---

name: code-explanation description: Explain code with ASCII diagrams, analogies, and Mermaid visualizations. Triggers: explain this code, how does this work, what does this do, explain architecture, visualize code, diagram this, help me understand

Code Explanation Skill

Explain code clearly using ASCII diagrams, real-world analogies, and Mermaid visualizations.

When to Use

• User asks "explain this code" or "what does this do"
• User wants to understand how something works
• User asks for architecture visualization
• User needs help understanding complex logic

Explanation Framework

Step 1: Quick Summary

Start with a one-sentence plain English summary:

"This function takes a list of orders, filters out cancelled ones, calculates the total, and applies any applicable discounts."

Step 2: Identify the Audience Level

Adjust explanation depth based on context:

• Beginner: Use analogies, avoid jargon, explain fundamentals
• Intermediate: Focus on patterns, design decisions, trade-offs
• Expert: Discuss edge cases, performance, alternatives

Step 3: Break Down the Logic

Use structured sections:

1. Purpose: What problem does this solve?
2. Inputs: What data comes in?
3. Process: What transformations happen?
4. Outputs: What comes out?
5. Side Effects: What else changes?

ASCII Diagram Patterns

Data Flow

Input          Process           Output
  |               |                |
  v               v                v
+------+    +-----------+    +--------+
| User | -> | Validator | -> | Result |
| Data |    | Function  |    | Object |
+------+    +-----------+    +--------+
                 |
                 v
            +----------+
            | Database |
            +----------+

Function Pipeline

[Raw Data]
     |
     v
+-------------+
| Parse JSON  |
+-------------+
     |
     v
+-------------+
| Validate    |
+-------------+
     |
   +-+-+
   |   |
   v   v
 Valid Invalid
   |     |
   v     v
+----+ +-------+
|Save| |Error  |
+----+ +-------+

Class Relationships

     +----------------+
     |   BaseClass    |
     +----------------+
     | - privateVar   |
     | + publicMethod |
     +-------+--------+
             |
     +-------+-------+
     |               |
     v               v
+----------+   +----------+
| ChildA   |   | ChildB   |
+----------+   +----------+
| + methodA|   | + methodB|
+----------+   +----------+

State Machine

         +--------+
         | START  |
         +---+----+
             |
             v
    +--------+--------+
    |                 |
    v                 v
+-------+        +--------+
| IDLE  |<------>| ACTIVE |
+---+---+        +----+---+
    |                 |
    v                 v
+-------+        +--------+
| ERROR |        | DONE   |
+-------+        +--------+

Request/Response Flow

Client                   Server                  Database
  |                        |                        |
  |  1. POST /users        |                        |
  |----------------------->|                        |
  |                        |  2. INSERT INTO users  |
  |                        |----------------------->|
  |                        |                        |
  |                        |  3. Return new ID      |
  |                        |<-----------------------|
  |  4. 201 Created        |                        |
  |<-----------------------|                        |
  |                        |                        |

Mermaid Diagram Generation

Flowchart

flowchart TD
    A[Start] --> B{Is Valid?}
    B -->|Yes| C[Process Data]
    B -->|No| D[Return Error]
    C --> E[Save to DB]
    E --> F[Send Response]
    D --> F
    F --> G[End]

Sequence Diagram

sequenceDiagram
    participant U as User
    participant A as API
    participant D as Database
    participant C as Cache

    U->>A: Request Data
    A->>C: Check Cache
    alt Cache Hit
        C-->>A: Return Cached
    else Cache Miss
        A->>D: Query Database
        D-->>A: Return Results
        A->>C: Store in Cache
    end
    A-->>U: Send Response

Class Diagram

classDiagram
    class User {
        +String id
        +String email
        +String name
        +getProfile()
        +updateSettings()
    }
    class Order {
        +String id
        +User user
        +List items
        +calculateTotal()
    }
    class Item {
        +String id
        +String name
        +Number price
    }
    User "1" --> "*" Order : places
    Order "*" --> "*" Item : contains

State Diagram

stateDiagram-v2
    [*] --> Pending
    Pending --> Processing: submit
    Processing --> Completed: success
    Processing --> Failed: error
    Failed --> Pending: retry
    Completed --> [*]

Architecture Diagram

graph TB
    subgraph Client
        A[Web App]
        B[Mobile App]
    end

    subgraph Backend
        C[API Gateway]
        D[Auth Service]
        E[User Service]
        F[Order Service]
    end

    subgraph Data
        G[(PostgreSQL)]
        H[(Redis Cache)]
        I[(S3 Storage)]
    end

    A --> C
    B --> C
    C --> D
    C --> E
    C --> F
    E --> G
    E --> H
    F --> G
    F --> I

Real-World Analogies

Common Programming Concepts

Concept	Analogy
Variable	A labeled box that stores something
Function	A recipe that takes ingredients and produces a dish
Class	A blueprint for building houses
Instance	An actual house built from the blueprint
Interface	A job contract specifying required skills
Inheritance	Children inheriting traits from parents
Callback	Leaving your phone number for a callback
Promise	An IOU note that will be fulfilled later
Cache	A sticky note reminder of frequently used info
Queue	A line at a coffee shop (FIFO)
Stack	A stack of plates (LIFO)
Hash Map	A library card catalog for quick lookups
API	A restaurant menu - shows what you can order
Database	A giant filing cabinet with organized folders
Middleware	Security checkpoints before entering a building
Event Loop	A receptionist handling one task at a time

Architecture Patterns

Pattern	Analogy
Microservices	A food court with specialized restaurants
Monolith	A single restaurant doing everything
Load Balancer	A host at a busy restaurant seating guests
Message Queue	A post office sorting and delivering mail
Circuit Breaker	A fuse box that trips to prevent damage
Pub/Sub	A newspaper subscription service

Explanation Template

## What This Code Does

{One-sentence summary}

## Visual Overview

{ASCII diagram or Mermaid diagram}

## Step-by-Step Breakdown

### 1. {First major step}
{Explanation with code snippet}

### 2. {Second major step}
{Explanation with code snippet}

## Analogy

Think of this like {real-world comparison}...

## Key Concepts

- **{Concept 1}**: {Brief explanation}
- **{Concept 2}**: {Brief explanation}

## Common Questions

**Q: Why is it done this way?**
A: {Explanation of design decision}

**Q: What could go wrong?**
A: {Edge cases and error scenarios}

Tips

1. Start simple: Give the overview before diving into details
2. Use visuals: A diagram often explains better than paragraphs
3. Relate to familiar concepts: Analogies bridge the knowledge gap
4. Show, don't just tell: Include relevant code snippets
5. Anticipate questions: Address the "why" not just the "what"