How many Portal games are there?
2
3
3
2
3
2
3
2
3
2
3
4
2
3
4
5
2
3
4
5
2
3
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
2
3
1
4
5
6
2
3
1
4
7
5
6
2
3
1
4
7
5
6
2
3
1
4
7
5
6
2
0
1
4
7
5
6
2
1
4
0
7
5
6
1
4
7
5
6
0
1
4
7
5
6
0
1
9
4
7
5
6
8
1
9
0
7
5
6
8
1
9
7
6
0
8
1
9
7
6
8
0
1
9
7
6
8
9
0
7
6
8
9
7
6
8
9
7
6
8
9
7
6
8
9
7
6
8
9
7
10
6
8
9
7
10
6
8
9
7
10
8
9
11
10
8
13
9
11
10
8
13
9
11
10
8
13
9
11
ten
10
8
13
ten
3 games