1],
            catAxisTitle = "Cat Axis Title",
            catAxisTitleFontSize = 14
        };
        barChartOption.axisVal = new ChartPropsAxisVal
        {
            // Value axis options
            showValAxisTitle = true,
            valAxisLabelColor = Constants.COLORS_ACCENT[2],
            valAxisTitleColor = Constants.COLORS_ACCENT[2],
            valAxisTitle = "Val Axis Title",
            valAxisTitleFontSize = 14
        };
        // Add bar chart
        slide.addBarChart(Constants.dataChartBar8Series, barChartOption);
    }

    /// <summary>
    /// 使用 <see cref="BarChartOpts"/> 增加 bar 的图表

        slide.addPieChart(Constants.dataChartPieStat, new PieChartOpts
        {
            // position = new PositionProps(0.5, 0.6, 4.0, 3.2),
            x = 0.5,
            y = 0.6,
            w = 4.0,
            h = 3.2,
            chartArea = new ChartAreaProps { fill = "F1F1F1" },
            chartColors = Constants.COLORS_RYGU,
            dataBorder = new BorderProps("F1F1F1", null, 2),

            legendProps = new ChartPropsLegend
            {
                //
                legendPos = LegendPosition.l,
                legendFontFace = "Courier New",
            },
            showLegend = true,
            //
            showLeaderLines = true,
            showPercent = false,
            showValue = true,
            dataLabel = new ChartPropsDataLabel
            {
                dataLabelColor = "FFFFFF",
                dataLabelFontSize = 14,
                dataLabelPosition = DataLabelPosition.bestFit //  "bestFit", // 'bestFit' | 'outEnd' | 'inEnd' | 'ctr'
            }
        });

        // TOP-LEFT: Horizontal bar chart (typed BarChartOpts)
        var optsChartBar1 = new BarChartOpts
        {
            chartArea = new ChartAreaProps { border = new BorderProps(Constants.COLORS_SPECTRUM[0], null, 1) },
            plotArea = new ChartPropsFillLine { fill = "DAE3F3" },
            chartColors = Constants.COLORS_SPECTRUM,
            objectName = "bar chart (top L)",
            altText = "this is the alt text content",
            barDir = BarDirection.bar,
            x = 0.5, y = 0.6, w = 6, h = 3,
            axisCat = new ChartPropsAxisCat
            {
                catAxisLabelColor = Constants.COLORS_ACCENT[0],
                catAxisLabelFontFace = "Helvetica Neue",
                catAxisMajorTickMark = ChartAxisTickMark.@in,
            },
            axisVal = new ChartPropsAxisVal
            {
                valAxisMajorTickMark = ChartAxisTickMark.cross,
            }
        };
        slide.addBarChart(arrDataSersCats, optsChartBar1);

        // TOP-LEFT: Horizontal bar — axis/grid (typed BarChartOpts)
        var optsChartBar1 = new BarChartOpts
        {
            x = 0.5, y = 0.6, w = 6, h = 3,
            barDir = BarDirection.bar,
            plotArea = new ChartPropsFillLine { fill = "F1F1F1" },
            chartColors = Constants.COLORS_ACCENT,
            axisCat = new ChartPropsAxisCat {
                catAxisLabelColor = "CC0000",
                catAxisLabelFontFace = "Helvetica Neue",
                catAxisLabelFontSize = 14,
                catGridLine = new OptsChartGridLine { style = GridLineStyle.none },
                catAxisHidden = true,
            },
            axisVal = new ChartPropsAxisVal
            {
                valGridLine = new OptsChartGridLine { color = "cc6699", style = GridLineStyle.dash, size = 1 },
                valAxisLineColor = "44AA66",
            },
            showLegend = true,
            showTitle = true,
            titleProps = new ChartPropsTitle { title = "catAxisHidden:true, valGridLine/valAxisLine:dash" }
        };
        slide.addBarChart(arrDataRegions, optsChartBar1);

        // TOP-LEFT: Horizontal stacked bar (typed BarChartOpts)
        var optsChartBar1 = new BarChartOpts
        {
            x = 0.5, y = 0.6, w = 6, h = 3,
            chartArea = new ChartAreaProps { fill = "404040" },
            plotArea = new ChartPropsFillLine { fill = "0d0d0d" },
            barDir = BarDirection.bar,
            barGrouping = ChartBarGrouping.stacked,
            chartColors = new List<string> { "F2AF00", "4472C4" },
            axisCat = new ChartPropsAxisCat
            {
                catAxisOrientation = "maxMin",
                catAxisLabelColor = "4472C4",
                catAxisLabelFontFace = "Helvetica Neue",
                catAxisLabelFontSize = 14,
            },
            dataLabel = new ChartPropsDataLabel { dataLabelColor = "FFFFFF" },
            showValue = true
        };
        slide.addBarChart(arrDataRegions, optsChartBar1);

        // TOP-LEFT: Multi-color bars with date formatting (typed BarChartOpts)
        slide.addBarChart(
            new List<OptsChartData> {
                new OptsChartData{
                    name = "Excel Date Values",
                    labels = new List<List<string>> { new List<string> { "37987", "38018", "38047", "38078", "38108", "38139" } },
                    values = new List<double?> { 20, 30, 10, 25, 15, 5 }
                }
            },
            new BarChartOpts
            {
                x = 0.5, y = 0.6, w = "45%", h = 3,
                chartArea = new ChartAreaProps { fill = "404040" },
                barDir = BarDirection.bar,
                chartColors = new List<string> { "0077BF", "4E9D2D", "ECAA00", "5FC4E3", "DE4216", "154384" },
                axisCat = new ChartPropsAxisCat { catAxisLabelColor = "F1F1F1", catLabelFormatCode = "yyyy-mm" },
                axisVal = new ChartPropsAxisVal { valAxisHidden = true },
                showTitle = true,
                titleProps = new ChartPropsTitle { title = "Categories can be Multi-Color", titleColor = "0088CC", titleFontSize = 14 }
            }
        );

        // TOP-LEFT: Horizontal 3D bar (typed Bar3dChartOpts)
        var optsChartBar1 = new Bar3dChartOpts
        {
            x = 0.5, y = 0.6, w = 6.0, h = 3,
            chartArea = new ChartAreaProps { fill = new ShapeFillProps("F1F1F1", 50) },
            barDir = BarDirection.bar,
            barGapWidthPct = 25,
            chartColors = Constants.COLORS_SPECTRUM,
            chartColorsOpacity = 80,
            v3DRotX = 20, v3DRotY = 10, v3DRAngAx = false,
            axisCat = new ChartPropsAxisCat
            {
                catAxisLabelColor = Constants.COLORS_SPECTRUM[1],
                catAxisLabelFontFace = "Arial",
                catAxisLabelFontSize = 10,
            },
            axisSer = new ChartPropsAxisSer
            {
                serAxisLabelFontFace = "Arial",
                serAxisLabelFontSize = 10,
            }
        };
        slide.addBar3dChart(arrDataRegions, optsChartBar1);

        // Tornado (diverging) bar — typed BarChartOpts
        slide.addBarChart(
             new List<OptsChartData> {
                new OptsChartData{ name = "High", labels = new List<List<string>> { new List<string> { "London", "Munich", "Tokyo" } }, values = new List<double?> { 0.2, 0.32, 0.41 } },
                new OptsChartData{ name = "Low", labels = new List<List<string>> { new List<string> { "London", "Munich", "Tokyo" } }, values = new List<double?> { -0.11, -0.22, -0.29 } }
            },
            new BarChartOpts
            {
                x = 0.5, y = 0.5, w = "90%", h = "90%",
                chartArea = new ChartAreaProps { fill = new ShapeFillProps("F1F1F1", 50) },
                axisVal = new ChartPropsAxisVal { valAxisMaxVal = 1, valAxisLineShow = false, valAxisMajorUnit = 0.2 },
                axisCat = new ChartPropsAxisCat { catAxisLineShow = false, catAxisLabelPos = CatAxisLabelPos.low },
                barDir = BarDirection.bar,
                barGrouping = ChartBarGrouping.stacked,
                shadow = new ShadowProps { type = ShadowType.none },
                chartColors = new List<string> { "0077BF", "4E9D2D", "ECAA00", "5FC4E3", "DE4216", "154384" },
                invertedColors = new List<string> { "0065A2", "428526", "C99100", "51A7C1", "BD3813", "123970" },
                barGapWidthPct = 25,
            }
        );

        // FULL SLIDE: line chart (typed LineChartOpts)
        var OPTS_CHART = new LineChartOpts
        {
            x = 0.5, y = 0.6, w = "95%", h = "85%",
            plotArea = new ChartPropsFillLine { fill = "e3e3e3" },
            showLegend = true,
            legendProps = new ChartPropsLegend { legendPos = LegendPosition.r },
            axisCat = new ChartPropsAxisCat { catAxisLabelRotate = 90 },
            axisVal = new ChartPropsAxisVal { valAxisLabelFormatCode = "#,##0" },
            lineSize = 4,
            lineDataSymbolSize = 10,
            lineDataSymbolLineColor = "4472C4",
            lineDataSymbolLineSize = 3,
            chartColors = [COLOR_GRN],
            showTitle = true,
            titleProps = new ChartPropsTitle { title = CHART_DATA.Fedi_MAU.chartTitle, titleColor = "0088CC", titleFontFace = "Arial", titleFontSize = 18 }
        };
        slide.addLineChart(Constants.CHART_DATA.Fedi_MAU.chartData, OPTS_CHART);

        // Top-left: Smooth line with thick line size (typed LineChartOpts)
        var optsChartLine1 = new LineChartOpts
        {
            x = 0.5, y = 0.6, w = 6, h = 3,
            chartArea = new ChartAreaProps { fill = "F1F1F1" },
            chartColors = Constants.COLORS_RYGU,
            lineSize = 8,
            lineSmooth = true,
            showLegend = true,
            legendProps = new ChartPropsLegend { legendPos = LegendPosition.t },
            axisCat = new ChartPropsAxisCat { catAxisLabelPos = CatAxisLabelPos.high }
        };
        slide.addLineChart(Constants.arrDataLineStat, optsChartLine1);

        // Loop over lineDataSymbol shapes (typed LineChartOpts)
        var opts_lineDataSymbol = new List<string> { "circle", "dash", LineDataSymbolType.diamond.ToString().ToLower(), "dot", "none", LineDataSymbolType.square.ToString().ToLower(), "triangle" };
        for (int idx = 0; idx < opts_lineDataSymbol.Count; idx++)
        {
            var opt = opts_lineDataSymbol[idx];
            slide.addLineChart(Constants.arrDataLineStat, new LineChartOpts
            {
                x = (idx < 3 ? idx * intWgap : idx < 6 ? (idx - 3) * intWgap : (idx - 6) * intWgap) + 0.3,
                y = idx < 3 ? 0.5 : idx < 6 ? 2.85 : 5.1,
                w = 4.25, h = 2.25,
                lineCap = ChartLineCap.round,
                lineDataSymbol = Enum.Parse<LineDataSymbolType>(opt, true),
                lineDataSymbolSize = idx == 5 ? 9 : idx == 6 ? 12 : null,
                chartColors = Constants.COLORS_VIVID,
                titleProps = new ChartPropsTitle { title = opt },
                showTitle = true
            });
        }

        // TOP-LEFT: Basic area chart (typed AreaChartOpts)
        var optsChartLine1 = new AreaChartOpts
        {
            x = 0.5, y = 0.6, w = "45%", h = 3.0,
            chartArea = new ChartAreaProps { fill = "e9e9e9" },
            plotArea = new ChartPropsFillLine { fill = "f2f9fc" },
            dataBorder = new BorderProps("F1F1F1", null, 1),
            showTitle = true,
            titleProps = new ChartPropsTitle { title = Constants.CHART_DATA.CeoPayRatio_Comp.chartTitle, titleFontSize = 11, titleColor = "fc0000" },
            axisVal = new ChartPropsAxisVal { valAxisLabelFormatCode = "#-1", valAxisLabelFontSize = 10, valAxisLabelColor = "494949" },
            axisCat = new ChartPropsAxisCat { catAxisLabelFontSize = 10 }
        };
        slide.addAreaChart(Constants.CHART_DATA.CeoPayRatio_Comp.chartData, optsChartLine1);

        // TOP-LEFT: Doughnut chart (typed DoughnutChartOpts)
        var optsChartPie1 = new DoughnutChartOpts
        {
            x = 0.5, y = 0.6, w = 6, h = 6.4,
            chartArea = new ChartAreaProps { fill = "F1F1F1" },
            holeSize = 70,
            showLabel = false, showValue = false, showPercent = true,
            showLegend = true,
            legendProps = new ChartPropsLegend { legendPos = LegendPosition.b },
            chartColors = Constants.COLORS_RYGU,
            dataBorder = new BorderProps("F1F1F1", null, 2),
            dataLabel = new ChartPropsDataLabel { dataLabelColor = "FFFFFF", dataLabelFontSize = 14 },
            showTitle = false,
            titleProps = new ChartPropsTitle { title = "Project Status", titleColor = "33CF22", titleFontFace = "Helvetica Neue", titleFontSize = 24 }
        };
        slide.addDougnutChart(Constants.dataChartPieStat, optsChartPie1);

        // TOP-LEFT: XY scatter (typed ScatterChartOpts)
        var optsChartScat1 = new ScatterChartOpts
        {
            x = 0.5, y = 0.6, w = "45%", h = 3,
            axisVal = new ChartPropsAxisVal {
                valAxisTitle = "Renters", valAxisTitleColor = "428442", valAxisTitleFontSize = 14, showValAxisTitle = true
            },
            lineSize = 0,
            axisCat = new ChartPropsAxisCat {
                catAxisTitle = "Last 6 Months", catAxisTitleColor = "428442", catAxisTitleFontSize = 14, showCatAxisTitle = true
            },
            showLabel = true,
            dataLabel = new ChartPropsDataLabel { dataLabelPosition = DataLabelPosition.b }
        };
        slide.addScatterChart(arrDataScatter1, optsChartScat1);

        // TOP-LEFT: Bubble chart (typed BubbleChartOpts)
        var optsChartBubble1 = new BubbleChartOpts
        {
            x = 0.5, y = 0.6, w = "45%", h = 3,
            chartArea = new ChartAreaProps { fill = "F1F1F1" },
            chartColors = Constants.COLORS_ACCENT,
            chartColorsOpacity = 40,
            dataBorder = new BorderProps("FFFFFF", null, 1),
            dataLabel = new ChartPropsDataLabel
            {
                dataLabelFontFace = "Arial", dataLabelFontSize = 10, dataLabelColor = "363636", dataLabelPosition = DataLabelPosition.r
            },
            showSerName = true,
            showLeaderLines = true
        };
        slide.addBubbleChart(arrDataBubble1, optsChartBubble1);

        // TOP-L: standard radar (typed RadarChartOpts)
        var optsChartRadar1 = new RadarChartOpts
        {
            x = 0.5, y = 0.6, w = 4.0, h = 3.0,
            chartArea = new ChartAreaProps { fill = "F9F9F9" },
            radarStyle = RadarStyle.standard,
            showTitle = true,
            titleProps = new ChartPropsTitle
            {
                titleColor = "7F7F7F", titleFontFace = "Segoe UI", titleFontSize = 12, title = "radarStyle: 'standard'"
            },
            lineDataSymbol = LineDataSymbolType.none
        };
        slide.addRadarChart(arrDataRegions, optsChartRadar1);

        // Two-level category labels — BarChartOpts.catAxisMultiLevelLabels
        var arrDataLabels = new List<List<string>> {
            new List<string> { "Gear", "Bearing", "Motor", "Switch", "Plug", "Cord", "Fuse", "Bulb", "Pump", "Leak", "Seals" },
            new List<string> { "Mechanical", "", "", "Electrical", "", "", "", "", "Hydraulic", "", "" }
        };
        var opts2 = new BarChartOpts
        {
            x = 6.8, y = 0.6, w = 6.0, h = 3,
            chartArea = new ChartAreaProps { fill = "F1F1F1" },
            axisCat = new ChartPropsAxisCat { catAxisMultiLevelLabels = true, catAxisLabelFontFace = "Helvetica Neue Thin" },
            barDir = BarDirection.col, barGapWidthPct = 0
        };
        slide.addBarChart(arrDataRegions, opts2);

        // Three-level category labels (typed BarChartOpts)
        var arrDataRegions = new List<OptsChartData> {
            new OptsChartData{
                name = "Fruits",
                labels = new List<List<string>> {
                    new List<string> { "Q1", "Q2", "Q3", "Q4", "Q1", "Q2", "Q3", "Q4", "Q1", "Q2", "Q3", "Q4", "Q1", "Q2", "Q3", "Q4" },
                    new List<string> { "Apple", "", "", "", "Banana", "", "", "", "Apple", "", "", "", "Banana", "", "", "" },
                    new List<string> { "2024", "", "", "", "", "", "", "", "2025", "", "", "", "", "", "", "" }
                },
                values = new List<double?> { 734, 465, 656, 176, 434, 165, 613, 359, 279, 660, 307, 270, 539, 142, 554, 405 }
            }
        };
        var opts1 = new BarChartOpts
        {
            x = 0.5, y = 0.6, w = 12.3, h = 6.5,
            chartArea = new ChartAreaProps { fill = "F1F1F1", roundedCorners = false },
            axisCat = new ChartPropsAxisCat { catAxisMultiLevelLabels = true },
            chartColors = new List<string> { "C0504D", "C0504D", "C0504D", "C0504D", "FFC000", "FFC000", "FFC000", "FFC000" }
        };
        slide.addBarChart(arrDataRegions, opts1);

        // Typed combo: bar + line on secondary axes
        var comboProps = new ChartOpts
        {
            x = 0.5, y = 0.6, w = 12.3, h = "85%",
            chartArea = new ChartAreaProps { fill = "F1F1F1" },
            barDir = BarDirection.col, barGrouping = ChartBarGrouping.stacked,
            showLegend = true, legendPos = LegendPosition.b,
            showTitle = true, title = Constants.CHART_DATA.EvSales_Vol.chartTitle,
            valAxes = new List<ChartPropsAxisVal>{
                new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Cars Produced (m)", valAxisMaxVal = 20 },
                new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Global Market Share (%)", valAxisMaxVal = 20, valGridLine = new OptsChartGridLine { style = GridLineStyle.none } }
            },
            catAxes = new List<ChartPropsAxisCat> { new ChartPropsAxisCat { catAxisTitle = "Year" }, new ChartPropsAxisCat { catAxisHidden = true } }
        };
        var comboTypes = new List<ChartMulti> {
            new ChartMulti { type = ChartType.bar, data = Constants.CHART_DATA.EvSales_Vol.chartData, options = new ChartOpts { chartColors = Constants.COLORS_SPECTRUM, barGrouping = ChartBarGrouping.stacked } },
            new ChartMulti { type = ChartType.line, data = Constants.CHART_DATA.EvSales_Pct.chartData, options = new ChartOpts { chartColors = new List<string> { "F38940" }, secondaryValAxis = true, secondaryCatAxis = true } }
        };
        slide.addChart(comboTypes, comboProps);

        void doColumnAreaLine()  // Column/Area/Line combo (typed ChartMulti)
        {
            var opts = new ChartOpts {
                x = 0.6, y = 0.6, w = 6.0, h = 3.0,
                barDir = BarDirection.col,
                showLegend = false, showTitle = false,
                valAxisMaxVal = 100, valAxisMajorUnit = 10,
                valAxes = new List<ChartPropsAxisVal> {
                    new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Primary Value Axis" },
                    new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Secondary Value Axis", valGridLine = new OptsChartGridLine { style = GridLineStyle.none } }
                },
                catAxes = new List<ChartPropsAxisCat> {
                    new ChartPropsAxisCat { catAxisTitle = "Primary Category Axis" },
                    new ChartPropsAxisCat { catAxisHidden = true }
                }
            };
            var columnAreaLineCharts = new List<ChartMulti> {
                new ChartMulti { type = ChartType.area, data = new List<OptsChartData> { new OptsChartData { name = "Current", labels = labels, values = new List<double?> { 1, 4, 7, 2, 3 } } }, options = new ChartOpts { chartColors = new List<string> { "00FFFF" }, barGrouping = ChartBarGrouping.standard, secondaryValAxis = true, secondaryCatAxis = true } },
                new ChartMulti { type = ChartType.bar, data = new List<OptsChartData> { new OptsChartData { name = "Bottom", labels = labels, values = new List<double?> { 17, 26, 53, 10, 4 } } }, options = new ChartOpts { chartColors = new List<string> { "0000FF" }, barGrouping = ChartBarGrouping.stacked } },
                new ChartMulti { type = ChartType.line, data = new List<OptsChartData> { new OptsChartData { name = "Current", labels = labels, values = new List<double?> { 5, 3, 2, 4, 7 } } }, options = new ChartOpts { barGrouping = ChartBarGrouping.standard, secondaryValAxis = true, secondaryCatAxis = true } }
            };
            slide.addChart(columnAreaLineCharts, opts);
        }

        // TOP-LEFT: Horizontal bar with shadow (generic addChart)
        var optsChartBar1 = new ChartOpts
        {
            x = 0.5, y = 0.6, w = 6.0, h = 3.0,
            showTitle = true, title = "Large blue shadow",
            barDir = BarDirection.bar, barGrouping = ChartBarGrouping.standard,
            dataLabelColor = "FFFFFF", showValue = true,
            shadow = new ShadowProps { type = ShadowType.outer, blur = 10, offset = 5, angle = 45, color = "0059B1", opacity = 1 }
        };
        // BOTTOM-LEFT: stacked bar with transparent colors
        var optsChartBar3 = new ChartOpts
        {
            x = 0.5, y = 3.8, w = 6.0, h = 3.5,
            showTitle = true, title = "No shadow, transparent colors",
            barDir = BarDirection.bar, barGrouping = ChartBarGrouping.stacked,
            chartColors = new List<string> { "transparent", "5DA5DA", "transparent", "FAA43A" },
            shadow = new ShadowProps { type = ShadowType.none }
        };
        slide.addChart(ChartType.bar, single, optsChartBar1);

        // DEV: >26 columns with invertedColors (generic addChart)
        var letters = Enumerable.Range(0, 26).Select(i => ((char)('A' + i)).ToString()).ToList();
        letters.AddRange(new[] { "AA", "AB", "AC", "AD" });
        var arrDataHighVals = new List<OptsChartData> {
            new OptsChartData { name = "Alphabet Letter Value", labels = new List<List<string>> { letters }, values = new List<double?> { -5, -3, 0, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 } }
        };
        var optsChart = new ChartOpts {
            x = 0.5, y = 0.5, w = "90%", h = "90%",
            barDir = BarDirection.col, showLegend = true,
            chartColors = new List<string> { "154384" }, invertedColors = new List<string> { "0088CC" },
            title = "Chart With >26 Cols", showTitle = true, titleFontSize = 18,
            showCatAxisTitle = true, catAxisTitle = "Letters", catAxisTitleColor = "4286f4", catAxisTitleFontSize = 14,
            showValAxisTitle = true, valAxisTitle = "Column Index", valAxisTitleColor = "c11c13", valAxisTitleFontSize = 16
        };
        slide.addChart(pptx.charts.BAR, arrDataHighVals, optsChart);

        // DEV: 15 line series with valAxisMaxVal (generic addChart)
        int MAXVAL = 20000;
        var months = Constants.MONS;
        var monthCount = months[0].Count;
        var arrDataTimeline = Enumerable.Range(0, 15).Select(idx => new OptsChartData {
            name = $"Series {idx}", labels = months,
            values = Enumerable.Range(0, monthCount).Select(i => (double?)MAXVAL - 29 * idx - 13 * i).ToList()
        } as OptsChartData).ToList();
        var optsChartLine1 = new ChartOpts {
            x = 0.5, y = 0.6, w = "95%", h = "85%",
            plotArea = new ChartPropsFillLine { fill = "F2F9FC" },
            valAxisMaxVal = MAXVAL, showLegend = true, legendPos = LegendPosition.r
        };
        slide.addChart(ChartType.line, arrDataTimeline, optsChartLine1);

        // DEV: labels contain ', ", &, < and > characters
        slide.addChart(
             ChartType.bar,
             new List<OptsChartData> {
                new OptsChartData{
                    name = "Escaped XML chars",
                    labels = new List<List<string>> { new List<string> { "escaped", "xml", "chars", "'", "\"", "&", "<", ">" } },
                    values = new List<double?> { 1.2, 2.3, 2.15, 6.05, 8.01, 2.02, 9.9, 0.9 }
                }
            },
            new ChartOpts {
                x = 0.5, y = 0.6, w = "90%", h = "90%",
                chartArea = new ChartAreaProps { fill = "404040" },
                catAxisLabelColor = "F1F1F1", valAxisLabelColor = "F1F1F1",
                valGridLine = new OptsChartGridLine { color = "7F7F7F" },
                barDir = BarDirection.bar, showValue = true,
                chartColors = Constants.COLORS_ACCENT.Concat(Constants.COLORS_ACCENT).ToList(),
                barGapWidthPct = 25, catAxisOrientation = "maxMin", valAxisOrientation = "maxMin",
                valAxisMaxVal = 10, valAxisMajorUnit = 1
            }
        );

        // DEV: bar + line combo via ChartMulti (generic addChart)
        var labels = new List<List<string>> { new List<string> { "Q1", "Q2", "Q3", "Q4", "OT" } };
        var chartTypes = new List<ChartMulti> {
            new ChartMulti { type = ChartType.bar, data = new List<OptsChartData> { new OptsChartData { name = "Projected", labels = labels, values = new List<double?> { 17, 26, 53, 10, 4 } } }, options = new ChartOpts { barDir = BarDirection.col, chartColors = Constants.COLORS_VIVID } },
            new ChartMulti { type = ChartType.line, data = new List<OptsChartData> { new OptsChartData { name = "Current", labels = labels, values = new List<double?> { 5, 3, 2, 4, 7 } } }, options = new ChartOpts { secondaryValAxis = true, secondaryCatAxis = true } }
        };
        var multiOpts = new ChartOpts {
            x = 0.5, y = 0.6, w = 12.33, h = 6,
            valAxisMaxVal = 100, valAxisMinVal = 0, valAxisMajorUnit = 20,
            valAxes = new List<ChartPropsAxisVal> {
                new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Primary Value Axis" },
                new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Secondary Value Axis", valAxisMajorUnit = 1, valAxisMaxVal = 10, valAxisMinVal = 1, valGridLine = new OptsChartGridLine { style = GridLineStyle.none } }
            },
            catAxes = new List<ChartPropsAxisCat> { new ChartPropsAxisCat { catAxisTitle = "Primary Category Axis" }, new ChartPropsAxisCat { catAxisHidden = true } }
        };
        slide.addChart(chartTypes, null!, multiOpts);

        // DEV: doughnut + image to verify ref counting (typed DoughnutChartOpts)
        var optsChartPie1 = new DoughnutChartOpts();
        optsChartPie1.x = 0.5; optsChartPie1.y = 0.6; optsChartPie1.w = 6.0; optsChartPie1.h = 6.4;
        optsChartPie1.chartArea = new ChartAreaProps { fill = "F1F1F1" };
        optsChartPie1.holeSize = 70;
        optsChartPie1.showLabel = false; optsChartPie1.showValue = false; optsChartPie1.showPercent = true;
        optsChartPie1.showLegend = true; optsChartPie1.legendProps = LegendPosition.b;
        optsChartPie1.chartColors = Constants.COLORS_SPECTRUM;
        optsChartPie1.dataBorder = new BorderProps("F1F1F1", null, 2);
        optsChartPie1.dataLabel = new(); optsChartPie1.dataLabel.dataLabelColor = "FFFFFF"; optsChartPie1.dataLabel.dataLabelFontSize = 14;
        optsChartPie1.showTitle = false;
        optsChartPie1.titleProps = new(); optsChartPie1.titleProps.title = "Project Status"; optsChartPie1.titleProps.titleColor = "33CF22";
        slide.addDougnutChart(Constants.dataChartPieStat, optsChartPie1);
        var imageProps = new ImageProps();
        imageProps.path = Constants.IMAGE_PATHS.ccCopyRemix.path;
        imageProps.x = 6.83; imageProps.y = 0.6; imageProps.w = 6.0; imageProps.h = 6.0;
        slide.addImage(imageProps);

        // DEV: legacy-style bar via property setters (typed BarChartOpts)
        var optsChartBar1 = new BarChartOpts();
        optsChartBar1.x = 0.5; optsChartBar1.y = 0.6; optsChartBar1.w = 6.0; optsChartBar1.h = 3;
        optsChartBar1.chartArea = new ChartAreaProps { fill = (SCHEME_COLORS.bg2) };
        optsChartBar1.plotArea = new ChartPropsFillLine { fill = (SCHEME_COLORS.bg1), border = new BorderProps(SCHEME_COLORS.bg2, null, 1) };
        optsChartBar1.objectName = "bar chart (top L)";
        optsChartBar1.altText = "this is the alt text content";
        optsChartBar1.barDir = BarDirection.bar;
        optsChartBar1.border = new BorderProps("00CE00", null, 3);
        optsChartBar1.fill = "F1F1F1";
        optsChartBar1.axisCat = new ChartPropsAxisCat();
        optsChartBar1.axisCat.catAxisLabelColor = "CC0000";
        optsChartBar1.axisCat.catAxisLabelFontFace = "Helvetica Neue";
        optsChartBar1.axisCat.catAxisLabelFontSize = 14;
        optsChartBar1.axisCat.catAxisOrientation = "maxMin";
        slide.addBarChart(arrDataHighVals, optsChartBar1);

        // DEV: rotated title + invertedColors (typed BarChartOpts)
        var optsChart = new BarChartOpts
        {
            x = 0.5, y = 0.5, w = "90%", h = "90%",
            barDir = BarDirection.col,
            showTitle = true,
            titleProps = new ChartPropsTitle { title = "Rotated Title", titleFontSize = 20, titleRotate = 10 },
            showLegend = true,
            chartColors = Constants.COLORS_CHART,
            invertedColors = new List<string> { "C0504D" },
            axisCat = new ChartPropsAxisCat { showCatAxisTitle = true, catAxisTitle = "Cat Axis Title", catAxisTitleColor = "4286f4", catAxisTitleFontSize = 14 },
            axisVal = new ChartPropsAxisVal { showValAxisTitle = true, valAxisTitle = "Val Axis Title", valAxisTitleColor = "c11c13", valAxisTitleFontSize = 16 }
        };
        slide.addBarChart(arrDataHighVals, optsChart);