playbook/superpowers/tests/subagent-driven-dev/go-fractals/design.md

Go Fractals CLI - Design

Overview

A command-line tool that generates ASCII art fractals. Supports two fractal types with configurable output.

Usage

# Sierpinski triangle
fractals sierpinski --size 32 --depth 5

# Mandelbrot set
fractals mandelbrot --width 80 --height 24 --iterations 100

# Custom character
fractals sierpinski --size 16 --char '#'

# Help
fractals --help
fractals sierpinski --help

Commands

sierpinski

Generates a Sierpinski triangle using recursive subdivision.

Flags:

• --size (default: 32) - Width of the triangle base in characters
• --depth (default: 5) - Recursion depth
• --char (default: '*') - Character to use for filled points

Output: Triangle printed to stdout, one line per row.

mandelbrot

Renders the Mandelbrot set as ASCII art. Maps iteration count to characters.

Flags:

• --width (default: 80) - Output width in characters
• --height (default: 24) - Output height in characters
• --iterations (default: 100) - Maximum iterations for escape calculation
• --char (default: gradient) - Single character, or omit for gradient " .:-=+*#%@"

Output: Rectangle printed to stdout.

Architecture

cmd/
  fractals/
    main.go           # Entry point, CLI setup
internal/
  sierpinski/
    sierpinski.go     # Algorithm
    sierpinski_test.go
  mandelbrot/
    mandelbrot.go     # Algorithm
    mandelbrot_test.go
  cli/
    root.go           # Root command, help
    sierpinski.go     # Sierpinski subcommand
    mandelbrot.go     # Mandelbrot subcommand

Dependencies

• Go 1.21+
• github.com/spf13/cobra for CLI

Acceptance Criteria

1. fractals --help shows usage
2. fractals sierpinski outputs a recognizable triangle
3. fractals mandelbrot outputs a recognizable Mandelbrot set
4. --size, --width, --height, --depth, --iterations flags work
5. --char customizes output character
6. Invalid inputs produce clear error messages
7. All tests pass