chart

Chart — Data Visualization

Activate When

• User invokes /godmode:chart
• User says "create a chart", "visualize this data", "make a graph"
• User says "build a dashboard", "display metrics", "plot this"
• When building reporting pages or analytics dashboards
• When /godmode:plan identifies data visualization tasks
• When /godmode:review flags visualization accessibility or usability issues

Workflow

Step 1: Data & Intent Discovery

Understand the data and what the visualization needs to communicate:

VISUALIZATION DISCOVERY:
Project: <name and purpose>
Data source: <API endpoint | database query | static JSON | CSV | real-time stream>
Data shape: <rows x columns, field names, types>
Audience: <executives | engineers | end-users | public>
Goal: <compare | trend | distribute | correlate | compose | flow | geospatial>
Interactivity: <static | hover tooltips | click-to-filter | drill-down | real-time>
Environment: <React | Vue | Angular | vanilla JS | server-side PDF | Jupyter>
Existing library: <D3.js | Chart.js | Recharts | Plotly | Nivo | Victory | none>
Constraints: <bundle size limit | IE support | print-friendly | offline | color-blind safe>

If the user hasn't specified, ask: "What story should this visualization tell? Who is the audience?"

Step 2: Chart Type Selection

Select the optimal chart type based on the data and communication goal:

CHART TYPE SELECTION:
| Goal | Recommended Chart Types |
|--|--|
| Compare values | Bar (vertical/horizontal), Grouped bar, Lollipop |
| Show trends | Line, Area, Sparkline, Step |
| Show distribution | Histogram, Box plot, Violin, Density |
| Show correlation | Scatter, Bubble, Heatmap (correlation matrix) |
| Show composition | Stacked bar, Treemap, Sunburst, Waffle |
| Show flow/process | Sankey, Alluvial, Chord diagram |
| Show hierarchy | Treemap, Sunburst, Dendrogram, Circle packing |
| Show geographic | Choropleth, Bubble map, Hex bin map |
| Show part-to-whole | Donut, Stacked area, Marimekko |
  ...

Rules:

• Never use pie charts for more than 5 categories — use bar charts instead
• Never use 3D charts — they distort perception and reduce accuracy
• Use line charts only for continuous data (time series) — not categorical
• Prefer horizontal bar charts when labels are long
• Use small multiples over complex multi-series charts when series exceed 5

Step 3: Library Selection & Setup

Choose the right visualization library for the project:

LIBRARY SELECTION:
| Library | Best For | Bundle Size | Learning Curve |
|--|--|--|--|
| D3.js | Custom, complex, | ~90KB | Steep — full control |
|  | unique visualizations |  | over every pixel |
| Chart.js | Standard charts, | ~60KB | Low — declarative |
|  | quick setup, canvas |  | config-based API |
| Recharts | React dashboards, | ~120KB | Low — React-native |
|  | composable charts |  | component API |
| Plotly | Scientific/data | ~1MB | Medium — rich |
|  | analysis, 3D plots |  | interactive charts |

Step 4: Data Transformation

Prepare data for the selected chart type:

DATA TRANSFORMATION:
Source format: <raw data shape — e.g., array of objects, CSV rows, nested JSON>
Target format: <what the chart library expects>

Transformations needed:
  1. <transformation — e.g., group by category, aggregate sum>
  2. <transformation — e.g., pivot rows to columns>
  3. <transformation — e.g., normalize to percentages>
  4. <transformation — e.g., sort descending by value>
  5. <transformation — e.g., compute rolling average>

Missing data strategy: <omit | zero-fill | interpolate | show gap>
  ...

Generate the transformation code:

// Data transformation pipeline
function transformData(raw: RawData[]): ChartData {
  return raw
    .filter(/* remove invalid entries */)
    .map(/* reshape to chart format */)
    .sort(/* order for readability */)

Step 5: Chart Implementation

Build the chart with full configuration:

CHART CONFIGURATION:
| Property | Value |
|--|--|
| Type | <bar | line | scatter | heatmap | ...> |
| Width | <responsive | fixed px> |
| Height | <responsive | fixed px> |
| Aspect ratio | <16:9 | 4:3 | 1:1 | custom> |
| Margins | top=<N> right=<N> bottom=<N> left=<N> |
| Colors | <palette name or hex values> |
| Font family | <system | project font> |
| Animation | <none | enter | update | transition> |
| Legend | <position: top | right | bottom | none> |
  ...

Use the selected library's standard patterns:

• D3.js: SVG with margin convention, scales, axes, data joins
• Recharts: ResponsiveContainer wrapper, declarative component composition
• Chart.js: Canvas-based config object with datasets array
• Plotly: Trace objects with layout configuration

Step 6: Responsive Design

Mobile (<480px): stack legend below, reduce ticks, enlarge touch targets. Tablet (480-1024px): side legend, full interactivity. Desktop (>1024px): full layout, annotations, brush/zoom.

Step 7: Color & Accessibility

Design accessible visualizations that work for everyone:

ACCESSIBILITY CHECKLIST:
| Check | Status |
|--|--|
| Color contrast ratio >= 3:1 against background | PASS | FAIL |
| Colorblind-safe palette (no red/green only) | PASS | FAIL |
| Patterns/textures as secondary differentiator | PASS | FAIL |
| aria-label on chart container (SVG role="img") | PASS | FAIL |
| Data table alternative available | PASS | FAIL |
| Keyboard navigable (focus on data points) | PASS | FAIL |
| Screen reader descriptions for trends | PASS | FAIL |
| Tooltip accessible via keyboard (not hover-only) | PASS | FAIL |
| Text labels minimum 12px font size | PASS | FAIL |
  ...

Step 8: Dashboard Composition

When building multi-chart dashboards, apply layout principles:

DASHBOARD DESIGN:
Layout: <grid columns — e.g., 12-column grid>
Sections:
  1. <KPI row — number cards with sparklines>
  2. <Primary chart — largest, most important visualization>
  3. <Supporting charts — 2-3 smaller charts providing context>
  4. <Detail table — filterable data table for drill-down>

DASHBOARD PRINCIPLES:
  1. Most important metric is top-left (F-pattern reading)
  2. KPI cards first — give the executive summary before details
  3. Max 7 ± 2 charts per dashboard (cognitive load limit)
  ...

Step 9: Performance Optimization

Optimize chart rendering for large datasets:

PERFORMANCE STRATEGIES:
| < 1,000 points | Render all — no optimization needed |
|--|--|
| 1K - 10K points | Canvas rendering (not SVG), debounce tooltips |
| 10K - 100K points | Data aggregation, LTTB downsampling, WebGL |
| > 100K points | Server-side aggregation, WebGL (deck.gl) |

Key techniques: Canvas over SVG for > 1K points, LTTB downsampling for time series,
IntersectionObserver for lazy-loading, useMemo for data transforms, Web Workers for heavy processing.

Step 10: Validation & Delivery

Validate the visualization and produce deliverables:

VISUALIZATION VALIDATION:
| Check | Status |
|--|--|
| Chart type matches data and communication goal | PASS | FAIL |
| Data transformations produce correct output | PASS | FAIL |
| Responsive at mobile, tablet, desktop breakpoints | PASS | FAIL |
| Accessibility checklist complete (all items pass) | PASS | FAIL |
| Color palette is colorblind-safe | PASS | FAIL |
| Performance acceptable at expected data volume | PASS | FAIL |
| Tooltips show correct formatted values | PASS | FAIL |
| Axis labels and titles are clear and formatted | PASS | FAIL |
| Legend is present and correctly maps to data series | PASS | FAIL |
  ...

Produce deliverables:

VISUALIZATION COMPLETE:

Artifacts:
- Chart component: src/components/charts/<ChartName>.tsx
- Data transformer: src/utils/chart-data/<transformer>.ts
- Dashboard layout: src/pages/<dashboard>.tsx (if dashboard)
- Storybook story: src/components/charts/<ChartName>.stories.tsx
- Tests: src/components/charts/__tests__/<ChartName>.test.tsx

Validation: <PASS | NEEDS REVISION>
Chart type: <type>
Library: <library>
  ...

Commit: "chart: <component> — <chart type>, <library>, <N> data series, responsive + accessible"

Key Behaviors

# Test chart rendering and accessibility
npm run test:charts
npx storybook build --ci
npx chromatic --exit-zero-on-changes

1. Data story first, chart second. Communication goal first.
2. Accessibility not optional. Data table + colorblind-safe + screen reader.
3. Responsive by default. Works at 320px, 768px, 1440px.
4. Performance scales with data. Canvas for > 1K points.
5. Consistent dashboards. Same colors, typography, interactions.
6. No misleading visualizations. Bar charts start at 0.
7. Color is not the only channel. Patterns, labels, position too. On failure: revert with git reset --hard HEAD~1.

Flags & Options

Flag	Description
(none)	Full chart design and implementation workflow
--type <chart>	Force chart type: bar, line, scatter, heatmap, treemap, sankey, pie, area
--lib <library>	Force library: d3, chartjs, recharts, plotly, nivo, victory

HARD RULES

Never ask to continue. Loop autonomously until all charts render within targets and pass accessibility checks.

1. NEVER use pie charts for more than 5 categories. No exceptions. Use bar charts instead.
2. NEVER use 3D charts. They distort data and add no information.
3. NEVER ship without a data table alternative for screen readers.
4. NEVER start bar chart y-axis above zero unless explicitly documented with justification.
5. ALWAYS test at 320px, 768px, and 1440px before marking responsive as done.
6. ALWAYS verify colorblind safety with Chrome DevTools vision deficiency emulation.
7. git commit BEFORE verify — commit the chart component, then run visual/a11y tests.
8. TSV logging — log every chart creation:

   timestamp	chart_type	library	data_points	responsive	a11y_score	status
   

Auto-Detection

On activation, automatically detect project context without asking:

AUTO-DETECT:
1. Framework:
   ls package.json 2>/dev/null && grep -o '"react"\|"vue"\|"angular"\|"svelte"' package.json
   # Determines component style and library compatibility

2. Existing chart libraries:
   grep -r "recharts\|chart.js\|d3\|plotly\|nivo\|victory" package.json 2>/dev/null
   # Prefer existing library over introducing a new one

3. Design system:
   ls src/theme* src/styles/tokens* tailwind.config* 2>/dev/null
   # Extract color palette, font family, spacing tokens
  ...

Output Format

After each chart skill invocation, emit a structured report:

CHART BUILD REPORT:
| Charts created | <N> |
|--|--|
| Charts updated | <N> |
| Library used | <library name> |
| Data points | <N> total across all charts |
| Responsive | YES / NO |
| A11y (data table) | YES / NO |
| Colorblind-safe | YES / NO |
| Bundle impact | +<N> KB (gzipped) |
| Render time | <N> ms (largest chart) |
| Verdict | PASS | NEEDS REVISION |

Keep/Discard

KEEP if: improvement verified. DISCARD if: regression or no change. Revert discards immediately.

Stop Conditions

Stop when: target reached, budget exhausted, or >5 consecutive discards.