yuangjay Deep Learn — Programming & Software Engineering
Goal
Reach L4 mastery: build it, break it, explain it, extend it.
Phase 0 — Anchor Project
Before reading a single line of docs, pick a micro-project that requires the concept:
| Concept | Suggested anchor project |
|---|---|
| Closures | Build a function factory (e.g. multiplier generator) |
| Async/await | Build a concurrent HTTP fetcher |
| Design patterns | Refactor a messy codebase using the pattern |
| Recursion | Build a tree/graph traversal from scratch |
| Decorators | Build a timing + retry decorator |
Rule: The project must be chosen before studying. Learning happens through building.
Phase 1 — L1: Surface (15 min max)
- Read the definition — one source only (official docs preferred).
- Answer in your own words:
- What problem does this concept solve?
- What did people do BEFORE this existed?
- Write a 1-sentence summary without looking.
✅ Gate: Can you define it without the source open?
Phase 2 — L2: Mechanism (30–60 min)
- Trace through how it works step by step:
- For functions/algorithms: trace with a concrete example (pen and paper or whiteboard)
- For patterns: draw the class/module diagram
- For language features: look at the bytecode/AST if possible
- Write down the rules:
- When is this evaluated?
- What happens in memory?
- What are the edge cases?
- Find one thing that surprises you — research why.
✅ Gate: Can you draw or write a step-by-step walkthrough from memory?
Phase 3 — L3: Application (1–3 hours)
- Build the anchor project from Phase 0 — no copy-paste.
- Deliberately make it break:
- What inputs cause unexpected behaviour?
- What happens at the boundary conditions?
- Read one real-world usage in an open-source project.
- Refactor your project using what you learned.
✅ Gate: Does working code exist that you wrote from scratch?
Phase 4 — L4: Mastery
- Compare: How does this compare to alternatives? Why would you choose each?
- Extend: Add one feature that wasn't in the original anchor project.
- Teach: Write a 200-word explanation for a junior developer.
- Break on purpose: Find a real bug or footgun caused by misuse of this concept.
✅ Gate: Feynman test — explain it out loud in plain English without notes.
Active Recall Prompts (ask yourself after every phase)
- What is the core mechanism in one sentence?
- What problem does this solve that something simpler couldn't?
- Write the minimal working example from memory.
- Where would a beginner go wrong with this?
Spaced Repetition Schedule
| Day | Prompt |
|---|---|
| +1 | Rebuild the anchor project from scratch without looking |
| +3 | Explain it to someone (or write a blog post outline) |
| +7 | Find a real bug in someone else's code caused by this |
| +30 | Review: what has changed in your understanding? |
Examples
learn how Python closures work deeply, step by stepI want to really understand async/await, teach me with a projectexplain the observer design pattern, then help me build something with it