Five Days, Sixteen Versions, Nineteen Games: What I Learned Building A Retirement Countdown With An AI Coding Agent

🔍 Read the full analysis: Five Days, Sixteen Versions, Nineteen Games: What I Learned Building A Retirement Countdown With An AI Coding Agent on ThorstenMeyerAI.com

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Thorsten Meyer says he and an AI coding agent built Altersteilzeit, a free web app for people counting down a German partial-retirement schedule, over five days from September 28 to October 2, 2026. What began as a request for a one-minute film became a site with a daily working-day countdown, a narrated film and 19 3D games, according to Meyer’s October 13 account.

Meyer describes the app as a tool for Germany’s Altersteilzeit block model, in which a person works their regular schedule during an active phase and is then released from work for a matching passive phase. Users enter a start date and choose a model from 1:1 to 5:5. The app then calculates the other phase and counts working days, accounting for weekdays, public holidays in the selected German federal state and entered leave, Meyer writes.

The site brings the countdown together with a daily saying, milestones, a progress display and optional features such as calendar exports, a printable calendar and a bridge-day finder. Its film depicts the shift from an office setting to scenes of the sea and sunrise. The games map parts of the calendar to play: in one example, Meyer says, a game’s columns represent months and its cells represent weeks. He describes 19 games, although his account also refers to the game being playable in 15 modes; it does not explain the difference between a game and a mode.

Meyer says all 24 commits were co-authored by Claude Opus 5.5 acting as a coding agent. He says the agent wrote code, ran tests, documented changes and deployed features, while he set the concept and tone, made decisions about content and voices, and approved releases. The account reports about 18,000 lines of JavaScript and Python, 15 test scripts and 1,224 voice clips across 12 languages. These are figures reported by Meyer; the article does not independently verify them.

Where the Agent’s Work Ended

Meyer’s account offers a specific example of how an AI coding agent can contribute to a small software project: not just generating a prototype, but assisting with features, testing, localization, audio production and deployment. The project’s reported pace is striking, but the account is a first-person description, not an independent evaluation of the agent’s code quality, the app’s reach or how much human work was required.

The division of labor is part of the story. Meyer says he chose the film’s tone and the app’s image of retirement as time by the sea, selected dialects and voices, and made the final approval decisions. That distinction matters to readers evaluating claims about AI-assisted development: the account describes the agent as carrying out a broad set of production tasks, while a person remained responsible for the product’s purpose and release decisions.

The app also addresses a practical, time-sensitive use case. Its countdown depends on a user’s work arrangement, location, holidays and leave, rather than a generic calendar. Meyer says calculations happen in the browser and that the site has no accounts, cookies or tracking. Those are privacy design claims in his account; readers should consult the site’s own policies and implementation to assess how the service handles data.

From Film Request to Countdown

The project began on Monday, September 28, when Meyer asked the coding agent for a short animated film counting down working days in an Altersteilzeit schedule. By the end of that day, he says, the project was online with custom dates, working-day calculations, early game prototypes and legal pages. The daily view and additional games followed over the next several days.

Meyer’s day-by-day account says the team added seven languages and more game elements on the second day, then badges, further games, a bridge-day finder and an iPhone scrolling fix on the third. A narrator and sound effects came on day four. On Friday, October 2, Meyer says he approved the release and added five German dialects as language options with voices. His account says the finished experience offers seven languages and five dialects, and separately reports voice production across 12 languages.

Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a worker completes an active phase followed by an equally long passive phase; a 4:4 model, for example, pairs four years of work with four years away from work. The app is aimed at making the remaining working days and upcoming milestones easier to track.

“It started as a one-minute film.”

— Thorsten Meyer, describing the project’s starting point

What the Account Does Not Verify

Meyer’s account is a firsthand project description. It does not provide an independent review of the app, the agent’s contributions, the reported development totals or the accuracy of the working-day calculations across individual users’ circumstances. The site’s current availability and user numbers are also not established by the account.

Some details need clarification. Meyer refers to 19 games and also says the game is playable in 15 modes, without specifying how those terms relate. He reports seven languages and five dialects, while also describing 1,224 voice clips as 102 per language across 12 languages. The account does not list all language categories or explain that count. It also does not detail how the app handles every possible employment agreement or regional holiday rule.

The App’s Use After Launch

Meyer’s account says he approved the public release on October 2, 2026. It does not announce a later release date, roadmap or planned feature set. The next development milestone, if any, has not been stated in the source material.

For users, the immediate next step is to enter their phase start date and model, then check the results against their own employment arrangements, leave and applicable state holidays. The app’s calculations and privacy practices are presented by Meyer; users with unusual schedules or questions about their rights may need to verify those details with an employer or an appropriate adviser.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a worker has an active phase followed by a passive phase of the same length.

What does the Altersteilzeit app do?

Users enter a phase start date and a model, from 1:1 to 5:5. The app displays a working-day countdown and milestones, and also offers a film, games and calendar-related tools, according to Meyer.

How long did development take?

Meyer says work ran from September 28 to October 2, 2026, with the public release approved on the fifth day.

What did the AI coding agent do?

Meyer says Claude Opus 5.5 helped write and test code, document changes, produce text and audio assets, and deploy the app. He says he set the direction, made product decisions and approved releases.

Is the app’s privacy setup independently verified?

No independent verification is included in Meyer’s account. He says the app has no accounts, cookies or tracking and performs calculations in the browser; readers would need to review the site and its policies for further confirmation.

Source: ThorstenMeyerAI.com