This is actually a teaser trailer for an upcoming teaser trailer for a fictional CGI movie telling the story of Half-Life and Half-Life 2. So a trailer for a bigger trailer - he isn't making an actual movie, you understand. That said, it's stunning. Embedded below:
It's very well made by a chap called Marco Spitoni, who's been making CGI shorts for years. You might recognise this metal dragon hunting short he made that did the rounds a while back, for example. There sure are a lot of people making teaser trailers for Half-Life 2 fan projects. Who do you think will actually finish theirs first?