ascii-visualizer

ASCII Visualizer

Consistent, readable ASCII diagrams for architecture, workflows, file trees, and data visualizations. All output renders correctly in monospace terminals without external tools.

Core principle: Encode information into structure, not decoration. Every diagram element should communicate something meaningful.

Box-Drawing Character Reference

This block intentionally shows multiple sets together as a key. Authors should use ONE set per real diagram; the single-set lint rule enforces this on production diagrams.

<!-- ascii-lint-disable: single-set,single-arrow-style,density-min -->

default:   ┌─┐ │ └─┘  ├─┤ ┬ ┴ ┼
emphasis:  ┏━┓ ┃ ┗━┛  ┣━┫ ┳ ┻ ╋
title:     ╔═╗ ║ ╚═╝  ╠═╣ ╦ ╩ ╬
soft:      ╭─╮ │ ╰─╯
portable:  +-+ | +-+  +-+ + + +
Arrows:    → ← ↑ ↓ ─> <─ ──> <──
Blocks:    █ ▓ ░ ▏▎▍▌▋▊▉
Status:    ● ○ ✓ ✗ ⚠ ◆ ◇ ▶ ▷  ↑↓→ ▓▒░  (closed-set vocab — see rules)

Set Conventions (D8: intent-driven naming)

Tokens live in tokens.json. Names describe USE not APPEARANCE.

Set	Characters	Use For
default ─│	Normal boxes and connectors	Most diagrams
emphasis ━┃	Headers, focus, draw the eye	Key components, outer frames
title ═║	Document titles	§0-style banners only
soft ╭╮╰╯ ─│	Status cards, ambient UI	Diff blocks
portable +-|	NO_COLOR / CI / bare TTY	Fallback

Rename codemod (D8): old light/heavy/double/rounded/ascii-fallback → new names above. Old names accepted with warning for one minor release.

Status Glyph Vocabulary

Closed-set v1 of 11 semantic glyphs (●○✓✗⚠◆◇▶▷ ↑↓→ ▓▒░). Single source of truth — see rules/status-glyph-vocabulary.md. Add-a-glyph process in CONTRIBUTING.md.

Diagram Patterns

Architecture Diagrams

┌──────────────┐      ┌──────────────┐
│   Frontend   │─────>│   Backend    │
│   React 19   │      │   FastAPI    │
└──────────────┘      └───────┬──────┘
                              │
                              v
                      ┌──────────────┐
                      │  PostgreSQL  │
                      └──────────────┘

File Trees with Annotations

src/
├── api/
│   ├── routes.py          [M] +45 -12    !! high-traffic path
│   └── schemas.py         [M] +20 -5
├── services/
│   └── billing.py         [A] +180       ** new file
└── tests/
    └── test_billing.py    [A] +120       ** new file

Legend: [A]dd [M]odify [D]elete  !! Risk  ** New

Progress Bars

[████████░░] 80% Complete
+ Design    (2 days)
+ Backend   (5 days)
~ Frontend  (3 days)
- Testing   (pending)

Swimlane / Timeline Diagrams

Backend  ===[Schema]======[API]===========================[Deploy]====>
                |            |                                ^
                |            +------blocks------+             |
                |                               |             |
Frontend ------[Wait]--------[Components]=======[Integration]=+

=== Active work   --- Blocked/waiting   | Dependency

Blast Radius (Concentric Rings)

            Ring 3: Tests (8 files)
       +-------------------------------+
       |    Ring 2: Transitive (5)      |
       |   +------------------------+   |
       |   |  Ring 1: Direct (3)     |   |
       |   |   +--------------+      |   |
       |   |   | CHANGED FILE |      |   |
       |   |   +--------------+      |   |
       |   +------------------------+   |
       +-------------------------------+

Comparison Tables

BEFORE                          AFTER
┌────────────┐                  ┌────────────┐
│  Monolith  │                  │  Service A │──┐
│  (all-in-1)│                  └────────────┘  │  ┌──────────┐
└────────────┘                  ┌────────────┐  ├─>│  Shared  │
                                │  Service B │──┘  │  Queue   │
                                └────────────┘     └──────────┘

Reversibility Timeline

Phase 1  [================]  FULLY REVERSIBLE    (add column)
Phase 2  [================]  FULLY REVERSIBLE    (new endpoint)
Phase 3  [============....]  PARTIALLY           (backfill)
              --- POINT OF NO RETURN ---
Phase 4  [........????????]  IRREVERSIBLE        (drop column)

Key Rules

Rule	Description
Font	Always monospace — box-drawing requires fixed-width
Weight	Standard for normal, Heavy for emphasis, Double for titles
Arrows	─>, ──>, or │ with v/^ for direction
Alignment	Right-pad labels to match column widths
Annotations	!! for risk, ** for new, [A/M/D] for change type
Width	Keep under 80 chars for terminal compatibility
Nesting	Max 3 levels of box nesting before readability degrades

When to Use Each Pattern

Pattern	Use Case
Layered boxes	System architecture, deployment topology
Concentric rings	Blast radius, impact analysis
Timeline bars	Reversibility, migration phases
Swimlanes	Execution order, parallel work streams
Annotated trees	File change manifests, directory structures
Comparison tables	Cross-layer consistency, before/after
Progress bars	Status tracking, completion metrics

Related Skills

• brainstorm — Design exploration where diagrams communicate ideas
• architecture-patterns — System architecture that benefits from ASCII diagrams
• code-review-playbook — Review comments with inline diagrams