How I Keep My Side Project Manageable And Profitable

Hello! What's your background, and what are you working on?

Hi! I’m Holger, a designer-turned-developer from Copenhagen, Denmark. In the last couple of years, I’ve been working on Online Solitaire, a website where you can play classic solitaire card games.

Solitaire has actually been a side hustle of mine for quite some time now. The app started its life years back as a native Mac app, which sold through the Mac App Store, where it earned around $800 a month.

After creating the app, I ended up going to New York with a friend of mine to start a startup called Slang, a marketplace for sneakers and streetwear. This had the effect of leaving my solitaire app on a perpetual backburner. After a couple of years of no maintenance, the app got so buggy that it was eventually booted off the Mac App Store.

As with so many other startups, Slang eventually got beaten by its competitors. After three years of hard work, I was kind of burned out and decided to take some months off to gather my thoughts and maybe do a small project. Once again my eyes turned on solitaire and I ended up building Online Solitaire from the ground up.

At the moment Online Solitaire earns around $1500 a month and I’m hoping it’ll earn more in the future.


What motivated you to get started with Online Solitaire?

I’d like to say a burning passion for playing solitaire, but the truth is that I wanted to see if I could create something earning passive income while working on a small scale project that I liked.

Building something that would make money while I was sleeping was something I was initially inspired to do by reading Patrick McKenzies’s yearly reports on his Bingo Card Creator, a side hustle of his that eventually turned into a real business. Seeing how he could make a simple (and frankly not very innovative) product and make a passive income from it was something that left an impression on me.

I decided to do something similar, in the sense that I didn’t want to “invent” something new since that’s super hard. I wanted to make a better version of an existing product. Which led me to the following criteria for which idea to pick.

  1. I wanted the main source of growth to come from search. The reason being that I absolutely hate doing marketing, outreach and I’m frankly not very good at it either.
  2. I wanted to have the idea to already be validated. In other words, I wanted to find apps/sites out there that people were already using, but where I could see room for improvement.
  3. I wanted that improvement to partly be about the design and user experience since that’s one of my strengths.
  4. I wanted the initial product to only take a few weeks from start to launch, so I could validate if it was worth building on.

I already had a bit of experience building Mac apps, having built a simple calculator, so I knew looking into apps on the Mac App Store would be a good start. I ended up writing a script that would scrape games from App Annie, an app store analytics platform, and rank apps on the basis of average rating, popularity, and revenue. Basically what I was looking for were popular apps with relatively good revenue and bad ratings.

Scrape of Online Solitare's ratings data

As you can see from the chart I ended up with quite a few suggestions. I made an estimate of how much the different apps earned and how hard they would be to make. On the basis of that, I decided to go with solitaire, since it seemed like a good combination of all the parameters and there were multiple solitaire apps such as Spider and Freecell, so there was a possibility of branching out later.

What went into building the initial product?

The initial Mac App Store version was made in three to four weeks of full time work, and I spent about the same time on the web version. Both initial versions were made at a time where I didn’t have a full time job, so I could devote the time to do it.

After the initial versions were made, improvements and updates have been made along the way. It’s never been my intention to turn Online Solitaire into a business, so it’s been important for me to keep it running as a fun little side project. That means I won’t necessarily respond to all emails (though I’ll read them) or implement all suggestions (though I’ll take them into consideration).

What's your tech stack?

Online Solitaire is a React app that uses Firebase as its database. I used Firebase a lot during my time in New York, and I love how simple they make it deal with users and databases. I haven’t found a good use-case for using Firebase’s real time capabilities yet, but I think it’s such a nice feature, so if you have any ideas, let me know!

For animations, I use GSAP. It’s hands-down the best and smoothest JS animation library I’ve tried. Solitaire might not seem like the most animation-intensive game you can come up with, but believe me that it has enough animations (and animation sequences) that doing something in pure JS or CSS animations isn't an option.

I’m using ToDesktop to make a downloadable version of the game. It lets you make a Mac, Windows, and Linux binary of your site. It’s still a relatively new service and is missing some features, but from talking with the guys behind it, they’ve been really helpful and they seem to be moving fast.

How have you attracted users and grown Online Solitaire?

It’s all about getting users to find you through search. In other words, it’s all about SEO. No one is going to write long articles about your new innovative solitaire game. Everyone knows what solitaire is and not much new can be said about it. It’s one of those things people search for when they want to play a game and otherwise it doesn’t enter their mind.

In the case of Online Solitaire working on optimizing pages for SEO with the help of Moz’s on-page optimization and slowly building backlinks, has been key to ranking on Google. I’m not ranking super well, but I get around 1,000 clicks a day from Google.

At one point I was getting around 2,000 clicks a day, but because of a foul-up on my side, I’m down to 1,000 again. The site used to be hosted one another domain, but when I got the chance to buy I jumped on it. The foul-up consists of me forgetting to renew the old domain, so all the backlinks that were redirecting to the new domain got dropped.

graph of Online Solitare's search results

What's your business model, and how have you grown your revenue?

Ad revenue. There’s no way around it. I’ve been thinking about making a subscription model for those people who spend hours playing solitaire (believe me, they exist), but solitaire is something that the vast majority of folks are not willing to pay for.

When you decide on an ad network, give the revenue a couple of months to “settle in”.


I’m not a big fan of ads myself (big surprise), but I have to earn some money on it to justify the time I end up spending. I’ve implemented a “hide ad” feature, which people can click to hide ads for a day, and if people use ad-blocker then I don’t annoy them with popups telling them to turn it off.

The biggest impact I’ve had on revenue is the choice of ad provider. The ad network landscape is big and can be very confusing, so it’s good to do some research about the different providers. I searched Reddit a lot to read about peoples experiences. When you decide on a network, give the revenue a couple of months to “settle in”.

I first implemented Google Adsense, which netted me around $10/day, then I tried out Monumetric, which earned me around $25/day and now I’m with Freestar, which earns me around $50/day. If revenue strategy is based on ads, I can definitely recommend trying out different networks, since not all networks work equally well for all sites.

What are your goals for the future?

First and foremost, I want to keep this a side hustle. I don’t want Online Solitaire to become a source of income that I’ll have to rely on. There’s a good amount of competition and if Online Solitaire gets ousted, I don’t want it to be a catastrophe. In other words, I don’t want the site to keep me awake at night.

As for the summer holidays, I’d like to spend some of it on expanding the options of solitaire games. Right now the site has Klondike, Spider, and Freecell, which are the three most popular solitaire games, but there is an abundance of different solitaire games out there.

I also want to become better at doing SEO-related stuff. It’s one of those tasks that I really don’t enjoy, but nevertheless it’s what gets your site ranking on Google and therefore users to your site.

What are the biggest challenges you've faced and obstacles you've overcome?

One thing I’ve had a hard time with is talking about the app with other people. Throughout the last couple of years my solitaire app has at times been the most interesting project I’ve been working on, but it’s kind of hard to take seriously since it’s just a silly old game. So whenever people asked me if I was doing anything interesting at the moment, I’d be a bit hesitant to mention it.

Talking with people and getting their feedback is the best way to improve your product, even if your product is just a silly old game.

If you had to start over, what would you do differently?

If I were to start over, I’d focus a good deal more on the things I don’t like to do.

I enjoy design and development (to some extend at least), but when it comes to marketing and SEO I prefer to let someone else take over. That’s not an option if you’re a one-man team though.

Have you found anything particularly helpful or advantageous?

Both the initial version for the Mac App Store and the web was born out of sub-optimal circumstances. I made the Mac App Store version while I was between jobs and I made the web version while I was taking a breather from co-founding a startup. So making the best of a “bad” situation is definitely something that’s been helpful to me.

If I were to start over, I’d focus a good deal more on the things I don’t like to do.


I think having a background in design has been advantageous for me as well. There’s a lot of good solitaire apps out there, but most of them seem to have been made by programmers without much design input.

What's your advice for indie hackers who are just starting out?

Ship, ship, ship. First and foremost, get something out there as soon as you possibly can. You’ve heard it before, I know, but it's just the number one piece of advice I can give. You need that initial validation from the users so you know you’re on the right path. If you’re not convinced, then take a look at my Jigsaw Puzzle site. I’ve spent as much time on that as the initial version of Solitaire and get a negligible amount of users each month.

Know your strengths and your weaknesses. I spend the better half of last summer working on a habit tracker called Habitual, which never really got off the ground. I’m sure there are lots of improvements that I could make on it, but I’ll never know because I’m such a bad marketer, which for an iOS app can leave you stranded in regards to getting users. So if you’re lacking some skills that are crucial to getting your project off ground, you’d better learn them or team up with someone who possesses them.

I still use Habitual myself and maintain it, so if you’re a marketeer of some sort and see potential in it, let me know.

Where can we go to learn more?

If you like to play solitaire you should definitely try out a game at

If you have any suggestions or feedback for the site, please let me know at [email protected].

If you want to get into contact with me personally you can find me on, Linked In, or shoot me an email at [email protected].

Feel free to ask any questions below and I’ll answer them to the best of my capability.

Holger Sindbaek , Founder of Online Solitaire

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  1. 3

    That App Annie scraping script was genius and an excellent way of surfacing new app ideas. Is it open source or available for purchase? Thanks for the great interview regardless.

    1. 2

      It's an old script, so I'm not sure it's working anymore. Write me an email and I'll send the script to you.

      1. 1

        Hi there!
        I was wondering if you could send me that script too.
        I was amazed by your project, and how you get the idea of what to build. :)

        1. 1

          Sure thing. What's your email?

          1. 1

            huszijozs at

            Thanks in advance! :)

      2. 1

        Email sent. Thank you..

  2. 2

    Great interview! I think your point about "deciding to do something similar, in the sense that I didn’t want to “invent” something new since that’s super hard. I wanted to make a better version of an existing product" is extremely important.

    New inventions are great, but there are a myriad of products that are great in their original concept, but remain poorly executed.

  3. 2

    This is absolutely great and inspiring story. Could you share some of the back-linking strategies you’ve used? Thanks for the reply!

    1. 1

      The whole SEO-world is still kind of new to me, so I'm still working on that. You've probably already guessed that writing this interview is partly a backlinking strategy. I find it hard to sites who would like to link to a solitaire site. If you have any ideas, please let me know at :-).

      1. 1

        Well, I'm complete novice, so for me what you're doing seems to have solid results if SEO is your main strategy . I'll definitely checkout Moz software, so that was a great tip.

        Also, just wanted to complement great choice of the font. I think it adds just the right amount of playfulness to the app. And in general, it's just very well done. Great job!

        Can you recommend any resources besides Moz?

        1. 2

          Thanks a lot :-).

          For learning SEO, I'd definitely recommend Backlinko: They make great longform blogposts and keep them updated. Basically all I know about SEO comes from there.

          1. 1

            backlinko looks fantastic. thanks a lot!

            1. 1

              It most certainly is. He really knows what he's talking about. His articles are REALLY long, but worth the read if you want to get properly into SEO.

  4. 2

    This is an interesting read for me, I built a suite of card game sites over the past few years and sold them last year for the mid six figure range. At peak they were making between 10 and 15k a month, completely passive.

    I can't talk more about the exact sites here because of NDA but if you want any advice on increasing your revenue or bettering your SEO, I'm glad to help.

    Best of luck regardless!

    Edit: I also thought about doing a paid version to get rid of ads at just $3-4 per month and this was for access to 6 different cards games - got maybe 2 or 3 people interested out of the 10's of thousands of uniques when I put out a month long "invite" as a test. So IMO probably not worth it.

    1. 2

      Damn Willie... seems like you took my game to the next level :-). I couldn't find your email on your profile, but I'd love to hear more about your journey, what worked for you and what didn't. Personally I'm struggling a lot with SEO at the moment. Feel free to write to me at or [email protected]. Hope to hear from you :-).

  5. 1

    I like the site, I've used it for fun a couple times since I first read this to kill a few minutes with solitaire.

    You asked what you could use firebase's real time database for and IMO, what firebase is best used for is progressive web apps (PWAs) which you should totally look into making online-solitaire into. Then, users could just install it on their phone and it acts similar to a native app.

    Firebase works seamlessly with the browser's "indexed db" to make transitioning from offline to online super smooth in my experience.

    When I was first learning about PWAs and firebase, I ran into a youtube account called "The Net Ninja" and I'd 100% recommend his PWA intro series if you're into video introductions over reading docs. Specifically he uses firestore but that's just the successor to the firebase real-time db.

  6. 1

    Great read! Have totally no experience with web or mac os apps, so I'll leave it at that :). Inspiring.

    1. 1

      Thanks :-).

  7. 1

    What's your general experience with games on the macOS App Store? I have an iOS game (see and I'm curious regarding releasing a version for mac as well, but I'm not sure it will be worth the effort (the effort probably not being huge since it's built with React Native which can produce mac apps as well).

    1. 2

      The only thing I can say about that is that the macOS crowd is much smaller, but the competition is much smaller as well. My iOS app (Habitual) I talked about drowned in the iOS store, because the store is so big. The Mac app store is much smaller, so there's a bigger chance people will see your app.

      1. 1

        Yea, I figured as much, but do you have any numbers regarding Habitual on iOS vs Mac App Store that you could share? Have you been surprised by anything in that regard? Have you been more successful (revenue-wise) on the mac app store?

        1. 1

          Habitual doesn’t exist for Mac, so I only have the comparison of my old Solitaire Mac app compared to Habitual. The only real knowledge I have is the one above.

    2. 1

      Might be less effort than you think soon. All compatible iOS apps will automatically be made available on macOS app store when the new ARM powered macs are released. I have a few React Native apps and when I log into app store connect it says they are all compatible.

  8. 1

    Great interview and great side project. I checked out your website but I don’t see any ads or how to show/hide them.

    Also when you tried AdSense for games, did you have any issues with this requirement:

    “ Have a high volume of games content, i.e., greater than 70% games content with over 1 million games impressions monthly.”

    Or did that requirement not apply to your site?

    Thanks for your insight and for sharing your story.

    1. 1

      The ads should show after 5 games or so on the right side.

      To be honest, I never really read the requirements. I just applied and hoped for the best.