Tic-tac-toe by Silverman

The game is played on the 4x4 board. One player uses X's tokens, the other one - O's tokens. Players move alternatively, and each player puts his token on the board with his turn. If a row of four identical tokens (either X's or O's) appears somewhere on the board - horizontally, vertically or on the upper-left-lower-right (!) diagonal - the player who started the game wins. Otherwise the second player wins. If four identical tokens appear on the upper-right-lower-left (!) diagonal, this is not a winning position and the play continues. (It is our correction of the original rules.)