Gradius/Versions

Amstrad CPC
Developed by Cyclone Studios and published as Nemesis in Great Britain in 1987 by Konami.

Commodore 64
Programmed by Simon Pick ad published as Nemesis in Great Britain in 1987 by Konami. Released in the United States as Gradius.

MSX
Developed by Konami and published in 1986. The differences are as follows:
 * Scrolling (in many game, not just this one) is not smooth and stutters throughout the game, albeit at an even pace). It can take a couple of game plays to get used to it.
 * Most enemies are one solid color (another common characteristic of MSX games). Attack waves are not nearly as intense since the MSX can only display so many sprites at one time.  In exchange, some of the enemies are harder to kill.
 * Only a maximum of two Options are permitted, due to sprite limitations.
 * Missiles and Lasers have two levels of power. Selecting them once gives you the initial level, selecting them again gives you the second.  Missiles get faster, Lasers get longer (the first level of Lasers is less than half the length of the screen).
 * Shields remain one small size, and turn red when they can withstand one more hit.
 * The vertically scrolling stages (the second and third) do not scroll vertically anymore, and are fixed in their presentation.
 * There is a new stage, placed between the reverse volcano stage and the tentacle stage. It is bone themed, but different from the extra stage present in the PC-Engine version.
 * Four stages contain warps to secret bonus levels that provide points and extra lives. See the Secrets page for more information.
 * Another trick is present in the programming that allows you to play as TwinBee if the TwinBee cartridge is present in the second cartridge slot of the MSX.

NES
Developed by Konami and published in 1986. The differences are as follows:
 * Only a maximum of two Options are permitted, due to sprite limitations.
 * Lasers are reduced to a short beam the length of the Vic Viper. They are very quick, and still continue to fly through enemies.  Up to two may be fired on the screen at one time (that is, per ship and Options)
 * Shields remain one small size, and turn red when they can withstand one more hit.
 * All enemy characters are present, but simplified in palette. Some of the bigger enemies, such as the Big Core, have been reduced in size.
 * The vertically scrolling stages (the second and third) do not scroll vertically anymore, and are fixed in their presentation. (As a consequence, the Moai stage is much easier to go through along the top since you are only attacked by Moai from below.  However, you also have less space to maneuver in.)
 * The first four stages contain two points that provide bonuses. One will provide a 5000 point bonus, and the other provides an extra life.  (The sixth stage also provides an extra life, but no point bonus.)  See the Secrets page for more information.
 * The first three stages allow the player to activate a warp and skip ahead one stage at the conclusion of the fight with the Big Core if certain conditions are met. See the Secrets page for more information.
 * One of the first games to include the now-famous Konami Code. Using it provides you with a near-full assortment of power-ups, but may only be used once per game.

PC-Engine
Developed by Konami and published in 1991. A pixel-accurate conversion, considered by some to be one of the best ever made, topping the original. Others have disagreed. The differences are as follows:
 * To provide a separate space for the score and power-up bar, the vertical height of the display is clipped. The screen scrolls very slightly up and down with the player in order to see the full extent of the side he or she is closest to.
 * There is an entirely new stage (referred to in this guide as Stage X) that is exclusive to this version.
 * The sound track of the game has been remixed and given a substantial boost in quality. The drum tracks are more sophisticated in this version.
 * The follow motion of the Options is not as tight as the original arcade version, as it allows Options to cluster a little more tightly when small adjustments are made.
 * Some small changes were made to the weaponry. The laser is a lot longer than in the arcade, which can lead to collision detection issues.  The laser can be cut short (by releasing the fire button) and fired intermittently at different lengths, unlike the arcade.
 * The double-shot weapon was changed as well. You can fire more frequently with the double-shot activated than you could in the original.  For some reason, the laser sound is played when you fire the double-shot.
 * Some enemies have changed. The Ducker shoots more frequently.  The tentacles are very weak to laser attacks.  In the arcade, the Big Core used to warp from the top or bottom of the screen if it traveled to far in either direction.  It no longer does this.

Sharp X68000
Developed by Konami and released as a pack-in with the first version of this system. This conversion was considered so good, and that it demonstrated the strengths of the system so well, that it was included with the purchase of the system. It is a near flawless spot-on conversion with nothing taken away from (nor added to) the game play. The only area in which it suffers compared to the arcade is the music quality.

Sinclair ZX Spectrum
Developed by Cyclone Studios and published as Nemesis in Great Britain in 1987 by Konami.