Sumquest

Sumquest is an addition based game. It has been created to boost mental maths ability for all ages.

Mathematical games are ‘activities’ which involve a mathematical challenge, are governed by a set of rules and have a clear underlying structure, normally have a distinct finishing point and have specific mathematical cognitive objectives (Way, J (2013) “Learning Mathematics Through Games Series” on the University of Cambridge NRICH website).
Source

Hunt's link is its official website, its app is available for ios and Android. Sumquest also has Kickstarter Campaign.