How many VR Half-Life games have Valve released?
1
1
1
2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
4
3
1
2
4
3
1
2
4
3
1
2
4
5
3
1
2
4
5
3
1
2
4
5
3
1
2
4
5
3
1
2
4
5
3
1
2
4
5
3
1
2
4
5
3
1
2
4
0
5
3
1
2
4
5
0
3
2
4
5
3
4
5
3
6
7
4
5
6
7
4
5
6
7
4
5
6
7
4
5
6
7
4
5
6
7
4
5
8
6
7
5
8
6
7
5
8
6
7
5
8
9
6
7
8
9
6
7
8
9
10
6
7
11
8
9
10
6
7
11
8
9
10
6
7
11
8
9
10
6
7
11
8
9
10
6
7
11
8
9
10
6
7
11
8
9
10
6
7
11
8
9
10
6
7
13
11
8
9
12
10
6
7
13
11
8
9
12
10
11
2+
112
112
2+
3+
1+
112