Metal Storm is a side-scrolling platforming shooter developed by Tamtex and published by Irem, released for the Nintendo Entertainment System in 1991. Known as Juuryoku Soukou Metal Storm in Japan (which loosely translates into "Gravity Armor"). The game introduced a gravity reversing mechanic, which the player uses to solve platforming puzzles.
The plot revolves around a giant laser cannon that is being controlled by aliens who intend to use it to destroy Earth. The main protagonist of the story is a large robot operated by a man on Earth, who must infiltrate the alien home world in order to stop the destruction of Earth. Eventually, after breaking through the alien planet's defenses, the player must sacrifice his robot in order to destroy the alien home world.
These story elements are only revealed in the instruction manual for the game, and the very limited ending. The game lacks any in-game dialog, cut scenes or non-enemy NPCs.
The key mechanic in Metal Storm is the ability to alter gravity, switching from the ceiling to the floor (when switching, all enemies in the stage are also flipped). Certain enemy types also use the Gravity mechanic as part of their attack.
The game is divided into six stages. Each stage is broken up into two sub-portions. Reaching the end of the first sub-portion provides the player with a checkpoint. If the player dies in the second sub-portion, they start over at the checkpoint. The difficulty of the game is focused around pattern memorization, similar to the most recent Mega Man releases.
The game features several different weapons, each of which alters a certain gameplay mechanic.
The Gun item effects the shooting mechanic. When equipped, it gives the player's gun a wider, more powerful beam. It also has the ability to pass through certain walls, allowing the player to damage an enemy without risking themselves.
The Fireball item affects the Gravity Reversal mechanic. This item makes the player invincible whenever they flip gravity. It allows the player to rocket indestructibly from the floor to the ceiling, and back again. With this item equipped, enemies that run into the player while are are falling back and forth will take damage.
The Shield item effects the player's defense. The shield faces the same way the player points their weapon and it covers one quarter of the player's body. It prevents damage to the player from most attacks, although physical attacks and large beam weapons will ignore it. One of the biggest advantages of the shield is its ability to pass through solid objects. By pressing against walls or floors, the player can "push" the shield through them. Any enemy that the shield touches will be damaged by it continuously. Like the gun, it can help a player attack an enemy without exposing them to damage.
After completing the game, the player is congratulated, but informed that the robot did not survive the alien station's explosion. The player is then given a password which, when entered, restarts the game on expert difficulty. After completing the expert mode, the player will be congratulated again and informed that this time the robot was able to successfully escape the destruction of the alien planet.
The game has 6 normal stages and 1 boss rush stage.
- Stage 1: The basic stage, which gradually introduces the player to the gravity flipping mechanic.
- Stage 2: This is the first stage to allow scrolling through the top and bottom of the screen as the player falls: instantly reappearing on one side after disappearing off of the other.
- Stage 3: This level is focused on a track on which an infinite number of enemies spawn.
- Stage 4: The entire level takes place inside of a small box, which moves without input from the player.
- Stage 5: This level is a race against the clock, as the player attempts to stay ahead of an oncoming electrified wall.
- Stage 6: This level focuses on gravity based puzzles, as all objects in the level are continually scrolling between the top and bottom of the screen.
- Stage 7: The final level, this stage is essentially a boss rush, culminating in the final boss fight, and the end of the game.
At the end of every stage the screen will go dark, followed by the flashing red text, "RED ALERT," indicating the beginning of a boss fight.
- Stage 1: This boss is a giant machine attached top of the screen. This boss attacks the player with lasers as well as an unnamed purple projectile.
- Stage 2: This boss consists of a series of turrets set in the far right wall.
- Stage 3: This boss is a turret that moves between four quadrants of the room, each of which is separated by lasers. The section of the room that the boss moves to is determined by which quadrant the player was in when the boss began to move.
- Stage 4: This is actually 3 separate entities; a red orb that bounces around the space the player is confined in, damaging the player if it makes contact with him, and two other enemies beyond the reach of the player, which fire lasers vertically through the player's enclosed area.
- Stage 5: This boss has three different forms, each denoted by what color the boss is.
- Blue- Shoots diagonal lasers that bounce off of walls.
- Red- Shoots lasers that alternate curving up and down to target the player.
- Green - Shoots laser barriers.
- Stage 6: This fight focuses on multiple enemies, which the player must defeat without touching the walls, celling or floor, as each surface is electrified. During this boss fight the ship from Stage 3 of R-Type can be seen in the background, a homage to one of Irem's shooters.
- Stage 7: This fight is against three 3 stationary aliens. Killing one will bring a giant plug closer to left side of the screen. When all three are dead the boss fight is over.
The 1992 Famicom version of Metal Storm is moderately different from the NES version. Major differences include:
- The Japanese version features an opening cutscene before the title screen with credits in English and storyline in Japanese.
- Stage 6 of the Japanese version is significantly harder, as the top and bottom of the screen are electrified. This prevents the player from wrapping around from top to bottom (or vice versa) without taking damage.
- The Japanese version also features extra narration during the very last battle at the end of stage 7.