In Metroid, you control power suit-wearing bounty Samus Aran as she explores the labyrinthine corridors of the planet Zebes. Her goal is to find and destroy the evil Mother Brain, who is looking to harness the power of the dangerous, titular creatures known as Metroids. The combination of side-scrolling action-platforming and exploration essentially created its own subgenre, and it remains one of Nintendo's most well-regarded franchises. Compared to its sequels, it's a little rough – there's no in- game map, many rooms look identical, and there are lots of hidden passages – but once you understand a few basic rules (bomb everywhere!), it becomes easily playable. Metroid was released solely on the Famicom Disk System in Japan. The main difference is that it uses a name entry screen and a save system, similar to The Legend of Zelda. This screen has a unique picture of Samus kneeling next to the name entry, which doesn’t appear in any other release. It also keeps track of how many times you've played the game, plus after beating the game, it features stacks of money bags next to Samus, indicating how long it took to complete it. The NES cartridge versions instead features a password function. The FDS release will always start you at the beginning of the game in Brinstar, while the NES version will restart you at the beginning of the area. After beating the game, you're also allowed to keep all of your energy tanks and missiles, essentially acting as a "New Game+," whereas this isn’t allowed in the FDS version. The NES game also has a stricter time limit to get the best ending (one hour vs. two). The password system allows for a bunch of unique cheat codes, too, including the famous JUSTIN BAILEY code. The ability to play without Samus’s armor was added for the NES version. There are some differences in the audio, as well. The sound effects, particularly the door opening sound, are stronger in the FDS version. The only other major difference is the "escape" theme right at the end of the game – it's longer in the NES version, and the FDS version has an annoying alarm sound effect. There are some minor gameplay differences, too – the NES version is a little glitchy, with off-colored background tiles in certain areas, and substantial slowdown. The enemies in the FDS game also display more erratic movement patterns. Finally, the battle against Mother Brain is more difficult in the NES version – there’s an extra piece of glass that prevents you from just standing next to her and attacking, requiring you to jump and aim through the opening in her jar.