csharpfritz/architecture-documentation

Context

When a project involves complex spatial logic (coordinate systems, layout algorithms, size constraints) or technical constraints (rate limits, API boundaries), create two complementary reference documents:

1. Architecture diagram (educational) — visual explanations that help contributors understand the math and logic
2. Constraints documentation (prescriptive) — authoritative rules that enforce consistency

This skill applies when:

• Code uses non-obvious coordinate calculations or spatial algorithms
• There are hard technical limits (API rates, world boundaries, size caps)
• Multiple services/features must coordinate on shared conventions (e.g., all features use same Y-level convention)
• New contributors need to understand "why these specific numbers"

Patterns

Two-Document Pattern

Document 1: Visual Architecture (docs/architecture-diagram.md)

• ASCII art or mermaid diagrams showing spatial relationships
• Step-by-step coordinate calculation examples with real numbers
• Cross-sections showing different perspectives (top-down, side view)
• Example scenarios ("4-resource village coordinates")
• "Why" explanations: design rationale, trade-offs

Document 2: Constraints Reference (docs/[domain]-constraints.md)

• Table of contents for quick lookup
• Prescriptive rules in "must/never" language
• Exact constants and formulas (with source file references)
• Critical warnings highlighted with ⚠️ emoji
• Performance characteristics and scaling limits
• Anti-patterns section ("❌ Wrong: ... ✅ Correct: ...")

Structure Patterns

Both documents should include:

• Source file references at the end — link to authoritative code
• Cross-references between docs (architecture → constraints, constraints → architecture)
• Version-specific info (e.g., "BaseY=-60 for superflat worlds")
• Scaling limits explicitly documented

Content Organization

Architecture diagrams:

1. Big picture first (full coordinate system)
2. Zoom into specifics (individual structure footprints)
3. Worked examples with real numbers
4. Edge cases and scale limits last

Constraints:

1. Table of contents (long document, need quick lookup)
2. Foundational conventions first (coordinate system)
3. Building blocks next (structures, sizes)
4. Derived rules after (paths, fences — depend on structures)
5. System-level limits last (scale, performance)

Examples

ASCII Art for Y-Level Breakdown

Y=-59:  Air (player walking level)
        ↑ Players walk here
        │
Y=-60:  █████████████████████  ← BaseY (grass block surface)
        │                        Structures place floors here

Why this works: Visual hierarchy shows relationships. Annotations explain purpose, not just labels.

Coordinate Calculation Example

col = index % 2           // Alternates 0, 1, 0, 1, ...
row = index / 2           // Increments every 2 resources: 0, 0, 1, 1, 2, 2, ...
x = BaseX + (col × 10)    // Result: 10, 20, 10, 20, 10, 20, ...

Why this works: Formula + concrete results + inline comments. Reader sees pattern immediately.

Critical Rule Documentation

### ⚠️ Critical Y-Level Rules

1. **Never place fences at `BaseY + 1`** — they will float one block above the ground.
2. **Paths must be at `BaseY - 1`** with grass cleared at `BaseY` — this makes them flush with the surrounding terrain.

Why this works: Emoji draws attention. "Never" is unambiguous. Explanation shows consequence of violation.

Performance Constraint Table

| Operation | Command Count | Estimated Time (at 10 cmd/sec) |
|-----------|---------------|--------------------------------|
| Single structure | ~15-20 commands | 1.5-2 seconds |
| 50-resource village | ~800-900 commands | 80-90 seconds |

Why this works: Concrete numbers. Shows scaling behavior. Helps users understand cost.

Anti-Patterns

❌ Single monolithic document — hard to navigate, mixes "how it works" with "how to use it"

❌ Diagrams without numbers — "structures are spaced apart" is vague; "Spacing=10 blocks center-to-center" is precise

❌ Constants without source references — reader can't verify or update; always cite source file and line

❌ Rules without rationale — "Don't place fences at Y+1" → why? Add consequence: "they will float in the air"

❌ Examples without scaling limits — show 4-resource village working fine, hide that 50+ resources break

❌ Missing cross-references — constraints doc should point to architecture doc for visual explanations

❌ Stale examples — if constants change in code, docs break. Use grep to verify constants match.