Contra/Versions

Arcade
The game was originally developed for the Arcade in 1987.

In this version, the snow field in Stage 5 was combined into one continuous stretch to the end of the game. It also is more difficult if the player is either doing well or farming enemies for points.

NES
The NES port was released in 1988 by Konami. It included the "Konami code", which allowed the player to start the game with 30 lives, and also allowed a few continues if the player ran out of lives.

The NES version has a non-lethal bridge at the beginning of the level, and makes the corridor run easier by removing the left/right turns and the timer.

Amstrad CPC
Ported by Ocean, in 1987. This version of the game has a few differences from the arcade version.


 * There is no scrolling. When you approach the edge of the screen (approximately 1/3rd screen-size away from the edge), the camera instantly moves to the next position.
 * The first corridor timer is 90 seconds, and the second is 2 minutes.
 * The boss fights at the end of the corridor run were split into separate stages.
 * The barrier causes the character to blink, and is also shown as a timer in place of the score.
 * The waterfall boss is visible even before you reach the top. It has the appearance of a normal base, with two side turrets, and a central 3-way turret. You can also defeat the boss while still protected by the barrier you collected at the beginning of the stage.
 * The second terminal boss has its two targets split in two as normal, but they more quickly return to their original position. They can also be one-shot killed by the laser.
 * Snow Fields is skipped. The later stages are combined into one continuous run, and do not contain the tank or giant.

Commodore 64
The Commodore 64 was ported by Ocean, under the name Gryzor. It is based on the arcade version of the game, but is more difficult due to implementation.


 * Weapons are slow-firing, even with the rapid fire powerup. However, you move faster compared to the NES version.
 * Stage 1 requires you to advance directly to the door before it becomes vulnerable.
 * As with the arcade version, you had to complete the corridor section within a limited time. Unlike the arcade version and other ports, the time allowed is much lower: you only have 40 seconds for the first corridor, and 55 seconds for the second.  Rolling floor grenades were omitted.
 * The boss fights at the end of the corridor run were split into separate stages.
 * The waterfall stage is shortened in one of the two Commodore 64 ports, and the boss is replaced by a simple base. It has two side turrets, and a central turret that shoots 5 bullets in a spread pattern.
 * The second terminal boss has one small soldier at the top, running along. It makes one shot before jumping down; to avoid the jump, avoid standing under the side
 * The final stage starts with the Snow field, and is a continuous run. However, it is shortened significantly.
 * The tank appears once, and the giant appears twice. If you have the barrier, you can run past the mouth without killing it.
 * The spike claws in Hangar are replaces by electric barriers that turn on and off.
 * The final boss is only protected by mouths, and doesn't launch spiders. The projectiles from the mouths bounce off the floor and ceiling.