I've been playing Go, a grid-based strategy game that dates back thousands of years, for more than three decades, and it's a game I enjoy a great deal. Unlike chess, which is often an all-or-nothing game of attack and defense, Go is about slowly-evolving strategies to surround the largest territory on the board. Each player, black and white, alternates placing stones on a board with a 19-by-19 grid. Building up territory, where the opposing player cannot get a foothold, each player attempts to enlarge his or her territory, and thwart advances and invasions by the opponent.

It's easy to learn the rules of Go; it's hard to become really good at the game. This is a game that computers can't yet defeat: the best programs can only defeat professional players with a handicap (Go has a handicap system where the weaker player gets to place from two to nine stones on the board at the start of the game).

If you want to play Go, or want to improve your game, there are a number of excellent iOS apps that can help you learn how to play and try to master the game. Here are the best ones. 

Getting started

You can start learning to play by playing games, or you can start by doing problems--situations set up to teach you certain moves, shapes, or ways of playing. To start learning the rules and the basics of the game, grab Igowin Tutor (free). This app contains a tutorial to teach you the rules, and lets you play nine-by-nine games to start. 

Once you know how to play, SmartGo Player ($3) is the best app to build your skills. You start out by playing on a nine-by-nine board. (While Go is generally played on a 19-by-19 board, it is also traditionally played on nine-by-nine, 11-by-11 and 13-by-13 boards with beginners.) SmartGo Player starts you out at its lowest level, and gets stronger as you do. As you increase in strength, you unlock the 11-by-11 and 13-by-13 boards.

You can use an auto-handicap system, or turn it off and take your chances. You can also change the amount of time the app thinks, from an average of 2.5 to 12 seconds per move. Even very strong players play Go on nine-by-nine boards to have quick games, and SmartGo Player will offer a challenge to players at the dan level. (Beginning player ranks are counted in kyu, from 30 to one; after that, ranks go from one dan to nine dan.)

Igowin Pro ($5) works in the same way, but offers nine-by-nine, 13-by-13 and 19-by-19 boards right off the bat. It changes strength as you increase in skill, offering handicaps when necessary, though you can choose your own strength and handicap settings. Each of these apps has its own playing style, and its own quirks. Igowin Pro only lets you undo one move; SmartGo Player lets you undo as many as you want. A good way to learn is to try a sequence and see if it works or not. Being able to undo, say, a half-dozen moves helps you learn from your mistakes. Igowin Pro can give you hints, however, which can also help you find the best moves.

Improve your skills

For beginners who've just learned the rules, problems are a great way to hone basic skills. Go Problems (free) has 227 problems to start out, and offers packs of problems as in-app purchases for $1 to $3 each. Some of these are standard problems, 500 in a pack, and some are collections of problems, such as the classic Igo Hatsuyo-Ron, or a set of problems created by the great player Go Seigen (Wu Qingyuan). You can go through the problems move by move, see where you've gone wrong, and find the correct moves to solve them.

Igowin Life ($3) also offers problems, many of which are "life and death" problems, where you have to figure out how to save or kill a group of stones. It has more than 2000 problems, and they're displayed at random, and in a random orientation as well, so you may see the same problem many times, to help you learn the moves it's highlighting. 

Another way of perfecting your Go skills is by watching and playing through the games of professional Go players. (The game is played professionally, mostly in Japan, China, and Korea.) SmartGo Kifu ($20) lets you do all this and more. (Kifu is the Japanese word for a Go game record.) In addition to providing the game-playing engine that's in SmartGo Player, with boards up to 19-by-19, SmartGo Kifu has more than 2000 problems, and an astonishing 81,000-plus games by Go players from more than a thousand years ago to the present. This game collection is the most impressive resource available, and includes the well-known (among Go players) GoGoD (Go Games on Disk) collection curated by John Fairbairn and T. Mark Hall.

You can view all the games by a specific player--for example, there are more than 2000 games by Cho Chikun, 1300 by Sakata Eio, 1100 by Takemiya Masaki, all 862 games by Go Seigen, and, of course, the 248 known games by Shusaku. You can choose to view a game at random, and play through it. And you can record your own games to analyze them later. You can also import any SGF files of games that you have, and you can even use it as a go board to play games with two players. 

Another way to improve your game is by reading Go books. There are books that teach you techniques, others that analyze and comment on games, and others which are collections of problems. One of the most important changes to the Go world was when Go Books (free)--by the developer of the SmartGo apps--was released. This app created a new format for Go books, which includes not only text and game diagrams, but lets you move through the diagrams as well. Diagrams in Go books often contain five, ten, even 20 moves, and it's hard to visualize them on paper. But with books in the Go Books app, you can play through diagrams one move at a time.  

Dozens of Go books are available as in-app purchases, including the classic Invincible, by John Power, which looks at the games of Shusaku, and which is considered to be the best book on the game of Go ever published in English. (Disclaimer: I was one of the reviewers of the Go Books edition of this book.) But you can also buy Janice Kim's Learn to Play Go series, the Graded Go Problems for Beginners series, and a number of Workshop Lectures by Yang Yilun. With the right amount of time, and the books available in this app, you could learn almost everything about the game.

And if you want to play against others around the world, check out PandaNet (free), a Go server app. Connect to the server and play with people of all skill levels, and even watch pro games and tournaments that are broadcast on the server. 

You've got a lot to choose from, but if you really want to study the game, SmartGo Kifu is the obvious choice. If you're a beginner, either Igowin Pro or SmartGo Player will get you started, and if you want to learn more, the Go Books app will help you build your own library of great Go books on your iPad.