Some of the music is taken from Half-Life 1 and 2!
Kelly Bailey (music composer of HL1 and 2) should have been credited in this movie....
At around 24 mins 30 seconds into the movie, you can hear a small music piece in the background that was made for the Antlion guard scene in HL2 and the missile base scene in HL1.
It's been played in parrallel with another music piece to make it sound original.
Did any other hardcore half-life fans notice this when first watching this movie?