Virus War
Two colonies grow across the squares towards each other: three actions a turn, each either placing your own mark or killing the enemy's.
Each player runs a colony: one in crosses, the other in noughts. A turn is three in succession, each of them a choice: put your own mark into a free cell, or declare an enemy mark killed.
A colony grows only from itself: a cell is when it touches — by a side or a corner — a living mark of yours. But there is a second road, and it makes the game what it is: a colony passes straight through enemy marks. Kill an enemy cell, and everything behind it becomes available.
Hence the way it is played. Three actions let you cut a corridor through an enemy line in one turn and come out behind it — while through your own killed marks nothing passes, so your colony stays vulnerable exactly where it has already been struck.
Rules of Virus War
The field
A grid of ten by ten cells. One player plays crosses, the other noughts.
The first marks go in opposite corners: the colonies start as far apart as possible.
A turn
A turn is three actions in succession. Each action is one of two things:
- growth — put your mark into a free available cell;
- a kill — declare an enemy mark in an available cell killed.
Killed crosses are ringed, killed noughts filled in.
Availability
A cell is available if it touches a living mark of yours horizontally, vertically or diagonally.
Availability also passes through killed enemy marks: a chain of them carries the colony onward as though they were its own cells.
Through your own killed marks availability does not pass.
What is not allowed
Placing a mark in an occupied cell. Killing what is already killed. Killing your own marks.
Making one or two actions instead of three — except where three legal actions do not exist on the field at all.
A whole turn may be given up.
End of the game
The game ends when one player has no legal action left: their colony has been destroyed or shut in. The opponent wins.
If both consider the position hopeless and both give up their turn, the game is drawn.
Notation
A turn is written as three coordinates in a row separated by dashes, one per action.
Worth knowing
Fields smaller than ten by ten are played, and the game is then shorter and harsher. Three actions to a turn is nearly universal but not the only count, and it should be agreed before the start. Where the colonies begin is set variously: opposite corners, or agreed cells.
Glossary of terms
- A killed mark
- An enemy mark struck out. It no longer grows its own colony but carries the other one through itself.
- An action
- One step within a turn. There are three to a turn, and each is either a growth or a kill.
- An available cell
- A cell touching — corners included — a living mark of your own, or reachable through a chain of killed enemy marks.