At User Camp, we’re advocating for indie software in the Microsoft Store. This is the first in a series of interviews with successful Store developers.

Imagine an indie app that dominates its niche, has gobs of delighted users, and costs real money (instead of peppering its users with banner ads or hassling them for IAPs). Now, guess which platform it’s on.

This is a story that’s not uncommon on iOS, where wallet penetration is high and pirating apps is a challenge. But it can happen in the Microsoft Store, too. One developer, Timo Partl, did it in just 11 months by identifying an underserved niche and going on a one-man mission to close the app gap.

Now, Diarium has been nominated by Microsoft for the App Creator of the Year award. (You can support Timo and reward him for creating an outstanding Windows 10 and Windows Phone-exclusive app by voting for Diarium until April 27th.)

We asked Timo how he identified the opportunity for his app, executed on it, and brought it to its current popularity and recognition from Microsoft:

What made you develop Diarium?

I saw my girlfriend putting lots of effort into her daily agenda — around 20 minutes a day, including small stickers, pictures and quotes.

I wasn’t even aware that people still used diaries, but she showed me that they can still can be something truly personal and valuable. After she told me about the costs for a one-year diary, the stickers, and the photos, I was pretty shocked.

As an app developer always searching for new app ideas, I felt like I had found one. I searched the Windows Store for diary apps, but there weren’t any decent ones in my eyes, even though there were plenty in the Google Play Store and Apple App Store. So I felt like I had to fill the app gap on the Windows side, and started coding.