More dynamic than Sudoku. Ukrainian indie developer releases math puzzle RiddleSum for iOS and brings it to the Korean market
Indie developer Dmitry Romanov has released RiddleSum, a math puzzle game that combines logic and working with numbers.
Indie developer Dmitry Romanov has released RiddleSum, a math puzzle game that combines logic and working with numbers.
Romanov, as he told dev.ua, has many years of experience in developing mobile applications: he has participated in the creation of both large-scale commercial projects and his own products, and in the last few years he has focused specifically on his own mobile applications, in which he combines accumulated user experience, well-thought-out game mechanics, and modern development technologies from Apple.
RiddleSum is mostly a solo project: Romanov is responsible for the code, design, and product vision, and an acquaintance helps him with testing and basic marketing. The biggest investment in the product is the developer’s time: work has been going on in several waves since 2023, from the first prototype to regular product updates.
Where did the idea come from?
According to Romanov, the game’s mechanics are not unique, but they are not too common either — he once came across a very basic web version of such a puzzle, without a thoughtful design or product presentation. He was struck by the contrast: the rules are simple, but during the game there is a real pleasure in finding patterns and the moment when the solution is formed in the head.
The developer compares the gameplay to Sudoku, but notes that RiddleSum is more dynamic—levels tend to be completed faster, so the game works well as a short intellectual break during the day. After returning to the web version a few times for another level, Romanov decided he wanted to have that experience in a convenient mobile format.
At first it was a small project «for myself», but in the process it became clear: simply porting the mechanics to the phone is not enough. If you are going to invest time, you want to make a full-fledged game — with a progression of difficulty, a clear entry, your own visual style and reasons to come back.
What is the point?
The player’s task in RiddleSum is to arrange the numbers so that the sum in each row and column corresponds to the values indicated on the edges of the playing field. Technically, this is done by crossing out the extra numbers and circling the correct ones — those that add up to the desired value. Each puzzle has only one correct answer, and you need to simultaneously consider the correctness of the sums in both rows and columns.
The game offers fields of various sizes — from small 3×3 to large 9×9 — and gradually becomes more difficult, forcing you to analyze, look for patterns, and train your mental arithmetic skills. At the same time, the application has no time limits, there are hints in case the puzzle is not solved, and the interface itself is minimalistic and clean.
The first important addition to the basic mechanics was the progression of difficulty. The most difficult thing was to set the pace: the game should not suddenly become too difficult, but it should not remain easy for too long, otherwise interest would disappear. At first, Romanov was guided by his own feelings, and then he involved acquaintances for testing — their feedback helped to understand where new players lacked explanations, and so the game had an interactive tutorial — a basic level at which the mechanics are explained through action.
Monetization without intrusive subscription
After the first releases, Romanov also tested paid promotion, which quickly showed how competitive the casual puzzle market is: attracting users is expensive, and the advertising model requires significant traffic. At the same time, there was a clear request from players to be able to play without ads — so in the latest release there was a one-time purchase to disable them. According to the developer, he deliberately did not want to build an intrusive subscription for such a game.
Romanov is not revealing the exact product and commercial indicators at the moment, but notes that the analytics show the main thing for him: there are players who are really «hooked» by the mechanics — they come back and continue to complete the levels. This is the main motivation to develop the project further.
In the latest update, the developer improved tooltips and feedback, added ad-free play and Game Center leaderboards, and continued to polish the game’s sound, animations, and dark theme.
A separate challenge is entering different markets, including Korea. According to Romanov, localization is not just about translating the interface: even a standard set of five screenshots for the App Store turns into dozens of materials for each language version.
The most valuable thing about a developer’s own product is full responsibility and experience: all decisions, from technical and visual to game mechanics, monetization and promotion, are interconnected, and it’s an opportunity not just to make decisions, but also to see how they affect the product and real people.
The application is free and available in the App Store: RiddleSum — Math Puzzle
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