From Idea To Retirement Countdown: Building With An AI Coding Agent

🔍 Read the full analysis: From Idea To Retirement Countdown: Building With An AI Coding Agent on ThorstenMeyerAI.com

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Developer Thorsten Meyer says he used the AI coding agent Claude Opus 5.5 to build and publish Altersteilzeit, a free web app for counting the working days in a German partial-retirement schedule, between September 28 and October 2, 2026. The project grew from a request for a one-minute animated film into a site with a daily countdown, a narrated film, games and other planning tools, while Meyer supplied direction, made product decisions and approved releases.

Altersteilzeit is a form of partial retirement. In the block model, a person works through an active phase and then has an equally long passive phase away from work; a 4:4 arrangement, for example, pairs four years in each phase. Meyer says users enter the start date of either phase and select a model from 1:1 to 5:5. The app calculates the other date and counts working days, accounting for weekdays, the selected German state’s public holidays and leave entered by the user.

The finished app includes a daily countdown with milestones and a saying of the day, a short narrated film, and a 3D game collection. Meyer’s account describes the games as nineteen in number, while a later description of the game says it is playable in fifteen modes; the article does not explain the difference. Other features include calendar exports, a printable calendar, a bridge-day finder, badges, a team countdown and support for seven languages and five German dialects.

Meyer says all 24 commits were co-authored by Claude Opus 5.5. He reports that the agent handled coding, testing, translations, voice clips, sound effects, screenshots and deployment. The project included about 18,000 lines of JavaScript and Python and fifteen test scripts, according to Meyer. Those figures and the account of the agent’s contribution come from the developer; the published material does not provide an independent technical audit.

A Small Product Built With Agent Help

The project offers a concrete account of how a developer used an AI coding agent on a tightly scoped product, rather than a general claim about what such tools can do. Meyer describes a workflow in which the agent proposed a plan, implemented and tested features, recorded its work and deployed updates, while he reviewed the results and made decisions about the app’s purpose and style.

That division of work matters because the app was more than a countdown calculation. It combined date handling, localization, audio, 3D gameplay and public-facing legal pages. Meyer says he retained responsibility for choices such as the humor, the film’s cinematic tone, the voices and the contact details. His account suggests that faster implementation did not remove the need for human judgment or release approval. It does not, by itself, establish how the app compares with a conventionally developed product or how reliably the agent would perform on other projects.

Privacy is another stated design choice. Meyer says the site has no accounts, cookies or tracking, and that calculations run in the browser. Shared dates are placed after the “#” in a web address, which browsers do not send to the server in the ordinary request. These are the developer’s descriptions; the source account does not include an external privacy review.

From Film Request to Public App

Meyer dates the initial request to Monday, September 28, 2026. He first asked for a short animated film about the working days in an Altersteilzeit schedule. During the following five days, the project expanded to include the date calculator, game prototypes, additional languages and a public website. Meyer says the app was online by the first evening, with legal pages, and that he approved the release on Friday, October 2.

His day-by-day account describes seven languages and several games arriving early in the week, followed by badges, a bridge-day finder, more game content, narration and sound effects. He also reports a fix for an iPhone scrolling problem. On the fifth day, he approved the work and added five German dialects as language options, including voice recordings. The sequence illustrates the project’s rapid feature growth, but the account does not provide independent records of development time or a comparison with other tools.

The app turns calendar time into the structure of its games: months and weeks form a maze, while other games use working days, quarters or nights as gameplay units. Meyer says the game names were chosen to avoid other companies’ trademarks. This approach ties the entertainment features directly to the countdown rather than treating them as separate content.

“A short animated film that counts down the working days of a German Altersteilzeit in the block model.”

— Thorsten Meyer, describing his initial request

What the Account Does Not Verify

The details come from Meyer’s own account, published October 13, 2026. The source does not include an independent review of Claude Opus 5.5’s contributions, the app’s calculations, its privacy practices or its accessibility and reliability. It also does not report user numbers, ongoing maintenance plans or whether the app has been tested across different German state holiday calendars.

There is a small inconsistency in the feature description: the app is described as having nineteen 3D games, but the gameplay section says the game is playable in fifteen modes. The material does not clarify whether those numbers refer to different counts, such as games and modes, or reflect a change during development. Meyer’s reported totals for generated text and audio are likewise not accompanied by supporting documentation.

Maintenance and User Feedback

The account does not announce a future release date or a specific next feature. Since Altersteilzeit is already public, the next practical steps are likely to be continued maintenance and responses to user feedback, though Meyer has not described a schedule for either. Users can consult the live app for its current features, while questions about accuracy, privacy and support remain for the developer to address.

Any later evaluation of the project would benefit from information about how the app handles updates to public holidays, whether its date calculations have been independently checked and how it performs for users with different schedules. Meyer’s account establishes what he says was built and how he says the work was divided; it does not settle those questions.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German form of partial retirement. In the block model described by Meyer, a person works through an active phase and then spends an equal-length passive phase away from work.

What does the app calculate?

Users enter the start date of one phase and choose a schedule from 1:1 to 5:5. The app calculates the other date and counts working days, taking weekdays, selected state public holidays and entered leave into account, according to Meyer.

What did the AI coding agent do?

Meyer says Claude Opus 5.5 helped with coding, testing, translations, audio production, screenshots and deployment. He says he gave directions, made decisions and approved releases.

Is the app’s privacy design independently verified?

No independent review is included in the source account. Meyer says the app has no accounts, cookies or tracking and calculates dates in the browser, but those claims are attributed to the developer.

Source: ThorstenMeyerAI.com