🔍 Read the full analysis: Five Days, One Retirement Countdown: A Real-World AI Coding Experiment on ThorstenMeyerAI.com
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TL;DR
Thorsten Meyer says he worked with the coding agent Claude Opus 5.5 to build Altersteilzeit, a free web app for tracking a German partial-retirement schedule, between Sept. 28 and Oct. 2, 2026. The project expanded from a short animated film into a site with a countdown, games, multilingual narration and other features; Meyer says he guided the work and approved releases.
Developer Thorsten Meyer says he built and released Altersteilzeit, a free web app for counting down to retirement, with the AI coding agent Claude Opus 5.5 over five days, from Sept. 28 to Oct. 2, 2026. What began as a request for a one-minute animated film grew into a site with a working-day countdown, a film, 3D games and multilingual audio, while Meyer directed the work and approved releases.
Meyer described the project in an account published Oct. 13 on ThorstenMeyerAI.com. The app is designed for people using Germany’s Altersteilzeit partial-retirement arrangement in the block model: a period of regular work followed by an equal-length period away from work. Users enter a start date and choose a model ranging from 1:1 to 5:5. The app calculates the corresponding dates and remaining working days, accounting for weekdays, state public holidays and entered leave.
The finished site combines that calculation with a daily display, milestones, a saying of the day, a short narrated film and games based on the user’s schedule. Meyer’s account describes 19 3D games, seven languages and five German dialects, alongside features including a team countdown, a bridge-day finder, badges and calendar exports. The source’s feature descriptions are not fully consistent: an earlier summary refers to a game with nineteen ways to play, while the day-by-day account describes fifteen modes and says twelve games were added on the third day.
Meyer says all 24 commits were co-authored by Claude Opus 5.5. He characterizes his role as describing desired features, making design choices, reviewing results and approving releases. The account also credits the agent with implementation, testing, documentation and deployment. These are the developer’s descriptions of his own project; the article does not provide an independent audit of the code, agent contributions or development timeline.
Infographic 01 · From a one-minute film to a small studio’s output
Five days, sixteen versions
One person giving directions, one AI coding agent building and testing. Every day ended with something live that anyone could open in a browser.
Mon 28 Sep
4 commits2 games1 lang.
- v1A 51-second film of both phases, with a generated soundtrack
- v2–v3Leave, real working days, humour; anyone can enter their own dates
- v4–v5Two 3D game prototypes become one game: every year is a level
- v6Online on Netlify with landing page and seven legal pages
Tue 29 Sep
4 commits7 games7 lang.
- v7Seven languages everywhere, plus the daily view
- v8Office-chair kart: the third way to play
- v9Four more games, including mini golf for the passive phase
Wed 30 Sep
5 commits19 games7 lang.
- v10Badges and six everyday features
- v11–v12Seven more games, from paper plane to sailing regatta
- v12.1Hotfix: pages scroll on iPhone again
- v13Bridge-day finder, wish list, year review, four difficulty levels, five new games
Thu 1 Oct
6 commits19 games7 lang.
- v13.1“Time for AI”: the countdown recommends an Inside AI building
- v14A narrator in seven languages: film, saying of the day, game announcer
- v14.1–14.2One voice per role and mood; iOS audio fix
- v15Sound effects for film and games
Fri 2 Oct
5 commits19 games12 lang.
- Approval“All OK, roll it all out.”
- v16Five German dialects as full languages, voices included
- v16.1Announcement in twelve languages
Source: project repository and development log, 28 Sep – 2 Oct 2026; live site altersteilzeit.netlify.app.
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Where the Developer Stayed in Control
The project offers a concrete example of how a developer says an AI coding agent contributed to a small, public-facing software release. Its value as a report is not just the feature count: Meyer describes a workflow in which the agent handled substantial implementation and production tasks, while a person supplied the concept, chose the tone and made approval decisions. That distinction matters as coding agents become part of software development, because speed alone does not show who set priorities or judged whether a result was ready.
The app also ties its core calculation to a real planning need. A countdown based on working days, regional holidays and leave can communicate a retirement schedule more precisely than a simple calendar-day counter. Yet the source does not report user numbers, independent testing, accuracy checks across German states or evidence that the app changed how people plan. The account documents one developer’s experience, not a measured comparison of AI-assisted and conventional development.
Meyer says privacy shaped the app from the start: it has no accounts, cookies or tracking, and date calculations happen in the browser. Shared dates are placed after the hash mark in a URL, which he says is not sent to the server. Those are meaningful design choices for a tool involving personal schedules, but the source offers no external privacy or security review.
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From Film Request to Full Web App
The project began on Monday, Sept. 28, when Meyer asked the agent for a short animated film about the active and passive phases of a German Altersteilzeit arrangement. In the block model, a person works as usual during the active phase and then takes an equally long passive phase. Meyer used a 4:4 model as an example and said the original aim was to make the daily countdown more entertaining.
According to his timeline, the first day brought the film, date calculations and two game prototypes that were combined into a game with a level for each year of the active phase. Work on subsequent days added translations, more games, badges, the bridge-day finder and a narrator. On the fifth day, Meyer approved the release and added German dialect versions. He says the site was online on the first evening, then continued to expand through the week.
The games use calendar time as their organizing system: for example, months and weeks map to spaces in a maze, while workdays and quarters shape other games. Meyer says the project involved about 18,000 lines of JavaScript and Python, 15 test scripts and 1,224 voice clips. These figures come from his account and have not been independently verified. The source also says the experience was built to run in the browser, including offline single-file pages.
“The interesting part is not how much an AI agent can build, but what was still left for me to do.”
— Thorsten Meyer, describing the project’s central question
What the Account Does Not Verify
The five-day schedule, commit count, code volume, tests and media-production figures are reported by Meyer; the source does not include logs, code-review findings or an independent assessment. It is also unclear how much time Meyer spent reviewing and correcting the agent’s output, how the app performs across devices, and whether the working-day calculation has been checked against every relevant state holiday calendar.
Some scope details vary within the source account. It first describes a 3D game with nineteen ways to play, then says the game has fifteen modes; the overall feature list also does not establish whether every listed feature was complete and publicly available at the time of release. No usage figures, user feedback, maintenance plan or independently reviewed privacy assessment are provided.
Maintenance and Independent Checks
The source describes Altersteilzeit as publicly available but does not announce a specific next release or development milestone. The immediate next steps for readers evaluating the project are to inspect the live app and its published legal and privacy information, and to check whether the date calculations match their own state, leave balance and employment arrangement.
Meyer’s account leaves open how the app will be maintained as holiday calendars, browser behavior and the underlying AI coding tools change. Any future claims about reliability, privacy or time saved would be stronger with documented testing and user evidence. For now, the next confirmed development is not a new feature announcement but the publication of his account on Oct. 13, 2026.
Key Questions
What is Altersteilzeit?
Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a person works during an active phase and then has an equally long passive phase away from work.
What does the app calculate?
Users enter a start date and choose a schedule model from 1:1 to 5:5. Meyer says the app calculates the other phase’s date and counts working days, factoring in weekdays, public holidays in the selected German state and leave entered by the user.
How long did the project take?
Meyer says development ran from Sept. 28 through Oct. 2, 2026. He reports that the app was online on the first evening and that features continued to be added during the five-day period.
What did the AI coding agent do?
According to Meyer, Claude Opus 5.5 helped build features, write and test code, produce translations and audio assets, and support deployment. Meyer says he supplied direction, made design decisions, reviewed the results and approved releases; the account has not been independently audited.
Is the app’s privacy approach independently verified?
No independent privacy review is included in the source. Meyer says the app has no accounts, cookies or tracking and performs calculations in the browser, but those statements should be understood as the developer’s description.
Source: ThorstenMeyerAI.com
