Rules
In these rules, 'connected' will mean 'orthogonally connected', as will 'adjacent' and 'neighbor'. A 'group' is a number of connected like-colored stones. A single stone is a group by definition. In the rules placing a single stone on a square without like-colored neighbors will be called "starting a group", while placing a stone adjacent to a like-colored one is called "growing a group". The game starts on an empty board. White moves first, after which turns alternate. A player on his turn may either:

Start a new group, or ... grow any or all of his groups by one stone. A stone connecting two groups is considered to have grown both of them. However, if two groups are grown so that only the two newly grown stones touch, then the move is legal. Restriction At the end of a player's turn any two diagonally adjacent like-colored stones must be part of the same group. Turn order balance If, and only if, neither player has grown yet, then Red may grow any or all of his groups followed by a single stone placement, in the same turn.

Object
The object is to form a connected path of your stones between the opposing sides of the board marked by your colors.

Note:
Two groups may be connected by growing both of them, as long as both placements only touch one another, but neither placement is adjacent to both original groups. Thus two stones that are a knight's move apart, may be connected with two stones. Note also that the restriction rule prevents the possibility of growing more than two groups with a single placement, because then the player's previous move must have violated it.