Show HN：Agentlearn – AI 代理基礎互動課程

I built agentlearn after noticing that most AI agent tutorials focus on frameworks (LangChain, CrewAI) rather than fundamentals. The result is developers who can copy-paste code but struggle when things break.

This is a free, interactive course covering:

The Agent Loop - Why loops matter (think vs. act vs. observe)
Context Engineering - The real skill behind "prompt engineering"
Tools & Function Calling - Bridging text generation to real actions
Memory Systems - Short-term vs. long-term, vector DBs
Protocols - MCP, A2A, and the emerging standards
Production Patterns - Error handling, cost optimization, observability
Each concept has runnable code sandboxes you can step through. The design is intentionally "hand-drawn" to feel less intimidating than typical technical docs.

Tech stack: Vanilla JS + Vite, no framework.

Why no framework? Because understanding fundamentals means understanding what frameworks abstract away. Once you get the core loop, you can use any framework—or build your own.

Feedback welcome! Especially interested in what topics are missing.