How many VR Half-Life games have Valve released?
1
2
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
5
1
4
2
3
6
5
1
4
2
3
6
5
1
4
2
3
6
5
1
4
3
6
5
1
4
7
6
5
4
7
6
0
5
4
7
6
5
4
0
7
6
5
4
7
0
6
5
4
7
6
0
5
4
8
7
6
5
8
0
7
6
8
7
0
6
8
7
6
8
7
6
8
7
6
8
7
9
6
8
7
9
6
10
8
7
9
6
10
8
7
9
6
10
8
7
9
10
8
7
9
10
8
7
9
10
13
8
7
9
10
13
8
9
10
13
8
11
9
10
13
8
11
9
3 of them
10
1 (2017)
13
8
11
9
10
3 of them
13
8