Life In 19x19

so i'm sure someone has already thought of this. never the less i'll post it here.
for each turn, a player may either a) place a peice or b) stack as many adjacent stones onto it's nieghbor.
a stacked group is captured if two groups of greater size is stacked next to it.
the game ends when a group reaches a size equal to the number of empty intersections/2, or all enemy stacks have been removed.
the game "starts" only after each player has played at least once. (no passing)

example
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can become
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as another example:
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can become:
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but cannot become:
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phillip1882 wrote:the game ends when a group reaches a size equal to the number of empty intersections/2, or all enemy stacks have been removed.

Does size mean number of stones or stack height, or sum of heights of connected stacks?

i think number of stones in a single stack makes the most sense in this context.