How many games are in the Portal series?
2
3
3
3
3
3
4
3
5
2
4
3
5
2
4
3
5
2
4
3
5
2
4
3
5
2
4
3
5
2
4
3
5
2
4
3
5
2
4
3
5
2
4
3
1
5
2
4
3
1
5
2
4
3
6
1
5
2
4
3
6
1
5
7
2
4
3
6
1
5
7
2
4
3
6
1
5
7
2
4
6
1
5
7
2
4
6
1
5
7
2
4
8
6
1
5
7
2
4
8
6
1
5
7
2
4
8
6
1
5
7
2
8
6
1
10
7
9
8
6
1
10
7
9
8
11
6
1
10
7
9
8
11
6
1
10
7
9
8
11
6
1
10
7
9
8
11
6
1
10
7
9
13
8
11
6
1
12
10
7
9
13
8
11
6
1
12
10
7
9
13
8
11
6
1
12
10
7
9
13
8
11
16
6
12
10
7
9
14
13
8
11
16
6
12
10
7
9
14
13
3 games