Reversi
Place a disc so that it traps a line of the other colour between two of yours, and flip them. The most discs at the end wins.
How to play Reversi
How to play
Black moves first. Tap an empty square marked with a small dot: your disc must trap one or more of the computer's discs in a straight line (across, up and down, or diagonally) between it and another of your discs. Every trapped disc flips to your colour.
Passing and the end
If you have no move that flips a disc, you pass and the computer plays again. The game ends when neither side can move, usually when the board is full. The player with more discs wins.
Tips
Corners can never be flipped, so they are gold. Avoid the squares right next to an empty corner, which often hand it over. Early on, flipping fewer discs and keeping your options open beats grabbing as many as you can.
Opponents
Easy grabs whatever flips the most and makes beginner mistakes. Medium thinks a few moves ahead and knows the corners. Hard searches ahead, weighs the mobility of both sides and plays the last ten or so moves perfectly. Two players is pass-and-play on one device: Black and White take turns and the computer stays out of it.
Questions
Who moves first in reversi, and how does it start?
Black moves first. The modern setup starts with four discs in the centre: two black and two white, placed diagonally. Reversi itself dates from the 1880s; this diagonal start is the one used in tournaments today.
What happens if I can't move?
You pass automatically and the computer moves again. If neither side can move, the game ends and the discs are counted.
Can I play second?
Yes. Before your first move, choose Play second and the computer opens with black. Your choice is remembered for the next game.
How does the hint decide?
It runs the same search as the hard opponent for your side and tells you the facts about its move: corners, how many discs flip, and how many replies it leaves the computer. Near the end it can tell you the exact final margin with perfect play.
Is the hard computer beatable?
Yes, but it takes care. It looks several moves ahead and plays the final moves perfectly, so win the corners and edges early and keep your moves flexible.