A puzzle game you may well have seen before, each island has a number on it, which represents the number of bridges that will spring out from each island. There's enough information there for a smart player to link all the islands together, with the right number of bridges. Are you that smart player?
With a simple UI - sweep your finger in the cardinal direction from each island to build one bridge, two bridges (the maximum in each direction), or remove them all, you'll be able to chop and change the links between the islands quickly, as you look for the solution to advance to the next level.
With five hundred levels to work through, Hashi Puzzles is not going to be a quick game to finish, but it's well pitched, with a good difficulty curve that takes you through the smaller levels and teaches you the techniques for the later and larger levels.
There's nothing flashy about the game, there's nothing more than the core game-play, but as a 'b-list' gaming title I don't think it could do any better. Sometimes simplicity really is the best way forward.
Hashi Puzzles is a free download, pick it up from the AAWP App Directory.