Develop rational number knowledge in engaging way! Semideus games are fun for all ages.

Master fraction and decimal numbers!

The Semideus School game is a really fun way to learn fraction and decimal numbers. By playing Semideus Matikka game, learners can improve their ability to understand rational numbers in multiple forms. The task of Semideus is to find the gold coins that a goblin has stolen from Zeus. On the way to Mount Olympos, Semideus has to chase the goblin, seek the coins, avoid traps, and crush math based enemies.

Attention! Semideus School is targeted for schools. In order for a student to play the Semideus School game, a teacher must create game access codes for students at

Game mechanics are integrated to following math concepts:

  • Numerator / Denominator notation
  • Rational number magnitude estimation, comparing, and ordering
  • Proper fractions, improper fractions, mixed numbers, decimal numbers
  • Equivalence and density of rational numbers
  • Adding, subtracting, multiplying, expanding, and reducing fractions

Learning analytics and effectiveness

The assessment of rational number knowledge is implemented seamlessly into the gameplay. Recent studies have shown that Semideus is very effective math learning tool and can reveal children's misconceptions about fraction and decimal numbers.

About the development team

The game has been developed collaboratively with learning experts: TUT Game Lab (Tampere University of Technology) and their international research partners. The game has been designed in research projects funded by Academy of Finland

Support and ongoing studies

Note that all Semideus games require internet connection. If you have questions about the game, contact us by email:

Participate to ongoing studies

Contact Kristian Kiili to participate ongoing research studies:


Lead game and instructional design

Kristian Kiili

Lead programming

Antero Lindstedt

Server side programming

Antti Koivisto, Kai Ojansuu


Juulia Virta and Eetu Suoranta


TUT Game Lab: Kristian Kiili, Arttu Perttula, Pauliina Tuomi, Antero Lindstedt

Stanford University: Keith Devlin

Special thanks to

Keith Devlin, Harri Ketamo, Venla Kiili, Mikko Koskela, Korbinian Mueller, Manuel Ninaus

Children’s Privacy Policy

This privacy policy discloses the privacy practices for the Semideus School and the Semideus Matikka games. The games are developed collaboratively with TUT Game Lab (Tampere University of Technology) and collected data is used for research purposes. We are dedicated to protect players’ privacy and handling any personal information we obtain from players with care and respect. This Children’s Privacy Policy aims to answer questions regarding to our privacy policies and principles with respect to children under the age of 13.

Description of the information that we collect about children

In order for a child to play the Semideus School game, a teacher (teacher refers also to the administrators of the school) must register each child (student) and obtain a game access code for him/her. In the registration process, a teacher will be asked to provide information about himself/herself, including an email address and the school where he/she is working. Thus, in order to play the game children do not provide or disclose any personal information that can be used to trace the exact person. Registration is not needed to play the Semideus Matikka game. If a player wants he or she can provide genre and age information.

  • We collect anonymous information such as earned coins, stars, and diamonds, playing accuracy, playing frequency, playing time, the use of game features, and IP address to help us improve our game and provide a better playing and learning experience.
  • Email address of the teacher who register students to the game is collected. The email address is not shared and is only used for delivering the game access codes to the teacher who will deliver the codes to the students.

How do we use the information that we have collected about children?

Non-personally identifiable playing data is used for improving the game and for research purposes. We may share aggregated, non-personally identifiable playing performance data publicly, including with student’s teacher, research partners (TUT Game Lab), or the press in order to, for example, demonstrate how our game is used and to study how effective the game is. The school under which the student registered has a possibility to use the data for assessment purposes.

If you are a child who is signed up for the Semideus School game, you should understand that your teacher, the school administrator, our game development team, and researchers from TUT Game Lab (Tampere University of Technology) can view the information associated with your account. There are no ads in our game and we do not share your information for marketing purpose. We do not currently have any social media services integrated into the game.

Children’s Online Privacy Protection Act

Our game comply with the Children’s Online Privacy Protection Act (“COPPA”). We don’t knowingly collect personal information from children under the age of 13 years old. If a user is identified as under 13 years old, we will not collect or use any personal information of this user and we will delete any information already received in a secure manner.

How long do we maintain anonymous player data?

Currently we do not regularly delete the anonymous player data that we collect. We analyze our database to identify player performance trends that can contribute to improving the quality of the game and to understand playing patterns that most effectively improve math proficiency.

Your access to and control over information

You may ask us to delete any information about you at any time by contacting us:


Our Privacy Policy may change from time to time and all updates will be posted on this page. This privacy policy was last updated on 14th March 2016. We will provide teachers with notice, using the e-mail that was used to register students, of any material changes in the way we intend to collect, use, and/or share collected information.

Questions or concerns about our Children’s Privacy Policy

If you need further assistance, please send an e-mail with your questions or comments to kristian.kiili(@)