It's a marble placement, turn-based strategy game. The goal is to be the first player to place five marbles in a row. The rows can be vertical, horizontal, or diagonal. The game is a bit like Connect Four, but with a twist.
The board is made up of four 3x3 sections. Each section twists in two directions, clockwise or counter-clockwise. After you place a marble in an empty slot, you must turn one of the sections a quarter turn. You can turn any section, regardless of marble placement. You keep filling the board until there is a winner or there's a draw.
If you click on the instruction tab, you will see an animation showing you how the game mechanics work. The instructions are also available 20 different languages.
Analysis: Pentago is simple to play, infuriatingly hard to play well. The movement of the sections is what makes the game so challenging. You have to anticipate where your pieces will be after a turn, and any planning ahead usually gets quickly scuttled by your opponent. Turning the board of course can help you or hurt your opponent. You could spend several moves fighting over which direction one section gets turned. Your line of five marbles will stretch onto two or three of the sections. The three section wins are quite mind boggling, and the computer certainly knows how to accomplish the advanced tactic.
The graphics are rudimentary, but the gameplay works smoothly. The design is clean and simple. You don't really have to know the rules to start to play online.
Unfortunately the two player mode is for taking turns on the same computer. You can't play against others over the net. There is a way to challenge your friends through email, so you could make the turn-based game somewhat interactive.
This brain twister strategy game takes concentration, and possible hair pulling. It's challenging and fun to play, even though I usually lose. You can track down a wooden board if you want to play the tactile version, and there is even a deluxe version with four colors and nine sections.
For those of you who want to delve into the strategy and tactics further, there is comprehensive PDF strategy guide available.