Conquer

Kepung Titik · the exercise-book dots game

Red to move

0RedYou

0BlueComputer

Dots captured

Opponent

Show capture chances

Rules

Players take turns placing one dot of their colour on any empty intersection of the graph paper. Red moves first.
Dots link up horizontally, vertically and diagonally with their eight neighbours.
Close an unbroken ring of your dots around one or more of your opponent's dots and they are captured. The loop is drawn in to seal the territory.
A ring with no enemy dot inside captures nothing and is not drawn — but if your opponent later drops a dot into that empty pocket, it is caught straight away.
Captured dots are dead: they can't form part of a ring. Nobody may play inside captured territory.
Rings can't use the edge of the paper. If you ring a territory that holds your own captured dots, they come back to life.
The game ends when the paper is full, or when you press End game. Most captured dots wins — or, if you choose Territory, the most enclosed points.

How the computer plays

Easy grabs any capture it spots and sometimes blocks yours, otherwise plays near the action.
Nets, not just rings. For every dot on the paper, Medium and Hard work out how many more dots it would take to ring it in. They see a net forming while it is still two or three moves from closing, and they build their own the same way.
The wide view. Before each move they also step back and look at the whole sheet: for every dot, the fewest points that would still seal it off from the edge — however far out the wall is being walked. A ring drawn patiently, ten points away, shows up while there is still a way out, and they defend at the gaps in your wall rather than filling in the inside of the net.
Double threats. They look for a single dot that would leave two of your dots one move from capture at once, with different points to close each. You can only block one, so they plug that point before you can play it, and play it themselves when you leave one open. A dot won for certain counts for more than a net that might close later.
Medium reads three moves ahead, its own, your reply and its answer, so it won't walk into a ring or leave one open for you.
Hard reads four moves ahead and weighs twice as many options at each step. It sets up double threats you can only block one of, and it cuts across diagonal links to take part of a chain.