TwentyFour!: http://appshopper.com/games/twentyfour
An Apple featured "Hot New Game".
Reviews:
"Mindbogglin g Never Was So Addictive" -- AppSmile
"TwentyF our! by Lucid Logic will not only entertain you for 15 minutes a
day, you may even learn something." -- AppModo
"a Great Workout for Your Brain" - AppCraver
"The 24 that stumped Jack Bauer" - AppSpotter
"With a balanced combination of mental arithmetic and problem solving
TwentyFour! is sure to stimulate your gray matter." - iPhoneAppRev ie