Magic Square by Transum.org
A classic magic square puzzle in which pupils are asked to arrange 9 numbers in a 3×3 grid so that all the lines across, all the lines down and the two diagonals add up to the same number. this works on my elderly iPad as well as other tablets.
In a subtle twist the target number is not given, though in Level 1 the numbers are 1-9 as in the classic end of term brain teaser.
There are six levels in total with progressively more difficult numbers which should keep your Maths wizards buzy!
In addition there is an option for a random square and also an intriguing UNmagic square where the object is to AVOID any of the lines adding up to the same number.
All the puzzles provide instant feedback which, when errors are made, can be a great stimulus for discussion amongst the mathematical high fliers in your group.