The competition-independence game, as introduced by Phillips and Slater, is
played on a graph by two players, Diminisher and Sweller, who are taking
turns in choosing a vertex that is not in the closed neighborhood of any of
the previously chosen vertices. The goal of Diminisher is to minimize the
(maximal independent) set of chosen vertices at the end of the game, while
Sweller wants just the opposite. Assuming that both players are playing
optimally according to their goals, two graph invariants arise depending on
who starts the game. In this paper, we introduce a variation of the game in
which players are allowed at any stage in the game to use an alternative
move called prevention. That is, a player can decide that in his/her move
he/she will mark (not choose!) a previously unplayed vertex x by which x is
prevented to be chosen during the rest of the game; in particular, x is not
in the final set of chosen vertices. Given a graph G, and assuming that both
players play optimally according to their goals, ?Id(G) (resp.?Is(G)) denotes
the size of the set of chosen vertices in the competition-independence game
with prevention if Diminisher (resp. Sweller) moves first. By using the
Partition Strategy we prove that for any positive integer n, ?Id(Pn) = [2n+3/6] and ?Is(Pn) = [2n+4/6]. While it is not hard to establish the general
bounds, 1 ??Id(G) ? [n/2] and 1 ??Is(G) ? [n/2], we characterize the
classes of (connected) graphs G that attain each of the four bounds.
Finally, a close connection of the new game with a version of the coloring
game called the packing coloring game is established for graphs with
diameter 2, and several open problems are posed.