Gorf: Unfixing the Shooter

Animation and gameplay of Gorf, showing some of the enemy and boss sprites.  Gameplay is taken from the first stage, a Space Invaders clone.


By early 1981, shooters were still the dominant genre in arcades.  The Galaxian model had spawned many imitators, but there were limits to how much variety could be achieved within the constraints of a fixed shooter.  

Indeed, one could reasonably ask: why was the shooter fixed to begin with?  Well before Space Invaders was released, there had been shooters that allowed players to navigate two-dimensional space.  Midway's Gun Fight, for example, had players moving around a two-dimensional playing field while firing at each other.  But from the release of Space Invaders until 1981, most shoot-em-up style descendants opted to fix the player's motion along one axis.

That all started to change, however, with games like Defender, Scramble, and Gorf.  I'll cover Defender and Scramble in more detail later, but of these games, the clearest window into the transition out of fixed shooters is Gorf

Gorf

Gorf is a Midway product, released in early 1981 and designed by Jamie Fenton.  It was originally intended to be a tie-in to Star Trek: The Motion Picture, but that idea was eventually abandoned and it was created as a standalone game.  At first glance, it resembles a standard fixed shooter, but some key differences will be apparent as soon as you start playing.

Key Mechanics

Take-Back Firing

A clip demonstrating the player firing system used in Gorf.  The player can fire rapidly, but only by replacing previously fired bullets.
For every bullet you fire with your ship, Gorf presents you with a choice.  You can let that bullet fly as far as it will or, at any time, take it back and fire a new bullet.  This makes for some interesting strategic possibilities from the player's standpoint.  Rapid take-back firing can be useful for taking out groups of nearby enemies, but if you're aiming for a distant enemy formation, you'll need to wait before firing again.  

2-Dimensional Motion

Even though Gorf has clear antecedents in fixed shooters like Space Invaders and Galaxian, sometimes going as far as to copy them sprite-for-sprite, it makes one simple mechanical change that makes all of the difference in the world: the player can move left/right and up/down.  This change feels very natural and straightforward from the player's standpoint -- after all, we're used to moving into empty space -- but a designer has to think hard about how this changes the gameplay.  Fenton clearly did, and in the following sections, I want to look more carefully at the impact of this change.  

Stages

Gorf breaks down into five different stages.  After you've finished all five stages, they repeat at a higher difficulty level, with up to six levels of difficulty.

Astro Battles

"Astro Battles" is essentially a Space Invaders clone, even going so far as to use the sprites from the original arcade game.  Of the five stages, it gives you the least freedom to move up and down.  This actually makes sense -- if you think about the original Space Invaders design, it's difficult to find much use for that extra degree of freedom.  If the player moves up on the screen, they get closer to the alien bullets and no longer can use the bunkers.

Two changes in Gorf give you some use for that extra movement.  First of all, the bunkers are replaced with a force field, which you can shoot through, so moving upwards a little still keeps you behind the protective shield.  Secondly, there is a brief period at the beginning of the stage in which you can shoot at the aliens without worrying about enemy fire.  During this period, you can move closer to the armada and take them out in rapid succession (see the animation at the top of the article for an example).

Laser Attack

A clip of gameplay from the second stage of Gorf, where the player faces off against aliens with laser beams.
The second stage, "Laser Battle", is not a direct clone of any previous arcade shooters, but it's clear the developers were familiar with the genre.  The coordinated movements of the enemy groups are similar to the flight patterns in Phoenix, where they jump in straight lines between screen locations and occasionally send divers at the player.  The dive patterns are not nearly as complex as in Phoenix, however, and more closely resemble those in Galaxian.  Finally, the laser attack may have been inspired by games like Space Beam, released two years prior, in which two ships armed with lasers face off against one another in an asteroid field.

The most significant effect of the laser attacks is to restrict the movement of the player.  Unlike with bullets, you can't go around a laser attack, so moving up doesn't do you much good until you've knocked out one of the lasers.  Even then, you'll usually want to focus on moving left-right -- the laser attacks come so quickly that you can easily be caught off guard moving vertically.  And by the time the lasers are both destroyed, it's pretty smooth sailing, with or without vertical motion.

Galaxians

A clip of gameplay from the third stage of Gorf, where the player takes on an armada of Galaxians.
"Galaxians" makes no attempt to hide its design origins, even going so far as to use the same sprites and dive patterns as the original Galaxian.  Fortunately, this provides an excellent testing ground for unfixing the shooter.  What would it be like to play Galaxian if you could move up and down?

The answer, as it turns out, is that it's still a lot of fun, but requires a lot more enemy activity in order to challenge the player.  With that extra degree of freedom, you can now weave around the enemy attacks and pick your approaches to the diving aliens.  Fenton clearly realized this, sending divers in frequently and raining down bullets in higher concentration than the original game.

Yet the overall flow is remarkably similar to the original, bringing into question whether the Galaxian model ever needed to be fixed, at least from the design standpoint.  There's still a question of the demands on the hardware, but I'll address that further down.

Space Warp

A clip of gameplay from the fourth stage of Gorf, where the play shoot aliens coming out of a vortex at the center of the screen.
The fourth stage is quite different from the previous three, with enemies only emerging one at a time from the center of the screen.  All enemies start as very small sprites and gradually spiral outwards at an increasing speed.  The spiral geometry is similar to what would eventually be used in tube shooters, like Tempest and Gyruss, but this isn't a proper tube shooter -- the player is still restricted to planar movement in Gorf.

With just one enemy appearing on the screen at a time, it's difficult to challenge the player without a fairly sophisticated AI.  What Fenton does instead is to keep the enemy very small for most of its flight, making it difficult to target, and then increasing its motion rapidly at the end.  Unfortunately, the result of this is that targeting is mostly a crapshoot.  I found myself just firing at the center of the vortex and hoping that my shots would make contact with the enemy in its flight.  In addition, enemy fire takes a straight path from the alien to the player, so you need to be constantly on the move in order to avoid getting hit.  You have plenty of freedom to move up and down, and you'll want to make use of that freedom when avoiding diagonal shots and outward-spiralling enemies.

While it's true that this particular design wouldn't have worked in a fixed shooter, I don't think it works that well in Gorf either, so I don't think it's a particularly useful reference point for unfixing the shooter.  It is interesting, however, how this tube-like geometry seemed to pop up so quickly at the same time that 1-D motion went out of vogue.  Perhaps this stage was also influenced by first-person space shooters of the late '70s, like Star Raiders and Star Fire, where enemies grow from perspective as they get closer.

Flag Ship

A clip of gameplay from the fifth stage of Gorf, where the player faces a boss starship behind a protective shield.
In the final stage, you face off against a large starship that resembles a torpedo with a tail.  In order to destroy it, you must break through its protective shield and then hit the core at the center.  There's one spot on the ship, at the intersection of the tail and the hull, where it's immediately vulnerable to destruction.  Failing that, you'll have to chip away at the hull until the core is revealed.

The most efficient way to destroy the protective shield around the ship is to move up close and chip into it with rapid fire.  Even at the higher levels, I found I was still able to do this while avoiding enemy fire for a short period.  After that, you can aim at the ship, but you'll want to consider backing up because the combination of enemy shots and falling shrapnel can be hard to avoid at close range.  Of course, moving back will be make it harder to hit the ship's vulnerable point, so you'll need to pick an optimal point for your playing style and ability.

Aside from the Galaxians stage, the boss battle makes the best use of the player's two-dimensional freedom and it anticipates the more mechanically complex boss battles that would become common in side-scrolling shooters, like Gradius and R-Type.

Why Fix a Shooter?

The fixed shooter is really more a product of its time than any kind of game design ideal.  Tomohiro Nishikado's design for Space Invaders was heavily influenced by ball-and-paddle games like Breakout, in which the player's movement was similarly fixed.  And left-right movement is all you really need in Space Invaders -- the layout of the bunkers and the slow-moving block formation make vertical movement extraneous.  

After that, given the overwhelming success of Space Invaders, I'm sure that many shoot 'em up designers were hesitant to stray too far from its basic mechanics.  I think most of the fixed shooters from 1979 - 1981 could have allowed the vertical motion without sacrificing in gameplay, but only if the hardware could have handled the load.  The hardware of that period was certainly capable of rendering two-dimensional player movement, but the question is whether it could have handled the amount of enemy activity necessary to challenge a player with full two-dimensional freedom.  It's hard to answer this in general, but I can say that in the case of Galaxian, the original hardware only allowed seven sprites at a time.  By contrast, in the "Galaxians" stage of Gorf, you will sometimes see more than eight or nine diving enemies, even at the lowest difficulty level.  

That being said, Galaga was also a fixed shooter, and it had much more sophisticated sprite hardware than Galaxian.  Given how elaborate the enemy movements are in Galaga, I feel sure that an unfixed version could have been made that provided sufficient challenge to the player.  And considering how much fun it is in its fixed form, maybe there's a third answer to the question of why you might fix a shooter.  Maybe, sometimes, it's just better to keep it simple. 

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