This update from Apple will improve the functionality of this app. No new features are included.

New! Check Button gives you the option to remove incorrect paths.
Updated for iPhone X and iOS 11

Universal - play on any iPhone or iPad
Added support for iOS 10
Added support for iCloud, Game Center
New setting allows player to pick one of 3 coloring schemes for number rings
Improved drawing speed and clarity

Added 20 new, extra-large puzzles, bringing total puzzle count to 320.
Support for iOS 8
Support for iPhone 5, 6, 6+

Changes: zippier play, sound effects added.

Improved support for iOS4.x