[No Registration/Free] The Story of How a Working Tax Accountant Created a 'Full-Scale M&A Simulation Game' with AI and Got Trapped in a Hell of Balance Adjustments

(This article was produced with the help of Claude and Gemini)

What kind of game is it? (How to play in 60 seconds)

1. As the operator of a holding company, you start by choosing a group name (holdings name) and your core business (from 10 industries). That's it. No account registration or installation required.

2. While watching the real-time stock price chart, find undervalued companies and acquire them. If you lack cash, you can issue your own shares and use them as currency to swallow up the other party—you can also use stock-for-stock M&A.

3. When an event pops up,time stops and you are forced to make a decision. Buy, sell out, or... get involved in a shady deal.

4. About 20 years of management.The ending you reach changes depending on how you proceed.

You can finish it in a few minutes during your spare time, or immerse yourself in building an empire.

Originality — An M&A game that intentionally breaks the 'violence of scale'

While there are many management simulations, what I was particular about in this game was 'how to break the "snowball" effect where you get stronger the more you buy'.

In these types of games, once you take the lead in the early stages, you usually accumulate an advantage like a snowball and tend to run away with the win.

I broke that using the "brakes" that actually exist in real-world capitalism (of course, I haven't incorporated all the diverse regulations that exist in reality).

1. Antitrust

If you hold too many companies under your umbrella, monopolize the same industry, or buy them up too quickly, the authorities will send you a corrective order (fine + forced divestiture of subsidiaries). Moreover, this is applied equally to rival funds.

Therefore, even if the group grows, there is room for it to collapse, and I have included a gimmick that makes comebacks easy. This creates an incentive for 'quality over quantity'—not fixing your subsidiaries, but replacing them with companies that have higher earning power.

2. The 'true strength' of a holding company is the average of its subsidiaries

The technical and public relations capabilities of a holding company are the average of the subsidiaries it has collected. In other words, 'what kind of companies you have collected' becomes your own ability. If you buy up companies without carefully examining them just because they are cheap, the group's true strength will also be diluted.

3. Synergy vs. Concentration Discount

We have incorporated the logic of "selection and concentration", where gathering companies in the same industry or country provides a bonus to consolidated earnings, while spreading them too thin results in a negative impact. However, please note that "selection and concentration" increases the risk of antitrust corrective orders.

4. Using Stock as "Currency"

Once a group becomes massive, you can launch large-scale M&As by issuing new shares even with zero cash. This is one of the most dream-like mechanics in actual capitalism. However, issuing new shares causes stock dilution, which (in this game) reduces your capacity for capital increases, ultimately leading to a slowdown in future growth speed. And, as a solution to stock dilution, "share buybacks" are available.

5. Four Formidable Rival Funds

Furthermore, four rival funds will compete with the player. Each rival fund has its own behavioral characteristics: "Aggressive Roll-up," "Bargain Hunter," "Industry Specialist," and "Dark Capital."

They collect companies according to their respective behavioral characteristics (sometimes even going after the player's own listed subsidiaries!), and in the endgame, they compete to snatch each other's listed subsidiaries through hostile takeovers.

If you cannot keep up with the growth of your rivals, there is a possibility that the player's fund will be swallowed up (= game over). "If you don't attack, you lose." The golden rule of capitalism—survival of the fittest—is right here.

Appeal — You Can Choose to be a "Good Manager" or an "Evil Empire"

In this game, we have not provided a single "correct answer."

• Orthodox: Become a massive conglomerate that connects companies, nurtures them, and puts down roots.

• Master Seller: Become a legendary investment fund that buys, nurtures, and sells at the highest price.

• Craftsman Union / Individual Wealth: A craftsman union connected by solid trust that never sells a company once it's under its umbrella, or "individual wealth" that cashes out everything at the perfect timing...

The Option of the Dark Path

And then—the Dark Path. If you dabble in backroom deals, you will receive off-the-books cash every week at the cost of market trust (reputation).

Furthermore, you can use "Information Manipulation" to increase political instability in your base country and suppress the probability of being exposed by authorities (antitrust corrective orders). Your name will be etched in history alongside immense wealth as a secretly feared "Economic Mafia" or "Merchant of Death."

Realistic Capital Circulation and Replayability

Also, even during periods of sluggish stock prices, you can use leverage through borrowing to buy back your own shares to resolve stock dilution, or use leverage through borrowing to buy promising companies. "Increase capital and sell when stock prices are high, and buy back when they are low"—this capital circulation is exactly where you can show your skills.

When the game ends, your final stock price, market capitalization, and earnings power are displayed, and personal historical rankings, global shared rankings, and an "encyclopedia" of the endings you have reached remain. Which ending will you aim for next? That is where the real fun begins.

Development Secret Story — Why did a tax accountant do this?

The starting point was to deliver a 'tangible feel for the economy'

　My main profession is a tax accountant. Every day, I face company numbers and business valuations. I thought, wouldn't it be great to have something where you can experience the "tangible feel" of these words that fly around in economic news—market capitalization, leverage, M&A, regulations—while playing? That was the starting point.

　I imposed a technical constraint on this game: cramming everything into a single HTML file. Thanks to that, this game requires no server or registration; it runs as soon as you open the link.

　The stock price charts, rival funds, and 10 types of endings all run within that single file (only the world ranking uses Cloudflare's serverless infrastructure).

　And my greatest partner was pair programming with AI coding (Claude Code). From discussing the design to implementation and verifying the "balance hell" mentioned later, I worked through it by bouncing ideas off the AI.

　The fact that an individual can create something like this on the side of their main job is undoubtedly thanks to the changes in generative AI over the past few years.

Challenges faced — Balance hell and pitch-black charts

　It didn't end with just the good stuff.

1. The bug where the chart turns pitch black

　When I left the rendering of the stock price chart to the browser's animation function, I was troubled by a phenomenon where the rendering would freeze when the tab was moved to the background, leaving the chart as a black screen.

　I identified the cause and almost completely cured it with a triple defense of "drawing every frame / drawing at fixed intervals / drawing the moment it is recreated" (this bug still happens rarely, so please forgive me...).

2. Balance hell

　This is where I spent the most time. To create that tense, nerve-wracking feeling with "numbers"—"If you don't attack, you lose, but if you attack poorly, you also lose"—I ran a "headless simulation" where I had the AI play dozens of times to measure win rates and absorption rates.

　If you play passively, you get swallowed 100%, and if you attack skillfully, you remain in the race for the top... I chased that golden ratio by repeatedly adjusting coefficients for mechanisms like antitrust laws, capital increase limits, and concentration discounts.

　The dark path is also adjusted to hit the sweet spot of "not too strong, not too weak (cash increases, but it's offset by valuation and investigation risks)."

3. The "incredibly hard to see" problem on smartphones

　Since it's a game with a lot of information, the smartphone gameplay screen was, at first, shockingly unpresentable. I fundamentally rebuilt the mobile interface by separating the information bar from the operation rows and rearranging the lists.

4. Japanese/English support

　I also added multilingual support that automatically displays Japanese if the accessing country is Japan, and English otherwise (manual switching is also possible via the button on the top right). I have translated the entire text into English, not just the UI, but also the news, decision-making, and ending text (since it's AI-driven, there may be some unnatural translations, but please forgive me for that).

Who I want to play this

• For those who want to get a "feel" for management, investment, and capitalism while playing

• For those who enjoy management simulations like Momotaro Dentetsu, A-Train, Capitalism, or SimCity

• For those who want to play quickly in their spare time without registration (but with deep gameplay)

• Business professionals, job seekers, and students interested in economics

• And—those who want to roleplay as a "bad manager" (dark routes are welcome)

Finally

　No registration required, completely free. You can start with just one link, whether on smartphone or PC.

▼Play Capital Empire

　When to buy, when to sell out. Your choices will determine the fate of your empire.

　Please feel free to share your impressions or requests for "features you'd like to see" via the in-game inquiry form. I look forward to hearing from you.

　Please note that all company names, group names, characters, country names, etc., appearing in this game are fictional and have no relation to any real corporations, organizations, or individuals.