Complex sentence: Released in 1979, Atari's "Adventure" contained the first hidden message in a video game to have been discovered by its players; the message is "Created by Warren Robinett", and was inserted by Robinett, the game's programmer.
Split into simpler sentences: Released in 1979, Atari's "Adventure" contained the first hidden message in a video game that game users discovered. The hidden message, "Created by Warren Robinett", was inserted by Robinett, the game's programmer.