Step into real engineering systems. Assemble, modify, and break them locally — guided, but you build it.
Playgrounds →
This platform drops you into production-like codebases and architectures. You work locally, make decisions, and see the consequences — no cloud sandboxes, no magic abstractions.
Start building →This is not a tutorial platform. It's a place to practice engineering decisions inside real systems.
Unlock Full Experience
Build real systems locally. Follow guidance at first. Take ownership over time.
You start with full guidance and reference solutions. As you progress, hints fade and responsibility shifts to you.
No cloud dependencies. No expired access. The code stays on your machine.
No simulations. No cloud sandboxes. Build and run everything on your laptop.
You assemble components, explore trade-offs, and debug failure modes — with guidance, reference solutions, and responsibility.
You start with guided assembly and full reference solutions to understand the system deeply.
Later, guidance steps back — and responsibility moves to you.
Use VS Code, Vim, or any editor you prefer.
Working in your real development environment builds the same workflows and habits you'll use in practice.
The reference project syncs to your local folder automatically.
Compare your code with the reference implementation, inspect differences, and learn by reconstructing it yourself.
See exactly what changes at each step.
Every modification is shown as a clear diff, with explanations for why it matters.
Navigate systems, inspect code, and track your progress
without leaving your local workflow.
Every playground leads to a finished application you can run, inspect, and extend locally.
Not fragments, not demos — complete systems with structure, state, and behavior.
Ready-to-use prompts for AI coding assistants.
Recreate each step using Claude, Cursor, or your preferred tool — if you want shortcuts.
Learn in your native language.
Playgrounds will be available in English, Spanish, German, French, and more.
The AI asks questions, highlights weak assumptions,
and challenges your decisions — focusing on your reasoning, not replacing it.
Experience the playground interface: navigate through systems, inspect code with syntax highlighting, and track your decisions — all while staying in your local workflow.
The interface syncs with your local project, showing you exactly what changes at each step.
Enter playground →
Engineering notes, new playgrounds, and platform evolution.
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