Compound interest. Playable.
I still vividly recall the feeling of seeing the value of my modest investment portfolio unexpectedly taking off like a rocket: mind-blowing, eye-opening, and quite humbling. Suddenly the effort of almost four years of consistent investing, the first two not even producing green numbers at all, completely made sense.
The reason? Compound interest: the snowballing effect of capital gains on your money making their own gains, and those gains making their own gains as well. It's often referred to as the 'eighth wonder of the world', and the silent force behind the fortunes of some of the wealthiest people on the planet. They are reaping its benefits after many years of consistent investing or building a business.
The beautiful thing about compound interest is that literally anyone has a chance at harnessing its effects, including you. Maybe not at billionaire-level scales, but that shouldn't matter. Even modest sums can already work for you in a very impactful and freeing way.
Still, there is only a relatively small number of Compound Kids in the world. They are the people who have been fortunate enough to experience the phenomenal power of compound interest in front of their own eyes. And that's a shame, because I believe this experience can genuinely be eye-opening for anyone.
That's why I've created Compound Kid, an arcade game that lets you experience the genuine "holy shit" feeling of compound interest turning small sums into extraordinary wealth. Playing the game will let the concept click for you in a way that no textbook or finfluencer explanation will ever achieve.
In real life, this experience would require years of patiently investing or building a business. Skilled Compound Kid players will generally be able to experience those same astounding effects in less than three (!) minutes.
The game lets you play a character, loosely based on my younger self, running across a trend line with the goal of collecting as many coins as possible. A single tap on the screen makes the character jump over the obstacles in his way.
For each collected coin the value of your already collected coins grows by 10 percent, just like the historical growth rate of the US stock market. A run ends when your character runs, jumps, or falls into one of the obstacles, after which you can try again.
The more coins you collect, the more your score progression will show signs of explosive exponential growth, and it's at this point that the power of compound interest will truly show itself.
Don't, however, be fooled: Compound Kid is a simple game, but not necessarily an easy one. The game requires genuine skill in timing your jumps and maintaining your focus long enough for the effects to become visible. The margins of error are deliberately small, so a mistake is easily made.
After having played the game for a while, and hopefully having experienced the mind-boggling effects of compound interest yourself, I hope that well-known sayings like "the rich keep getting richer", "start investing early", or "the first $100k is a b*tch" will make more sense to you.
And hopefully, you'll also find ways of bringing the lessons from the game to your own life. Maybe the game can inspire you to start your own investing journey, take a chance on that business idea, or help you push through tough times knowing that many of life's rewards often tend to follow after long periods of seemingly little progress.
The game is a passion project, so it's completely free to play. I also hope that it gives you more than it can ever extract in return. Yes, there will be a couple of ads here and there to generate a little extra income for my family, and I hope that's alright. All ads are deliberately placed to interfere as little as possible with the gameplay and your experience.
So if you're completely new to the topic, or considering starting your own investing or business journey, I hope Compound Kid can show you what might be ahead. If you're already well underway, I hope this game can be a great reminder of what you're doing it for. And if you're already a Compound Kid who's seen compound interest working for them in real life, I hope this game can give you that same thrill again.
Good luck playing, and enjoy!
- Stefan, a fellow Compound Kid
P.S. If you're really struggling, it's good to know that there is actually a winning strategy for the game. This secret will be handed to you after 30 games played, so that you have enough time to figure it out for yourself first.
Last updated: September 26, 2026
Entertainment, not financial advice. Compound Kid is a game. While it is built around a real financial concept, compound interest, and may leave you with genuine intuition about how money grows over time, nothing in the App constitutes financial, investment, tax, or legal advice.
The numbers, outcomes, and "returns" you see in-game are simplified for gameplay and entertainment purposes, do not reflect real-world investment performance, and should never be used as the basis for an actual financial decision. Always consult a qualified, licensed professional before making financial decisions.
1. Acceptance of These Terms
By downloading, installing, or playing Compound Kid (the "App"), you agree to these Terms of Use. If you do not agree with them, please do not use the App.
2. The App Is Provided "As Is"
The App is provided free of charge, "as is" and "as available," without warranties of any kind, whether express or implied, including any warranty that the App will be uninterrupted, error-free, or fit for a particular purpose. You use the App at your own discretion and risk.
3. Not Financial Advice
As stated above, nothing displayed, calculated, or implied within the App, including any in-game currency, coin values, score charts, or explanatory text, is intended as, or should be relied upon as, financial, investment, tax, legal, or other professional advice. Any resemblance between the App's mechanics and real financial markets or products is for illustrative and entertainment purposes only.
4. Acceptable Use
You agree not to:
- Reverse-engineer, decompile, or disassemble the App, except where applicable law expressly permits it
- Use any automated system, such as bots, scripts, or cheats, to interact with the App in a way not intended by normal human gameplay
- Use the App for any unlawful purpose, or in a way that could damage, disable, or impair its operation
5. Intellectual Property
All artwork, characters, code, copy, music, and other original content in the App belong to the developer, except for third-party components, such as the Phaser game framework and Google Mobile Ads SDK, which remain the property of their respective owners and are used under their own applicable licenses.
6. Advertising and Third-Party Services
The App displays advertising served through Google AdMob. Your interaction with ads is governed by Google's own terms, in addition to this document. See the Privacy Policy below for details on what advertising-related data is collected and by whom.
7. Limitation of Liability
To the fullest extent permitted by applicable law, the developer shall not be liable for any indirect, incidental, special, consequential, or punitive damages, or any loss of profits or data, arising out of or related to your use of, or inability to use, the App, including any financial decisions made after playing it.
8. Changes to the App or These Terms
The App and these Terms may be updated from time to time. The "Last updated" date at the top of this section will always reflect the most recent revision. Continued use of the App after changes are posted constitutes acceptance of the updated Terms.
9. Governing Law
These Terms are governed by the laws of the developer's country of residence, without regard to its conflict-of-law principles, except where applicable local consumer-protection law grants you rights that cannot be waived by agreement.
10. Contact
Questions about these Terms can be sent to:
Last updated: September 26, 2026
This Privacy Policy explains what information is collected when you play Compound Kid (the "App"), how it is used, and what choices you have. It is written to be read by a human, so if anything is unclear, the contact details at the bottom are there for exactly that.
1. Who This Policy Covers
This policy applies to anyone who downloads or plays the App on Android or iOS. The App is a passion project developed and published by an independent, individual developer, not a company or organization.
2. Information the App Itself Does Not Collect
The App's own code does not collect, transmit, or store any personal information on a server. Specifically:
- Your score, coin count, and high-score history are stored only on your device, in local app storage, never uploaded anywhere.
- The App does not require an account, login, or email address to play.
- The App does not access your contacts, photos, location, microphone, or camera.
If you uninstall the App, this locally-stored data is deleted along with it.
3. Information Collected by Third-Party Advertising
The App is free to play and is supported by advertising served through Google AdMob. To deliver and measure ads, Google and its advertising partners may automatically collect certain technical information, which can include:
- Device identifiers, such as your device's advertising ID
- IP address and approximate, non-precise location derived from it
- App usage and interaction data related to ads, such as ads shown, clicked, or dismissed
- Device type, operating system, and general technical information
This data collection is carried out by Google and its advertising partners as independent data controllers, under their own privacy policies, not by the App developer. You can review how Google handles this data here:
- Google Privacy Policy
- Google's Partner Consent Requirements (EU)
- How Google uses information from sites/apps that use AdMob
4. Your Consent Choices (EEA, UK, and Switzerland)
If you are located in the European Economic Area, the United Kingdom, or Switzerland, the App presents a consent dialog the first time it is opened, in accordance with Google's EU User Consent Policy and applicable law, including the GDPR and UK GDPR. Through this dialog you can:
- Consent to personalized advertising, or
- Decline personalized advertising and receive non-personalized ads instead, or
- View the full list of advertising partners and their individual purposes before deciding
You can change your choice at any time by clearing the App's storage or data in your device settings, which will cause the consent dialog to appear again the next time you open the App.
5. Your Rights Under GDPR
If you are located in the EEA or UK, you have the right to:
- Access: request confirmation of what personal data is processed about you
- Rectification: request correction of inaccurate data
- Erasure: request deletion of your data, also known as the right to be forgotten
- Restriction: request that processing of your data be limited
- Objection: object to processing, including for advertising purposes
- Data portability: request your data in a portable format
- Withdraw consent: at any time, without affecting the lawfulness of processing before withdrawal
- Lodge a complaint: with your local data protection supervisory authority
Because the App itself does not collect or store personal data on a server, most of these rights are exercised directly with Google as the party actually processing advertising data. Google's own data subject request tools are linked in Section 3 above. For anything related to the App itself, you can also contact the developer using the details in Section 9.
6. Your Rights Under US State Privacy Laws
If you are a resident of California, Virginia, Colorado, Connecticut, Utah, or another US state with a comprehensive privacy law, you may have the right to:
- Know what personal information is collected about you and how it is used
- Delete personal information collected about you
- Opt out of the sale or sharing of personal information, including for cross-context behavioral or targeted advertising
- Non-discrimination: you will not be denied service or charged differently for exercising these rights
- Correct inaccurate personal information, where applicable under state law
As noted above, advertising-related data collection is performed by Google as an independent controller. Google provides its own opt-out mechanisms for US state privacy rights, accessible via the links in Section 3.
7. Children's Privacy
The App is not directed at children under 13, and the developer does not knowingly collect personal information from children under 13. If the App is configured for a family or "designed for families" category on the app store, ad serving is restricted to non-personalized, contextual ads only, in compliance with Google's Families Policy and applicable children's privacy laws, including COPPA in the United States. If you believe a child has provided personal information through the App, please contact the developer using the details in Section 9 so it can be addressed.
8. Data Retention and International Transfers
Locally-stored gameplay data, such as scores and high scores, remains on your device only, for as long as the App is installed, and is not retained by the developer in any other location. Advertising-related data collected by Google and its partners is retained and may be transferred internationally in accordance with their own policies, referenced in Section 3.
9. Contact
Questions about this policy, or requests relating to your privacy rights, can be sent to:
10. Changes to This Policy
This policy may be updated from time to time, for example to reflect changes in advertising partners or applicable law. The "Last updated" date at the top of this section will always reflect the most recent revision. Continued use of the App after changes are posted constitutes acceptance of the updated policy.
Did compound interest click for you after having played the game? Compound Kid is made for entertainment and illustration purposes, and we all know that real-life investing and building a business are much messier. This page is for the moment after you've played the game, when you wonder what it all means in real life.
As stated in the Terms of Use, nothing in the app or on this website is financial advice. Nevertheless, I see no problem in sharing the experiences, materials and communities that have helped me see compound interest at work in real life.
You won't find any links here. The game isn't affiliated with anything mentioned in this section, and I don't want to give the impression that I earn something from doing so.
Where the game matches real life
Compound Kid resonates with the road I went through myself, at least in some respects. The biggest similarity happened when the game reached a playable state. To my own surprise, my amazement at seeing compound interest at work in the game was actually very comparable with my real-life reaction when the value of my own modest investment portfolio started accelerating.
In both real-life and the game, the process towards reaching the point of visible compounding felt extremely slow. It took me around four years of frugal living and aggressive investing before clear signs of the snowball effect became visible, which happened around reaching the six-figure mark. From there the numbers have simply kept snowballing since, with time being the main ingredient doing the heavy lifting.
The pace with which your money keeps compounding is generally explained in personal finance through the so-called 'Rule of 72'. If you divide 72 by your annual growth rate, you'll get roughly the number of years it takes for your money to double. In the game you will find that the growth rate of 10% causes your score to double roughly every 7 coins you collect, showing those same mathematics in practice.
Where the game differs from real life
The game shows compounding through steady returns that are not influenced by external factors. In real life, however, markets of course fluctuate and returns will vary from year to year. You will also have to deal with inflation, fees and taxes. As a result, your true growth rate will often be lower than initially projected.
Long stretches of losses are unavoidably part of the journey as well. When I started my own investing journey, I unknowingly did so at the beginning of a bear market. It took almost two years, and a lot of doubt underway, before my portfolio permanently turned green. I've found that staying calm and true to your plan while portfolio values fluctuate is by far the hardest part of investing. The game makes explicit that staying in the game long enough to get lucky is critical for compounding to succeed, but can't simulate the real life emotions that accompany the journey.
The time frame to achieve success is, of course, also completely different compared to real life. A skilled Compound Kid player will generally experience meaningful snowballing effects in less than three minutes, usually between a score of 100k and 1 million. In real life, those minutes are years, if not decades.
Books
Money is an interesting topic for many of us, and the number of finance books and authors is high. Many of the ones I've read are fairly interchangeable and tell more or less the same story, but four stood out. They're the ones that have fundamentally influenced my view on money and helped me with getting where I currently am.
The first is The Psychology of Money by Morgan Housel. It captures better than any other book I know the effects money can have on people, while simultaneously showing how familiar finance principles play out in reality.
The second is The Richest Man in Babylon by George S. Clason. It's a quick read, and a nice allegory that illustrates the power of compounding through different short stories. The book dates from 1926 and remains an entertaining read, which really shows how timeless the topic of compound interest is.
The third is The Millionaire Next Door by Thomas J. Stanley and William D. Danko, which fundamentally changed my idea of what a wealthy person looks like. If you look beyond the extensive tables and charts in the book it paints a detailed picture of the people who benefited most from compounding returns in their lives, and the habits that got them there. Spoiler: they usually can't be identified by their material possessions.
The fourth is The Wealth Ladder by Nick Maggiulli. This book convincingly explains how different levels of net worth affect your money habits and options. What I liked most about the book was it adds a lot of nuance to the often-heard advice to "start investing early". Anyone can invest or build a business, absolutely, but your financial situation might require you to build a strong buffer first before allocating money towards long-term compounding.
Communities
There are entire communities built around harnessing the powers of compound interest. The most well-known is the FIRE (Financial Independence, Retire Early) movement. The philosophy of this movement is to save a large share of your income, invest it, and let the resulting compound growth eventually cover your living costs. Since there are different degrees of independence there are also different FIRE variants, of which Fat FIRE and Coast FIRE are two well-known examples. Although I wouldn't necessarily consider myself a FIRE-adept I've often found exploring the stories within the FIRE community to be very inspiring, since most of them are ultimately about regular people trying to a live life in a way that is meaningful to them.
Other investing communities and public figures center their thinking on compounding, too. The Boglehead community, for example, follows the philosophy of Vanguard founder John Bogle. By investing in well-diversified index funds with low management fees, they aim to maximize compounding potential at manageable risk. Warren Buffett and the late Charlie Munger of Berkshire Hathaway have also discussed the concept of compounding extensively, and you will find that many finfluencers draw inspiration from their quotes and their approaches to investing and building a business.
A Special Shout-Out
My own investment journey started with a Dutch podcast recommended by one of my best friends, called 'Jong Beleggen, de podcast'. It follows a young entrepreneur who made significant money from selling his business and decided to invest part of the proceeds in the stock market. Together with a co-host he documents his investing journey, while being completely transparent about the value of his portfolio and the emotions he went through.
I listened religiously for a year before starting my own investing journey, when I was finally in a position to invest for the long term without problems. Their transparency, experiences and lessons helped me understand the basics and stay the course, even when the numbers turned red. I listen less often now that the show covers more niche topics, but a special shout-out is well deserved.
Where to start
There are ample ways to further dive into the topic of compound interest, investing, entrepeneurship, and personal finance. If you haven't already done so, maybe some of the things that have helped me might do the same for you.
Regardless of which step you take next, know that you're always welcome to return to Compound Kid if you ever want to experience the amazing effects ofcompound interest again!