Developer community

Developer spotlight: Yuuki Yamashita, Mifuku Works

This month, we chat with KaiOS’s first and only indie developer from Japan. Yuuki Yamashita is 36 years old and lives in the beautiful city of Fukuoka, famous for its ancient temples—such as the Tōchō-ji, home to a 10-meter wooden Buddha—and its modern shopping malls. 

In true Fukuoka style, Yuuki owns both an ultra-modern iPhone and a minimalist KaiOS phone. A full-time engineer, he builds KaiOS apps in his free time. He’s the creator behind Dungeon Slime and Multi Counter. Learn more about Yuuki below.

How does it feel to be the first KaiOS indie developer in Japan?

I’m proud to be the first KaiOS indie developer in Japan. I hope that the number of Japanese KaiOS developers will increase in the future. KaiOS is not so well known in Japan. If KaiOS devices start being sold here, the number of developers will increase.

How did you discover KaiOS?

I learned about KaiOS devices and how to develop KaiOS apps from overseas sites.

What inspired you to build a KaiOS app?

I had previously developed an app for Firefox OS. I started developing an app for KaiOS with that experience. Also, since there are no KaiOS app developers around me, I decided to be the first.

What challenges did you face getting started?

I had a hard time getting a KaiOS device. They are not sold in Japan, so I used eBay.

What’s your favorite part about developing KaiOS apps?

I like that KaiOS apps can be developed with HTML, CSS, and Javascript.

Are there KaiOS apps that you enjoy? Which ones?

AirshipCombat3D. I’m amazed that it’s possible to create 3D games on KaiOS!

Visit Yuuki’s website:

Connect with him on Twitter: @mikufuworks_y_k

Work at KaiOS

Work at KaiOS: Agnes Lo, HR manager, on how we recruit

Agnes Lo, HR manager at KaiOS for Hong Kong, the US, France, and remote staff in Africa, talks about recruitment at KaiOS and shares tips for job candidates.

What’s the best part about working for KaiOS?

Our mission. We get feedback from users thanking us for helping them connect to the internet. I mention this to candidates because I believe it’s what makes KaiOS special: When you work for KaiOS, you’re working towards something meaningful.

What’s the culture at KaiOS like?

We’re a Hong Kong-based company with offices worldwide. Even our Hong Kong office is very diverse: Half of the team members here relocated from other countries, so we have about 10 nationalities represented.

Our company culture is a mix of Chinese and Western. Western influence means a more flexible, open-minded environment for employees and an emphasis on communication. At the Hong Kong office, the team meets weekly to share updates on new products and projects. The Chinese influence can be seen in our attention to detail. I try to strike a balance between East and West.

Can you talk more about diversity at KaiOS?

We’re always working hard to make our recruitment processes even more inclusive. For example, we’re exploring new sources of hire, such as virtual networking events, to attract diverse candidates, especially women.

We’re also striving to remove human biases from the screening process by, for example, sending blind CVs to department heads so that they can’t see a candidate’s nationality, gender, or age.

What’s the recruitment process at KaiOS like?

We post jobs in different channels—job boards, our website, and LinkedIn. We also announce vacancies internally to get referrals. For hard-to-find positions, we actively source on LinkedIn.

When candidates apply, they get a confirmation email right away. It usually takes a few days for a candidate to know if they are moving forward or not in the recruitment process.

If they do move forward, we ask them to complete a take-home assignment. The type of assignment will depend on the position, but it usually consists of open-ended questions related to the job duties. There are no right answers; we just want to see how candidates think. For example, a developer might be asked to explain how they would go about fixing a bug.

If the candidate passes the test, we schedule interviews. Not just with team leads and HR, but also with team members, so that candidates can hear different perspectives and learn more about the position. Right now, these interviews are happening online because of the pandemic, but we usually do them in person with candidates who are local.

From application to offer, a recruitment process takes around three weeks. We aim to move as quickly as possible and to check in with candidates often. We do our best to provide a good experience even to the candidates that don’t end up moving forward, and we share feedback that can help them get hired in the future.

What kinds of people is KaiOS looking to hire?

People who are skilled, innovative, and eager to speak up and share their ideas.

We don’t hire based on educational background. We don’t ask that candidates have five years’ experience. We hire for skills, not certificates.

Some of our employees who work in tech don’t even have a background in tech—they studied Psychology, Marketing, or Engineering. But they were interested in coding, took courses, worked really hard, trained intensely for months. They proved that they were interested in the industry, taught themselves, and we hired them.

How did you get started at KaiOS?

Before starting as HR manager at KaiOS, I’d worked in HR and admin for 10 years. Many HR professionals focus on a specific niche—construction, finance, manufacturing. I worked for a company that made snowboarding and fishing equipment; for another that did waste treatment; at a financial institution; at TCL, a manufacturer company; and finally, in January 2018, I joined KaiOS, a software development company.

What are your current responsibilities?

50% of my job is recruitment. I was an HR generalist for a long time; now I’m focused on recruitment. My personality is outgoing and I like to communicate with people, so it suits me.

I also do HR and admin work. As I said earlier, we are organized and detail-oriented, so we have great review processes in place and standards for everything. My HR duties include doing performance appraisals, salary reviews, bonus releases, and communicating with employees. I believe in checking in with and supporting employees, not just enforcing company policies.

My admin work involves opening, registering, and staffing offices. I set up our offices in the US and France and their insurance plans, social benefits, and pension schemes. I had no previous experience with this, so I had to research, talk to other professionals, and learn about different jurisdictions. It’s all very complicated, especially in France!

How has KaiOS changed since you joined?

When I joined, there were only seven people in the Hong Kong office. Now we’re around 65 in Hong Kong, Paris, San Diego, and Africa. And we’re recruiting like crazy!

In all your time working for KaiOS, what are you most proud of?

Building a strong, talented team at our Hong Kong office. I was a little lost in the beginning. But slowly I was able to learn more about the skills we needed and the talent we were looking for and was able to grow a team from 7 to 65 hard-to-find employees, half of whom are not local. That’s been my biggest achievement in two years.

Interested in building the fastest-growing mobile OS? Check out our openings!

Industry insights

Increasing black representation with #Adtags’ Vimbayi Kajese

“I’m doing two lives on Wednesday,” says Vimbayi Kajese, “but I don’t know if they’re gonna like what I have to say.”

An expert on the topic of black representation, she’s the kind of public speaker that can both shake up an audience and give them goosebumps. The caveat? 

She’s radically honest. Whether she’s talking to top senior executives at the World Economic Forum or students at Stanford, she refuses to tone down her message. She’s an activist and her cause—saving black lives through representation—is too vital for that.

She admits that speaking out about racial injustice can be draining, especially in reaction to tragedies such as the killing of George Floyd

She has a lot to say, but she doesn’t want to be the only vessel for her message. She thinks that the other vessel could be her startup, #Adtags.

Dreaming up #Adtags

A smart feature phone user. Photo by Tunde Owalabi for KaiOS via #Adtags.

The idea for #Adtags came to her in a dream: What if there was a platform to connect brands and black content creators? Brands need authentic images of people of color. People of color need not just to be represented, but to have a say in how.

In her TEDx talk, Vimbayi reminds us that the representation of black people is often limited, negative, and unambiguous. 

“Black people aren’t granted nuance of feelings,” she told Tim Metz on Enabling Tomorrow. “They don’t show up in things that are happy; they don’t show up in things that are joyful; they don’t show up in things that have pride.”

She envisioned a platform where a black content creator could upload a photo of themselves and tag a brand. The brand would then have the option of buying the photo for commercial use. 

In that sense, #Adtags would work similarly to stock photo websites such as Shutterstock and Getty Images, where companies buy photos and creators get instantly paid. But that’s as far as similarities go. In a way, #Adtags is the “anti-stock photo” photo platform, filling in the gap for unique photos of people of color made by people of color.

The journey there

Although she did wake up with the user journey for #Adtags entirely mapped out, the idea for the platform didn’t come out of the blue. 

Vimbayi was born in Zimbabwe, but because her parents were diplomats, she lived all around Europe, Africa, and North America. Wherever she was, she was often the only black person, or the only Zimbabwean, in the room. “Representation is an issue that has always followed me. It’s a calling,” she says.

That calling was never as clear as when she joined China Central Television (CCTV) as their first black and African news anchor, speaking to an international audience of over 1 billion. Viewers who felt represented for the first time sent her messages saying she was an inspiration to them and a role model to their children. Because of her, the channel attracted unprecedented viewership from North America, Europe, and Africa.

Vimbayi as news anchor at CCTV.

After leaving CCTV, Vimbayi lived in different parts of West Africa, immersing herself in local cultures and discovering how black people in different countries perceived themselves. She saw the uniquely cool photos that her friends took and knew there was untapped potential there.

Finally, a stint in an advertising agency in South Africa showed her that advertising executives don’t always have a pulse on how young people engage with brands and products. And most of them don’t do a good job portraying black people in meaningful ways. 

Collaboration with KaiOS

Meanwhile, KaiOS had an urgent need for high-quality images of Nigerians using KaiOS phones. Tim Metz, Marketing Director at KaiOS, had watched Vimbayi’s TEDx talk and reached out to see if she would help.

Vimbayi and her partner, Nic Rawhani, liked the idea and accepted the challenge of connecting KaiOS to African content creators to produce the photos.

Seeing what a KaiOS phone can do. Photo by Ibunkun Akindele for KaiOS via #Adtags

Part of the job involved culturally interpreting KaiOS’s creative brief to make it resonate with diverse audiences in Nigeria.

The other was serving as a liaison between the photographers (or taggers, as they’re known in the platform) and KaiOS; negotiating terms and conditions; and creating the scenarios—all of it remotely and across multiple timezones.

“I couldn’t have done it without my strategic and creative advisor, Nic Rawhani; my legal team based in South Africa, headed by Chengetayi Mariti; and the help of my assistant Jemima Cortez, who beautifully executed scheduling in multiple time zones,” says Vimbayi.

The result was three sets of rare, beautiful images—the first showing people using smart feature phones to be available in an image library. One of them, by Nigerian photographer Emmanuel-King Itegboje, recently won a photo competition organized by The World Summit on the Information Society.

From Africa to Silicon Valley

Vimbayi recently relocated to California, where she’s in the process of transitioning #Adtags into a US-based company. She moved there to be around tech industry professionals and investors, the two kinds of people she is going to need to make her vision a reality.

Chatting. Photo by Tunde Owalabi for KaiOS via #Adtags.

Her vision: She wants 100 million pictures of people of color on billboards in the next ten years. She believes that exposure to images of people of color doing both ordinary and extraordinary things can help dismantle white supremacy.

Prior to the coronavirus outbreak, she was working from The Assembly, a women-centered coworking space in San Francisco. There, she spent a lot of time figuring out how to set up #Adtags to reflect her core values while complying with laws and regulations—not easy when you’re creating something entirely unique.

She knows for sure that she wants taggers to be well compensated. She also wants them to have the creative freedom to portray themselves authentically.

Most of all, she wants more images of black people and people of color everywhere. To her, it’s a matter of life or death.

Liked #Adtags’ mission? Check out their website and subscribe for updates.


Industry insights

The ultimate guide to smart feature phones

They’re not smartphones. They’re not regular feature phones, either. Perhaps the best way to describe “smart” feature phones is that they’re feature phones with internet and apps.

On feature phones, all you can do is make calls and send texts. Smart feature phones, on the other hand, offer advanced functionalities: beyond calling and texting, you can read the news, play games, connect with friends on Facebook, and more.

But if these devices connect to the internet, what makes them different from smartphones? What features do they have? And, in a world ruled by smartphones, why do feature phones, however smart, matter?

In this guide, we’ll answer these questions and more.

What’s a smart feature phone?

Smart feature phones are a hybrid of feature phones and smartphones. They look and feel like feature phones, but have smartphone functionalities, including multimedia and internet capabilities.

Alcatel Go Flip 2, one of the earliest smart feature phones enabled by KaiOS


Because they are nontouch devices with little memory, smart feature phones cost less to produce than smartphones. Not having large touchscreens also makes them more durable and resistant to impact, which means they last longer than smartphones.

The components of smart feature phones include:

  • Battery
  • SIM card slot
  • SD card slot
  • Camera 
  • USB port
  • Microphone & speaker
  • Flashlight

Additional components might be available depending on the phone model.


Like smartphones and feature phones, smart feature phones run mobile operating systems (OS).

The mobile operating systems of smart feature phones are lightweight to adjust to the limited random-access memory (RAM) in these devices, which can be as low as 256MB.


Though smart feature phones may look retro, they have the essential features you’d expect from modern devices, including:

  • Wi-Fi, 3G/4G/LTE, VoLTE
  • GPS
  • Bluetooth
  • Voice-user interface
  • App store
  • Over-the-air updates
  • Calendar
  • Clock
  • Email
  • FM radio
  • Ringtones

Additional features, such as WhatsApp, Facebook, YouTube, and Google Assistant, might also be available depending on the phone model.


Despite their small screens and keypad navigation, smart feature phones aren’t difficult to use. UX designers are continuously searching for ways to create more screen space and optimize navigation on smart feature phones.

Production of smart feature phones

Mobile OS development companies partner with local carriers and original equipment manufacturers (OEMs) to bring smart feature phones to life.

They lay out the plan for what’s possible on smart feature phones, leaving carriers and manufacturers to decide how to execute the plan to best meet the needs of their target customers.

A mobile OS’s support for features isn’t a guarantee of their implementation. For example, although KaiOS supports near-field technology (NFC) for payments, manufacturers might choose to leave out this feature in some KaiOS devices.

Smart feature phone types

Smart feature phones can be divided into four types:

  1. Candy bar phones
    Candy bar phones (also known as bar phones) have this name because they’re roughly the same shape and size of a chocolate bar. They’re compact mobile phones with a small screen and keypad on a single face. The most widely available and affordable smart feature phones are candy bars.
    Examples: TNM Smart 4G, Altan K26
  2. Rugged phones
    Often encased in shock-absorbent rubber, rugged phones are known for their near indestructibility, which makes them ideal for manual workers or people who practice outdoor activities. Some are military standard 810G (MIL-STD-810G) compliant, which means they go through a series of tests that put them up against shock, vibration, humidity, heat, cold, humidity, and even gunfire shock to ensure that they’re “combat-ready”.
    Example: Nokia 800 Tough, CAT B35

    CAT B35, a rugged smart feature phone that is dust and water proof
  3. Keyboard phones
    Keyboard phones come with a full QWERTY keyboard. They’re sought out by people who use their mobile phones to type emails and other longer messages and prefer a physical keyboard over an on-screen one. QWERTY keyboard phones can be candy bar or slide phones. If they’re candy bars, the keyboard shares the same surface area as the screen; if they’re slide phones, or slider cell phones, the keyboard slides out from under the screen.
    Example: JioPhone 2
  4. Flip phones
    Flip phones are foldable. Their clamshell design makes them shorter and narrower than other types of devices and protects the keys and display from damage and unintended use. The interface components on flip phones tend to be larger than in other types of mobile devices.
    Examples: Nokia Flip 2720, Alcatel GO FLIP 3

Smart feature phone users

Smart feature phones aren’t for everyone, but meet the needs of niche customers, including:

  • Low-income individuals priced out of the smartphone market
  • Older adults with a preference for simpler interfaces and physical keyboards
  • Manual laborers and people who practice outdoor activities
  • Organizations that need simple, affordable internet-enabled devices for work
  • Individuals looking for a companion phone

There’s a growing demand for smart feature phones worldwide, especially in emerging markets.

Importance of smart feature phones for digital inclusion

With prices starting as low as $11 USD, smart feature phones are crucial for advancing digital inclusion. In India, the JioPhone has helped hundreds of thousands of people get connected.

In addition to being affordable, smart feature phones are also more accessible to first-time internet users, including those who can’t read or write.

For these reasons, they are becoming increasingly popular even among those who have been traditionally excluded from the digital world, such as farmers in remote villages in Africa.

KaiOS and smart feature phones

Built by KaiOS Technologies, KaiOS is a web-based mobile operating system developed exclusively for smart feature phones. Over 100 million smart feature phones in over 100 countries worldwide run KaiOS.

In addition to developing the OS that makes affordable internet-enabled devices possible, KaiOS Technologies also works to increase digital literacy and access to meaningful connectivity around the world.


Smart feature phones look and feel like feature phones. But unlike average feature phones, “smart” feature phones connect to the internet and offer access to apps.

Simple, durable, and inexpensive, these hybrid devices cater to niche customers, including low-income individuals in emerging markets.

Their affordability makes them essential to closing the digital divide.

Explore KaiOS devices

Developer community

An interview with Spyro Merianos, from BlackSheep Games

Spyro Merianos, BlackSheep Games founder

BlackSheep Games founder Spyro Merianos has 43 games in the KaiStore. He should hit 50 by early July. In this interview, the developer behind Angry Chicken, Pyramid Escape, and Chess shares what he’s learned from building all of these apps—including how to keep players engaged and coming back for more—and tells us how he manages to be so productive. Spoiler: it involves waking up at 3 am every day. Read on to find out more.

Is it true that you wake up at 3 am every day? What’s your routine like?

I wake up at 3 am because there’s more silence and I’m better able to focus. My schedule is as follows: I wake up at 3 am, sit at the work computer after 15 minutes of personal hygiene and coffee preparation, and work on the current game project until 7:15 am. Then it’s time to answer emails and have a snack for 15 minutes or so. After that, I continue with game development until around 12:30 pm, when I pause for lunch. Usually, I sleep from 1 pm to 2:30 pm. Then I do more game development until 5:30 pm and answer emails. I eat dinner and either do other activities or more game development, depending on the day, until around 9:00 pm when I start getting ready to go to sleep.

That’s quite an impressive schedule! You’re also pretty strict with your phone use.

I’m actually using a smart feature phone as my daily driver phone. Before, I was using smartphones exclusively for calls since I don’t use any mobile apps. Now I’m doing everything from a desktop computer.

No apps?!

There’s no need to, for my very own personal use case. If I can do a task on my computer, I’m not going to download an app to also do it on the go. I have these two circumstances separated, so when I’m at the computer, which is most of the day, I do all the work that needs to be done at that time. When I’m outside for some other activity, I focus on that activity exclusively.

Do you think you’re the exception, or do you see more people choosing to use smart feature phones as a way to have fewer distractions?

I’m definitely not the exception. Lots of people are trying to use smartphones less and escape the 24/7 distraction of social media. I believe smart feature phones are a great tool for that.

So how did you get started building apps for KaiOS?

I was invited by a KaiOS team member through a developer marketing campaign in late 2019. After checking out the platform, I decided to try it out because I really like HTML5.

Screenshot of Angry Chicken

What was your first KaiOS app? How have you evolved since then?

The first game that I used internally to test the platform was Angry Chicken. After I successfully ported it to KaiOS, I decided to focus on KaiOS as my primary development platform. I got better and more efficient the more I created games – with each one, I learned more about the OS and the user patterns.

Can you tell me more about these user patterns?

I’ve found that users tend to spend more time on a game if it has levels and less time if the game is score-based. Also, KaiOS users spend more time in general inside games compared to users on other platforms. That gives us an incentive to increase the scope of games.

Screenshot of Chess

What’s your most popular KaiOS app?

The most popular game, in terms of numbers, is a chess game you can play with either AI or with a friend using the same phone. The board and pieces change color each time the games resets, which gives a sense of novelty each time you play.

Why do you think it’s so popular?

I improved it based on user feedback. That really helped with retention.

How did you get user feedback and what changes did you make?

For the chess game, I had some people reach out to me and tell me that having a way for single players to play against the AI would be best. Since KaiOS doesn’t have ratings or a comments section yet, I mainly base myself on user stats to determine behaviors and make improvements. I’ve found that simply optimizing the games to run faster helps increase retention.

What advice do you have for developers who are just getting started?

Given the simplicity and the technical limitations of smart feature phones, I recommend keeping the scope of apps smaller than what they are used to in other platforms. And checking out the official documentation and videos.

What does nobody tell you about building apps for KaiOS?

That you reach users who are connecting to the internet for the first time. You have the unique opportunity to provide them with entertainment and knowledge and enhance their lives. That your games and apps actually make a big difference for some of these users.

Interested in building your own KaiOS apps? Head on over to the Developer Portal to get started, or get in touch with Asis at for any questions you might have.

Don’t forget to subscribe to our “Developer Updates” to get the latest news on development in the KaiStore.

Developer community

An interview with KaiOS developer Gabriel Rotaru

Through his software development company, Cypien, 25-year-old Gabriel Rotaru has built 30 KaiOS apps, including Guess the Logo, Hangman, Sliding Puzzle, and Trivia Challenge. And he’s just getting started. Learn more about Gabi and his hopes for KaiOS in the interview below.

How did you first hear about KaiOS?

I don’t remember when and where I first heard about KaiOS, but I know it was somewhere around August 2019. The value proposition of “connecting the next billion” really resonated with me.

When did you build your first app?

In September 2019, I bought a Nokia 8110 4G – the infamous “banana phone.” At that time, there were very few KaiOS apps and I thought, hey, I should try and build some. Today, I have over 30 apps in the KaiStore.

What were your challenges starting out?

KaiOS apps are web apps and my skills in this area were rusty, to say the least. That was a bit discouraging.

When I did find the motivation to build my first app, I discovered that there was no documentation, the developer console had bugs, and the community around the topic was small. Even installing the official sample app on my test phone was hard. I almost gave up.

Apps developed by Gabriel; Sliding Puzzle, Guess the Logo, and Trivia Challenge.

Fortunately for me, a KaiOS team member, Asis, reached out to me. With his help, I ended up building a trivia quiz app which I launched last November. It only got a few dozen users per day, but it was enough to motivate me to build more.

What’s it like building KaiOS apps today?

A lot easier. The KaiOS ecosystem is more mature. The official team is working hard to improve developer tools and bring in users to the platform. Communities dedicated to KaiOS are also getting bigger – there’s a subreddit with 1.3K members and developers asking and answering questions on Stack Overflow. So yeah, definitely better and improving.

Strongly believing in something makes you focus and be more productive.

You mentioned building over 30 apps! What types of apps do you build?

I’ve built utility, entertainment, lifestyle, and fitness apps. Also games. I don’t lean towards a specific category. Anything goes, as long as it’s interesting to a large number of users.

How do you come up with ideas?

I think of apps I’m using on my Android phone that aren’t on KaiOS yet. Then I create basic wireframes, plan the implementation, and get started.

Is it hard juggling your projects for KaiOS apps with your full-time job?

I struggle with it all the time, but I try to remember that everyone has the same number of hours, even Elon Musk. And he gets a lot done!

I try to be as efficient as I can with my time by avoiding meetings and automating my repetitive work. Being more efficient means I get more time to do the things I love and believe in. Strongly believing in something makes you focus and be more productive.

Thanks for believing in KaiOS.

Sure. This might sound cheesy, but I really think KaiOS can help people from disadvantaged areas. Imagine how their lives could change with access to information, courses, encyclopedias, ebooks!

KaiOS is sealing new partnerships, launching new devices, and bringing in more developers and users every day, so I’m very hopeful. The future looks bright for KaiOS.

What are you working on now?

I’m working on several new apps. Some of them are almost finished – you might see something new from me over the next few days.

Interested in building your own KaiOS apps? Head on over to the Developer Portal to get started, or get in touch with Asis at for any questions you might have.

Don’t forget to subscribe to our “Developer Updates” to get the latest news on development in the KaiStore.

Developer community

An interview with Victor Lee, from Kibi Games

Editor’s note: Kibi Games caught our attention because they tried something new. Most KaiOS developers build their apps to fit the full screen of a smart feature phone (240×320). They then monetize through ads that either take up the full screen or appear as rolling banners.

Kibi Cross takes up 80% of the screen and has a rolling banner ad running the whole time. Because of this, it has gained a good number of ad impressions. Also, if you restart the app, you have to see the ad again, which has helped increase the clickthrough rate.

Learn more about Kibi Games, Kibi Cross, and strategies for creating successful mobile games below.

Who’s behind Kibi Games?

Kibi Games is Mala, the designer; Pn, the artist; and me, the programmer. We are all Taiwanese and based in Taipei. We’ve been making games for over ten years.

What’s the story of Kibi Games? Who started it, when, and how?

We’ve known each other for years and worked together in different companies. Three years ago, we teamed up for Adventure Jam, which challenges you to build an adventure game in two weeks. After Adventure Jam, we kept on making games.

What’s a day at Kibi Games like? Do you have an office?

It’s usually pretty busy. We share an office with friends, so besides working on our projects, we sometimes help them with theirs.

Victor the programmer as a husky, Mala the designer as an ape, and Pn the artist as a quail.

Do you work exclusively with mobile games?

We don’t like to limit our platform options. Our primary project right now is on PC. We’ve built web games and console games. We’ve built for Windows, Linux, Mac OS X, iOS, Android, PS3, and Nintendo Switch. If a platform is appropriate for a game, we’ll give it a try.

What made you decide to build on KaiOS?

We were choosing side projects to work on to increase our visibility and maybe even our revenue. Since we’re a small team, there’s always one primary project we’re all working on together. We don’t have a lot of energy or resources left to dedicate to other large projects. We’d heard about KaiOS and smart feature phones, about how they have small screens and limited performance. We figured that these limitations would help us create games. Since we wouldn’t need to invest a huge effort to build one, we decided to give it a go.

Did you face any challenges? Which?

We build 2D games with GameMaker Studio, a game engine that exports html5 builds via its web module. We couldn’t find any articles or posts about developing for KaiOS with GameMaker, so any issues or questions we had about HTML5 and KaiOS, we had to sort out ourselves.

Mountain’s Spirit is Kibi Games’ newest project

How did you get the idea to build Kibi Cross?

After we launched our first KaiOS game, Treasures Of Pirates, we got helpful analytics and feedback. We realized it was better to create static games, like puzzles, and that they needed to be fun, playful, and kind of addictive. That’s why we chose the nonogram as a core gameplay to create Kibi Cross.

Kibi Cross is pretty popular right now…

Since it was published on December 17, 2019, it’s gotten around 6 million impressions and 13,000 ad clicks.

Why do you think it’s so popular?

I think the gameplay of the nonogram is very solid, like 2048 and Tetris. It’s challenging and fun. We added many levels to it, too – there are about 300. And there’s the “World’s Best” mode, where players submit their scores to our global leaderboard to compete with one another. All of this makes the game more enjoyable to play.

Kibi Game’s Kibi Cross has a “World’s Best” mode. Users submit their score to compete with other users globally.

How do you promote Kibi Cross?

We self-promote like this: all our games read a JSON file we put on our website. When we have a new game out in the KaiStore, a “News” button appears in the title of our games, and players can get more info and images. (More on their strategy below.)

What advice do you have for developers wanting to build apps on KaiOS, especially games?

We suggest going to the KaiOS Webstore to check out all apps in the category you’re going for and exploring similar apps. This will help you create something special. If possible, get a 256MB KaiOS device. The QA team reported that there are issues that only happen on 256MB KaiOS devices. If you can’t get one, you’ll have a little trouble debugging. That’s our case, since we can only buy the Nokia 8110 4G (512 MB) here.

What are you launching next?

The project we’re working on now is called Mountain’s Spirit. It’s a PC game inspired by the Taiwan Black Bear. Our goal is to complete and launch it this year. We’re also sketching our 3rd KaiOS game project.

Interested in building your own KaiOS apps? Head on over to the Developer Portal to get started, or get in touch with Asis at for any questions you might have.

Don’t forget to subscribe to our “Developer Updates” to get the latest news on development in the KaiStore.

Developer community

An interview with KaiOS developer Valeriy Skachko

A former teacher in Lugansk, Valeriy Skachko had to leave his home and his job when war broke out in eastern Ukraine. Four years later, he’s an accomplished freelance developer based in Ivano-Frankivsk. He built 21 apps on KaiOS just last year,  ranging from a period tracker to a talking hamster. He also runs, the largest and most popular website about KaiOS in the Russian language. Learn more about this KaiOS enthusiast and prolific app developer.

So, tell us how your story with KaiOS began.

In 2018, I read about the Nokia 8110 4G. That’s when I learned about KaiOS. I studied the system and fell in love with it. Hearing that KaiOS wanted to expand the capabilities of feature phones and modernize them inspired me. I decided to create apps to help KaiOS users take full advantage of their smart feature phones. I wanted to contribute to the KaiOS mission.

When did you start building on KaiOS?

I built my app in April that year (2018). There was very little documentation at that time, but I was determined to build at least one app, so I sent several emails to Support until they connected me with Harshdeep Vaghela, who helped me with the first steps in the development process (he still helps me a lot, so thanks, Harsh!) Nowadays, it’s much easier. There’s plenty of documentation on the Developer Portal and the support team replies much faster.

What do newbies most struggle with when starting to build on KaiOS?

The first problem is that, to create a KaiOS app, you need a KaiOS device. The simulator isn’t enough to fully test an app. The second problem is that most developers create apps for touchscreen devices, so they have a hard time rewiring their brains to build for non-touch devices. Third, you’re dealing with small screens, so you have to be mindful of that.

Any tips or advice you can share?

My advice is research, research, and research. You can find lots of info at MDN Web Docs (most docs for Firefox OS also work on KaiOS). Ask questions in forums like this one. And buy a KaiOS device.

Screenshot of Sun Compass, an app by Valeriy Skachko
Sun Compass, an app by Valeriy Skachko

You’ve built 23 apps so far. Are they similar in any way?

I see the phone as a means of communication and as an assistant in life, so I try to create apps that are useful. I’m not very interested in games, for example, although I would consider creating an intellectual one.

Which of your apps is the most popular? Which one are you most proud of?

My most successful apps are World Radio and Night Clock. The one I’m most proud of is World Radio – it has online radio stations from all over the world. I try to add new radio stations every week. Right now, it has stations from 37 different countries!

World Radio, one of Valeriy’s favorite apps
Voice Recorder, another one of Skachko’s creations

Cool. So how do you get ideas for apps? Do you already know what you’re building next?

I ask myself what I miss on a feature phone – then I go and build that. I also get ideas from comments made by users.

As for what I’d like to build next, I’d love to make Bluetooth chat, and more reference books, available. I’d also like to expand the functionalities of some of my existing apps (World Radio, for example).

Do you have a goal in mind, such as building 50 apps by the end of the year?

Not really. My goal isn’t to create as many apps as possible. I’d rather create one good app than build five bad ones in the same amount of time.

Besides KaiOS, what else are you into?

I love traveling with my wife and daughter. I try to visit one new country every year. Last year I was in Georgia; before that, I was in Israel; before that, Turkey, and so on.

Interested in building your own KaiOS apps? Head on over to the Developer Portal to get started, or get in touch with Harshdeep at for any questions you might have.

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