I can't believe this thing exists. It's an Atari 2600 game released in 1989, 5 years after the release of the Atari 7800* and the NES. It's not a homebrew game; it was made by a toy company called Axlon, which was actually owned by Nolan Bushnell, long after he'd left Atari in the hands of Warner Communications.
What's more surprising is how deep the game is. The last game to approach this level of complexity was Dragonsmasher from Starpath, and that required a special adapter to let the 2600 use cassette tapes instead of its typical cartridges. I wanted to bring this video here because it kind of gently ties into what I was talking about with derivative works. At first glance, this game made me think of the Swordquest games or Adventure or even Haunted House, which had rudimentary exploration elements. Mark Bussler of Classic Game Room made the comparison to Zelda, though I think the game has more in common with Namco's Tower of Druaga or Falcom's Ys series, especially the way the character runs into enemies with sword extended. All these comparisons may sound like I'm putting the game down, but I'm not. In fact, though I called it a dungeon crawler, Secret Quest is firmly in the science fiction genre, with space stations standing in for castles. The object of the game is to explore the station and collect symbols to enter into a command console in the center of each station. Then, a timer appears, giving the player only a scant few seconds to backtrack though the station and get to a teleporter and escape the detonation of the station. If you thought I was going to say, "Just like Metroid." I wouldn't blame you, but you'd be wrong; it's actually more like Major Havoc, an arcade game from Atari released in 1983.
*) Interestingly enough, the 7800 was backward compatible with 2600 games, which I think stands as a real testament to Nolan Bushnell's business genius. The 2600 was easy to develop for, and it still had a solid install base between people who still held onto their 2600s and people who had 7800s as well. Seriously, don't mess with this guy.