This paper reports the first phase of an innovative, interdisciplinary, project that involves the creation of mobile games to promote the development of symbolic number sense (e.g. Jordan, Hanich & Kaplan, 2003) among young children aged approximately 6-8 years. The project draws on research from mathematical cognition, educational neuroscience and video game development, and represents a collaboration between researchers in these fields.

The main focus of the paper will be on the design of the game. Our aim with the design has been to achieve a number of things in combination:

1. The game's purpose is to promote children's fluency with number , particularly their ability to rapidly solve simple addition and multiplication problems
2. The game should be adaptive to individual learners' abilities  
3. The learning content should be integral to the objectives and mechanics of the game, not an 'add-on' (Malone, 1981; Habgood & Ainsworth, 2011)
4. The game should be fun to play, and should encourage long-term engagement
5. The game will provide a platform to research the role that different aspects of the game (e.g. reward schedules, amount of movement on screen, visibility of time pressure, and so on) have on children's learning

The qualities described in points 2-4 are derived from the growing literature on game-based learning. However, few games have been produced that adhere to these principles and even fewer have shown themselves to be effective in improving children's learning. Our working hypothesis is that the reason for this is not that the pronciples are flawed, but that adhering to them in one game is challenging; especially when the research/production team do not have direct experience of the different disciplines involved.

The core game mechanic requires players to tap numbers that fit a rule. There are two kinds of rule in the initial version of the game; players need to either select two numbers that add to a target (addition task), or they need to select individual numbers that are multiples of a target (multiplication task). Both tasks vary in difficulty according to the player's current level of knowledge and fluency with regard to the number task, and to the player's ability to intereact with the game mechanics (e.g. to tap a moving target). In this way the game will maintain an appropriate level of challenge; a key component of games that instil a sense of flow, identified as a marker of learning (Butterworth et al. 2011; Abuhamdeh & Csikszentmihalyi, 2012).

Meta-game components are employed in order to encourage long-term engagament. These are based on the 'free-to-play' games market, but rather than being designed to maximise value through in-game spending, they are designed to draw players back to the game to continue play. These components include sessioning mechanics and multiple levels of reward.

The initial version of the game will be used by the research team to further explore ways in which different aspects of the game design and mechanics do or do not promote learning. In order to do this, the game has been designed so that different aspects can be varied independently of one another. These aspects include:

• visibility of time pressure
• speed of movement of targets
• different forms of reward schedule

These variable aspects are informed by the educational neuroscience literature (e.g. Howard-Jones & Jay, 2016).  They have previously been investigated individually, but not in combination.

Abuhamdeh, S., & Csikszentmihalyi, M. (2012). The importance of challenge for the enjoyment of intrinsically motivated, goal-directed activities. Personality and Social Psychology Bulletin, 38(3), 317-330. Butterworth, B., Varma, S., & Laurillard, D. (2011). Dyscalculia: from brain to education. Science, 332(6033), 1049-1053. Habgood, M. J., & Ainsworth, S. E. (2011). Motivating children to learn effectively: Exploring the value of intrinsic integration in educational games. The Journal of the Learning Sciences, 20(2), 169-206. Howard-Jones, P. A., & Jay, T. (2016). Reward, learning and games. Current Opinion in Behavioral Sciences, 10, 65-72. Jordan, N., Hanich, L., & Kaplan, D. (2003). A longitudinal study of mathematical competencies in children with specific mathematics difficulties versus children with comorbid mathematics and reading difficulties. Child Development, 74, 834–850. Malone, T. (1981). Towards a theory of intrinsically motivating instruction. Cognitive Science, 5(4), 333-369.