Try it first. Then build it yourself.
In “Building Platforms with AI Agents”, you build a small marketplace with Claude Code or Codex. Try a small part of it here and see how it works.
Who sees what? Try it out.
Lea needs help with her bicycle workshop. Mara wants to send her an offer. Start as Mara, then switch perspectives.
Mara is preparing an offer.
One click creates a draft, not a submission.
What if the reading rule vanished?
Only in this simulation: let an outsider see the text and observe the difference. The download remains unchanged.
Start a draft, switch to Tobias and suspend the reading rule here.
Technical view
This demo illustrates a browser-side rule. Real permissions must be enforced on the server and, where appropriate, in the database. In chapter 12, you remove a condition in a local test project and see the matching test fail.
Browser simulation · fictional data · no sign-in. Nothing is saved or sent.
Another glimpse: from draft to replyFive real browser captures show how a private proposal becomes a shared workflow. Move through them at your own pace.
Watch one real browser walkthrough.
View 1 / 5
Mara starts. Nobody else reads along.
Select Mara, then start a draft. There is text, but no message to Lea yet. Writing and submitting are different actions.
About the capture
Captured on 7 September 2026 in the in-app browser at 1280 × 960 pixels. Synthetic accounts and server-side in-memory state; no real sign-in or persistent database. This is an image sequence, not a video recording.
One click becomes a whole project.
The book starts with a button. Step by step, it grows into a marketplace with sign-in, saved proposals and tests. Learn to guide your coding agent, check its work and apply the techniques to your own idea.
Reading along? Start the companion project here.
The free English starter includes the learning page, completed references and English project guides. Access to a coding agent is required and is not included.
Open the starter
Download and unpack the starter, then open the auftragsplatz folder in Codex or Claude Code.
Let the agent set it up
Ask: “Read START-HERE.md, set up the project and open the learning page.” You provide any required approvals yourself.
Build your first button
The learning page is deliberately almost empty. Chapter 3 guides you through your first feature; sign-in and a database follow later.
English 0.5.3-en.1 · same learning path as German 0.5.3. Includes a guide to labels in the book’s German screenshots.
Prefer the German starter?Fixed starting point · 0.5.3-en.1
- Included
- Empty learning page, completed references, and role simulation
- Data
- fully synthetic
- SHA-256
- 12eaaf6ac08eed7c41342fda33eefae6ef91b2d44263d9654d790ed87e367f00