Over the last year and a half, in my spare time, I wrote an app called The Fourth Dimension, for iPad, iPhone, and iPod Touch. The app is a 30 page interactive book that explains the concept of a fourth spatial dimension, and in particular, what a tesseract is.
Before launching, I assumed that my app was far too obscure and geeky to be even remotely successful. I expected that only a few dozen people would find out about it, but to my surprise, it got a nice amount of attention and made $13,945 in its first three months. In the App Store, the app has received an average of five stars from 220 user reviews. It has sold 6769 copies. The Fourth Dimension briefly reached #5 in Education twice for both iPhone and iPad, #221 overall (all categories) for iPhone, and #95 overall for iPad.
When I was 15 years old, back in 1986, I read a Scientific American article about how to write a program to visualize a hypercube, and I implemented my own version in BASIC. The Fourth Dimension is my third iteration of that program. I wrote this version because I wanted to experience what it'd be like to hold an interactive tesseract in my hands on an iPad. While developing the app, I always imagined that I was writing it for the 15-year-old me. I hoped that the app might inspire another generation of kids.
I first started thinking about writing this app about two years ago. Three weeks later, StarCraft 2 was tragically released and I wasted at least half a year honing my Protoss skills before resuming work on the app.
When I started the project, I wasn't sure if I would ever finish it, so I experimentally implemented only a simple interactive tesseract, with 3D and 4D touch-based rotations, over about a month and a half. Satisfied with this, I designed the rest of the app on paper in about a week. I stuck to this design during the development process, without significant revision.
I neglected to do any visual design early on because, as a programmer, it was natural for me to get too caught up in the technical issues. This became a problem later, once I realized that what I had created so far was disappointingly ugly. Midway through development, I stopped and did some visual design work, using computer displays in the movie 2001 as inspiration. For the next app, I plan on doing all of the visual design before writing any code.
I don't have good records, but a rough estimate is that I spent about 400 hours developing the app, much of that while watching TV with my wife when our kids were asleep. Usually I was not distracted by the TV, but I experienced a significant lull in productivity when Downton Abbey aired.
I did most of the work, but two friends helped with 3D modeling and programming and sound effects. I used Jira for issue tracking. On the next project I am going to use Trello because it is fast and lightweight and better suited for a small project.
I wrote the app in Objective-C and used OpenGL ES 2.0 for the graphics and animation. I used Garage Band to create the mysterious dimensionless void background sounds.
Before launching, I did quite a bit of user testing with real live people, both geeks and non-geeks, and modified the app based on that feedback to smooth out the user experience. I had about two dozen people test the app remotely, using TestFlight.
To launch the app, I created a web site and an amateurish YouTube video. I kept the video under 30 seconds so it wouldn't waste the time of potential reviewers. On the last page of the app, I provided buttons encouraging users to tweet and Facebook-share about it. I have a personal web site that gets a small amount of hits via Google searches for topics like the distance from the Earth to the Moon and hypercube, so I added links to the app there.
I put the app in the Education category and priced it at $2.99. Friends told me that I should make the app free, or charge $0.99, but I spent so much time working on it and quibbling over subtle details that I felt that I deserved more for my effort. Mercifully, reviewers on big web sites wrote in their reviews, “It's priced fairly low” and “This app is totally worth the three dollars you're asked to pay for it.”
On launch day, friends and coworkers posted about the app on Twitter and Facebook and this generated a few sales. A few days later, I noticed a little spike and traced this to a number of enthusiastic tweets among indie game developers. Based on this information, I posted to Reddit, targeting this interest group.
The Reddit posts generated a small number of sales, but tweets referencing these posts caught the attention of Digg, which resulted in a cascading series of improbable events that led to coverage by BuzzFeed and The Verge, for a total of $5660 sales (after Apple's 30% take) in the first two weeks.
Later, Cult of Mac reviewed the app, resulting in $2102 in one day.
The Fourth Dimension received many wonderful comments from users in the App Store:
“This is how all things out to be taught. It's a polished, visceral handholding through a complex idea that greatly helped my comprehension of the subject. This app is how Starfleet would teach abstract ideas on the Enterprise. It's that good. Please bloody please create more educational apps in this vein.” — Daniel Philips
“Astounding. That some people care passionately enough about tesseracts to go create a fantastic app for others to understand them is incredible. The app is extremely well designed, wittily written, and executed with love. That alone is worth buying it, besides the fact that I learned what the hell a tesseract was.” — Duncan MacMichael
“Fantastic app. I work at a leading UK university. If only all our material was this well written and presented. Definitely worth buying and then spending a bit of time with over a day or two to get your head around the fourth dimension. Great app!” — JulesFM
“Mind blowing! I cannot believe this! It is literally insane! I'm only 15 and I've never really understood the idea of dimension... starting to get the hang of it. Will take the next few days to figure it out. So what is the fifth dimension?!” — Robert Lane
That last comment, in particular, made my day. Inspiring a 15-year-old kid was my goal from day one. Mission accomplished.
I pitched the app directly to news writers at a few larger web sites, and got requests for promo codes from Discovery News and The New York Times, but nothing ever came of these inquiries. I was excited to get any response from them at all.
I experimentally paid for ads on BuySellAds, and this resulted in nearly zero sales. I saw other highly ranked apps in the Education category advertised this way, like Max & Ruby: Max's Mole Mash, and naively assumed that big companies like Nickelodeon were doing this for a good reason, and that I could also benefit. Oops.
I used a free Google AdWords credit and saw almost no sales activity from this.
I tried some in-app advertising experiments with a friend who wrote an awesome solitaire app that has a huge number of users, but this resulted in almost no sales because the demographic of my friend's app appears to be retired German women who are not interested in higher dimensional mathematics.
Since the reviews stopped, I have been selling about 5 to 10 copies per day. I think this comes from a mixture of referrals via my personal web site and people coming across the app from within the App Store via search keywords.
People will buy apps about obscure math topics. Mind == blown.
Make an app that is sufficiently unique and interesting and web sites will review it. When designing the next app, I keep asking myself, what is the big story? Why would anybody write about this?
I was lucky that The Fourth Dimension magically found its way into the hands of a small number of geeky reviewers who were part of the app's target demographic. My efforts to reproduce this process on demand were relatively unsuccessful, even when I targeted writers directly.
Paid ads appear to be worthless.
I have an old personal web page about how to make a thing in a jar and it gets about a million hits per year via StumbleUpon. I was hoping that this would act as a great advertising channel, but it looks like most StumbleUpon users glance at the page and then immediately skip to the next site, resulting in an extremely low click through rate.
Despite reaching #5 in its category twice, my app was never featured in the App Store under New & Noteworthy. However, I've seen summaries of other apps that were featured, and made a similar amount of money. So, while getting featured is great, it's possible to be equally successful without getting featured, if you can get reviews on big web sites.
I have read that free apps get a lot more downloads, and that in-app purchases do well. For my next app, which will also take the form of an interactive book, I plan to make it free to try the first 15% of the app, and make the remaining 85% of the content available as an in-app purchase. Hopefully, the free portion of the app will act as an effective advertising channel.
What keeps apps like Star Walk and Solar Walk permanently up in the top 25 of the Education category? Several times, my app shot up into the top 25 or top 10, driven by good reviews on web sites, but this was always temporary, and the app's mere presence in the charts wasn't enough to keep it highly ranked for more than a day or two. Does the company behind Star Walk and Solar Walk advertise somewhere or do anything else to keep its rank up via pressure from outside the App Store? Star Walk and Solar Walk are great apps. Are they simply so wonderful that enough users buy them every day to keep them up in the rankings, even years after release, merely because they are visible in the App Store?
How is anybody making a profit off the ads on app review web sites provided by BuySellAds? I am baffled that my rate of return was so low. Why do these sites feature ads at all? Did I do this wrong?
The BuzzFeed review was read by 10,000 people, resulting in about 500 sales. Scaling this up, if I could pay $25,000 for a positive review that was guaranteed to be seen by 1,000,000 people, resulting in 50,000 sales, I would jump at this chance. The reviews have demonstrated to me that if people find out about The Fourth Dimension, they'll buy it. Where do I plug in the money to make this happen?
Is there anything else can I do to drive sales?
Please email me at email@example.com if you have any illuminating answers or comments.