public boolean u_play( int i, int j, int val ){
        int nval = -val;
        int i1 = i-1;
        while( i1>=0 && values[i1][j] == nval ){
            i1--;
        }
        if( i1>=0 && i1+1 < i && values[i1][j] == val ){
            // Valid play
            for( int k=i1+1; k<i; k++ ){
                values[k][j] = val;
            }
            return true;
        }
        return false;        
    }