Diagram Generator

Design System

Color Palette

Semantic colors for component categories:

For flowcharts and sequence diagrams, assign colors by role (actor, decision, process) rather than by technology.

Typography

Use embedded SVG @font-face or system monospace fallback:

<style>
  @import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;500;600;700&amp;display=swap');
  text { font-family: 'JetBrains Mono', 'SF Mono', 'Cascadia Code', monospace; }
</style>

Font sizes by role:

• Title: 16px, weight 700
• Component name: 11-12px, weight 600
• Sublabel / description: 9px, weight 400, color #94a3b8
• Annotation / note: 8px, weight 400
• Tiny label (on arrows): 7-8px

Core Visual Elements

Background: #0f172a (slate-900) with subtle grid:

<defs>
  <pattern id="grid" width="40" height="40" patternUnits="userSpaceOnUse">
    <path d="M 40 0 L 0 0 0 40" fill="none" stroke="#1e293b" stroke-width="0.5"/>
  </pattern>
</defs>
<rect width="100%" height="100%" fill="#0f172a"/>
<rect width="100%" height="100%" fill="url(#grid)"/>

Arrowhead marker (standard):

<marker id="arrow" markerWidth="10" markerHeight="7" refX="9" refY="3.5" orient="auto">
  <polygon points="0 0, 10 3.5, 0 7" fill="#64748b"/>
</marker>

Arrowhead marker (colored) — create per-color as needed:

<marker id="arrow-cyan" markerWidth="10" markerHeight="7" refX="9" refY="3.5" orient="auto">
  <polygon points="0 0, 10 3.5, 0 7" fill="#22d3ee"/>
</marker>

Open arrowhead (for async/return messages):

<marker id="arrow-open" markerWidth="10" markerHeight="7" refX="9" refY="3.5" orient="auto">
  <polyline points="0 0, 10 3.5, 0 7" fill="none" stroke="#64748b" stroke-width="1.5"/>
</marker>

SVG Structure & Layering

Draw elements in this order to get correct z-ordering (SVG paints back-to-front):

1. Background fill + grid pattern
2. Region/group boundaries (dashed outlines)
3. Connection arrows and lines
4. Opaque masking rects (same position as component boxes, fill="#0f172a")
5. Component boxes (semi-transparent fill + stroke)
6. Text labels
7. Legend (bottom-right or bottom area, outside all boundaries)
8. Title block (top-left)

The opaque masking rect trick is essential — semi-transparent component fills will show arrows underneath without it:

<!-- Mask layer: opaque background to hide arrows -->
<rect x="100" y="100" width="160" height="60" rx="6" fill="#0f172a"/>
<!-- Visual layer: styled component -->
<rect x="100" y="100" width="160" height="60" rx="6" fill="rgba(8,51,68,0.4)" stroke="#22d3ee" stroke-width="1.5"/>
<text x="180" y="125" fill="white" font-size="11" font-weight="600" text-anchor="middle">API Gateway</text>
<text x="180" y="141" fill="#94a3b8" font-size="9" text-anchor="middle">Kong / Nginx</text>

Spacing Rules

These prevent overlapping — follow them strictly:

• Component box height: 50-70px (standard), 80-120px (large/complex)
• Minimum gap between components: 40px vertical, 30px horizontal
• Arrow label clearance: 10px from any box edge
• Region boundary padding: 20px inside edges around contained components
• Legend placement: At least 20px below the lowest diagram element
• Title block: 20px from top-left, outside diagram content area
• viewBox: Always extend to fit all content + 30px padding on all sides

Component Patterns

Standard box (service/process):

<rect x="X" y="Y" width="160" height="60" rx="6" fill="#0f172a"/>
<rect x="X" y="Y" width="160" height="60" rx="6" fill="FILL" stroke="STROKE" stroke-width="1.5"/>
<text x="CX" y="Y+24" fill="white" font-size="11" font-weight="600" text-anchor="middle">Name</text>
<text x="CX" y="Y+40" fill="#94a3b8" font-size="9" text-anchor="middle">description</text>

Decision diamond (flowchart):

<g transform="translate(CX, CY)">
  <polygon points="0,-35 50,0 0,35 -50,0" fill="#0f172a"/>
  <polygon points="0,-35 50,0 0,35 -50,0" fill="rgba(120,53,15,0.3)" stroke="#fbbf24" stroke-width="1.5"/>
  <text y="4" fill="white" font-size="10" font-weight="600" text-anchor="middle">Condition?</text>
</g>

Database cylinder:

<g transform="translate(X, Y)">
  <rect x="0" y="10" width="120" height="50" rx="2" fill="#0f172a"/>
  <ellipse cx="60" cy="10" rx="60" ry="12" fill="#0f172a"/>
  <ellipse cx="60" cy="60" rx="60" ry="12" fill="#0f172a"/>
  <rect x="0" y="10" width="120" height="50" fill="rgba(76,29,149,0.4)"/>
  <ellipse cx="60" cy="10" rx="60" ry="12" fill="rgba(76,29,149,0.4)" stroke="#a78bfa" stroke-width="1.5"/>
  <ellipse cx="60" cy="60" rx="60" ry="12" fill="rgba(76,29,149,0.4)" stroke="#a78bfa" stroke-width="1.5"/>
  <line x1="0" y1="10" x2="0" y2="60" stroke="#a78bfa" stroke-width="1.5"/>
  <line x1="120" y1="10" x2="120" y2="60" stroke="#a78bfa" stroke-width="1.5"/>
  <text x="60" y="40" fill="white" font-size="11" font-weight="600" text-anchor="middle">PostgreSQL</text>
</g>

Region boundary:

<rect x="X" y="Y" width="W" height="H" rx="12" fill="none" stroke="#fbbf24" stroke-width="1" stroke-dasharray="8,4"/>
<text x="X+12" y="Y+16" fill="#fbbf24" font-size="9" font-weight="600">AWS us-east-1</text>

Security group:

<rect x="X" y="Y" width="W" height="H" rx="8" fill="none" stroke="#fb7185" stroke-width="1" stroke-dasharray="4,4"/>
<text x="X+10" y="Y+14" fill="#fb7185" font-size="8" font-weight="500">VPC / Security Group</text>

Type-Specific Layout Guidance

Determine this SKILL.md file's directory path as {baseDir}. Read the reference file for the specific diagram type before starting layout. Reference files are located at {baseDir}/references/ and contain detailed layout algorithms and examples.

Architecture Diagrams

→ Read {baseDir}/references/architecture.md

Key points: left-to-right or top-to-bottom data flow. Group related services in region boundaries. Use buses/connectors between layers. Place databases at the bottom or right.

Flowcharts

→ Read {baseDir}/references/flowchart.md

Key points: top-to-bottom primary flow. Diamonds for decisions with Yes/No labels on exit arrows. Rounded rectangles for start/end. Use the Highlight color for the happy path.

Sequence Diagrams

→ Read {baseDir}/references/sequence.md

Key points: actors as boxes at top, vertical dashed lifelines, horizontal arrows for messages (solid=sync, dashed=return). Time flows downward. Activation bars show processing. Number messages if complex.

Structural Diagrams

→ Read {baseDir}/references/structural.md

Key points: compartmented boxes (name / attributes / methods for class diagrams). Relationship lines: solid with filled diamond=composition, solid with empty diamond=aggregation, dashed arrow=dependency, solid triangle=inheritance.

Mind Maps

Free-form radiating layout from a central concept. Use organic curves (<path> with cubic beziers) for branches. Vary branch colors using the palette. Larger font for central node, decreasing as you go outward.

Timelines

Horizontal or vertical axis line. Event markers as circles or diamonds on the axis. Description text offset to alternating sides to avoid overlap. Use color to categorize event types.

State Machines

Rounded-rect states with double-border for composite states. Filled circle for initial state, bullseye for final state. Curved arrows for self-transitions. Label all transitions with event [guard] / action format.

Output Rules

1. Output a single .svg file — no external dependencies except the Google Fonts import
2. Set viewBox to fit all content with 30px padding; do NOT set fixed width/height attributes (let the SVG scale responsively)
3. Include xmlns="http://www.w3.org/2000/svg" on the root <svg> element
4. Put all <style>, <defs>, markers, and patterns at the top of the SVG
5. Use text-anchor="middle" for centered labels; ensure text doesn't overflow boxes
6. Chinese text support: When labels contain Chinese characters, use font-family: 'JetBrains Mono', 'Noto Sans SC', 'PingFang SC', sans-serif' and increase box widths — CJK characters are wider
7. Save location: If the input is a file, save to {inputFileDir}/diagram/. Otherwise save to {projectDir}/diagram/{topic-slug}/. Create the directory if it doesn't exist

Script

Determine this SKILL.md file's directory path as {baseDir}. Script path: {baseDir}/scripts/main.ts.

Resolve ${BUN_X} runtime: if bun installed → bun; if npx available → npx -y bun; else suggest installing bun.

SVG → @2x PNG

After saving the SVG, convert it to a @2x PNG:

${BUN_X} {baseDir}/scripts/main.ts <svg-path> [options]

Options:

• -s, --scale <n> — Scale factor (default: 2)
• -o, --output <path> — Custom output path (default: <input>@2x.png)
• --json — JSON output

Process

1. Identify the diagram type from the user's request
2. Read the relevant reference file if one exists for that type
3. Plan the layout: list all components, determine grouping and flow direction, calculate positions
4. Write the SVG following the layering order above
5. Verify spacing rules — no overlaps, legends outside boundaries, viewBox large enough
6. Save the SVG file
7. Run ${BUN_X} {baseDir}/scripts/main.ts <svg-path> to generate @2x PNG
8. Present both files to the user