[failed verification][1][2][3] The game takes place on the planet Zebes, a large, open-ended world with areas connected by doors and elevators.

Ordinary enemies typically yield additional energy or ammunition when destroyed, and the player can increase Samus's carrying capacities by finding storage tanks and defeating bosses.

Once Kraid and Ridley have both been defeated, the player can shoot their statues to open the path to the final area and confront the Mother Brain.

The Space Pirates plan to replicate Metroids by exposing them to beta rays and then using them as biological weapons to destroy all living beings that oppose them.

While searching for the stolen Metroids, the Galactic Federation locates the Space Pirates' base of operations on the planet Zebes.

[13][14] The production was described as a "very free working environment" by Tanaka, who stated that, though being the composer, he also gave input for the graphics and helped name areas.

[15] Ridley Scott's 1979 horror film Alien was described by Sakamoto as a "huge influence" after the game's world had been created.

The development staff was affected by the work of the film's creature designer H. R. Giger, and found his creations to be fitting for the theme.

[16] Still, there were problems that threatened timely progress and eventually led Sakamoto to be "forcefully asked to participate" by his superiors, hoping his previous experience could help the team.

Sakamoto stated he figured out a way to bypass the limited resources and time to leverage existing game media assets "to create variation and an exciting experience".

Until then, most ability-enhancing power-ups like the Power Shot in Gauntlet (1985) and the Starman in Super Mario Bros. offer only temporary boosts to characters, and they are not required to complete the game.

The Western versions of Metroid use a password system that was new to the industry at the time, in which players write down a 24-letter code and re-enter it into the game when they wish to continue a previous session.

[citation needed] Tanaka said he wanted to make a score that made players feel like they were encountering a "living organism" and had no distinction between music and sound effects.

The only time a melodic theme is heard is when Mother Brain is defeated in order to give the victorious player catharsis.

[18] Officially defined as a scrolling shooter video game, Metroid was released by Nintendo for the Famicom Disk System in Japan on August 6, 1986.

[23] A stand-alone version of Metroid for the Game Boy Advance, part of the Classic NES Series collection, was released in Japan on August 10, 2004, in North America on October 25, and in Europe on January 7, 2005.

[40] Two years later, the magazine named Metroid the fifth-best game for the Nintendo Entertainment System in its Best of the Best feature, describing it as a combination of Super Mario Bros.'s platforming and The Legend of Zelda's exploration and character upgrades.

The website said that the combination of detailed sprites, original map designs, and an intimidating musical score "generated an unparalleled ambience and atmosphere that trapped the viewer in an almost claustrophobic state".

They noted that the Morph Ball, first introduced in Metroid, "slammed an undeniable stamp of coolness on the whole experience and the franchise", and they enjoyed the end segment after defeating Mother Brain, describing the race to escape the planet Zebes as a "twist few saw coming".

The review stated that the game was "still impressive in scope" and that the price was "a deal for this adventure" while criticizing the number of times it has been re-released and noting that it takes "patience" to get past the high initial difficulty curve.

[51] In GameSpot's review of the Virtual Console version, they criticized its "frustrating room layouts" and "constantly flickering graphics".

[53] The revelation of Samus being a woman was lauded as innovative, and GameTrailers remarked that this "blew the norm of women in pieces, at a time when female video game characters were forced into the role of dutiful queen or kidnapped princess, missile-blasting the way for other characters like Chun-Li [from the Street Fighter series] and Lara Croft [from the Tomb Raider series]".

Tanaka's score is an embodiment of isolation and atmospheric effect—one that penetrates deeply into the emotions.This view is echoed by GameSpot's History of Metroid, which notes how the "[game's music] superbly evoked the proper feelings of solitude and loneliness one would expect while infiltrating a hostile alien planet alone".