Planetary Defense Station

A patron pick that had the misfortune of going 0-6 in its time on the polls gets its due today. Poor old PDS, or Planetary Defense Station is one of those games that's so short that I wasn't sure how to cover it. It's a shoot-em-up set in outer space. Five levels. Very basic stuff. PDS is one of those games that not only is very short, but repetitive as well. An engine game with only a few levels and only minor differences between them.

Taken on its own, there's no article here. The playthrough video took all of six minutes from title screen to #endgame. Fortunately, when you look around beyond the ZZT file, PDS becomes much more interesting. Not only is this a rare instance of a ZZT world that later received a MegaZeux port (conversion even!), but it then got a proper remake where the game returned once more to ZZT, expanding on the original with significant changes to story, engine, and presentation. Both of the game's pseudo-sequels show a desire to improve upon the original, yet what "improves" a game varies quite a bit in each take on PDS.

Between classic, MegaZeux, and Enhanced, it's the third time that's the charm here, and I'm afraid you'll have to wait a bit before that one. For timeliness, and length concerns, I thought it would be better to do a two-parter. So right now, what you'll soon be seeing is a very slight ZZT game, followed by a look early ideas on what makes MegaZeux games "superior" to ZZT. Only later will I reveal and then finally figuring out how to hold players' attention when all you have is the simple moving and shooting gameplay of ZZT.

This is a series that's fill of missteps and glowups. An early title by a still very much learning ZZTer who went on to hop onto the MegaZeux bandwagon nearly as quickly as the program was released. There are baffling decisions that persist through all three games as well as unique bugs in every version. But getting to see the entire journey made me appreciate every step that much more. PDS is a doomed series by an author who just couldn't sit still long enough to make what they wanted to make before realizing how much better it could be if started anew, and that leads to a real sense of digging through the fossil record here.

Strap yourselves in. It's gonna be quite the dig.

PDS comes to us courtesy of Creator, a ZZT and MZXer of the mid-90s with a definite interest in space themed games. Perhaps her most recognized game among ZZTers was It's The End of The World!, a game which earned itself some recognition down the line via a Classic Game of the Month award in 2000, ensuring the game would never stray too far from the spotlight in the lineage of ZZT archives. It's an all timer that still holds up today, and was a game that I replayed again and again in my youth.

It even has a touch of space flair. A comet on a collision-course with Earth sees the player trying to inform the president of the impending doom, a journey with all kinds of unusual locations in a seemingly realistic world where you'll grab a bite to eat at a rest station, hang-glide your way to an evil king's castle, solve puzzles in a palace made of ice, and eventually flying up in a NASA built ship to destroy the comet and save humanity.

PDS doesn't have a whole lot in common, save for both games including a few solid depictions of spacecraft. PDS is early enough that it lacks any STK colors, leading to the station on the title screen being stuck with a pristine white chassis and quite bright solar panels attached to its body. Creator's way of mixing mundane and more surreal environments doesn't yet show in the first PDS. What you get is Space Invaders, ZZT-style, with only the briefest glimpse of a story to provide any more rationale than the un-abbreviated title already provides.

A quick blurb of story gets the game underway immediately. You play as an unnamed hero aboard Earth's Planetary Defense Station that hops into a ship to repel an invading alien force. Creator hints at something about the kind of person the player is through their initial disregarding of unexpected ships showing up on the radar. The only thing we get to know about the protagonist is that they almost doomed Earth by not taking the warning seriously. A glitch it ain't however, there are aliens on their way that are far more threatening than any number of red balloons might have been.

Before players even get an opportunity to check out their ship, Creator shows the controls which emphasize a baffling decision was in fact very much deliberate. Up and down steer the ship, but it's pressing left that causes your ship to fire to the right. Even in a literal three button game like this, I still sometimes found myself reflexively pressing right to fire in the direction my laser cannon (not canon) pointed, only to step away from the controls entirely and have to quickly race back into them. PDS is a newcomer's game, and one you should expect to not be as polished at it could have been. This is probably my biggest complaint about PDS.

It brings me no pleasure to inform you that it persists in both the MegaZeux game and much of the Enhanced release.

With the board no longer instructed, we get our first look at PDS. You get this long hallway with your ship at the very end. A few dollops of enemy ships are scattered around, and from there it's a matter of shooting down all the enemies with your cannon to open the door and proceed to the next level.

For this first level, the unnamed foes are content with keeping their distance and shooting towards you from where they start. Later stages up the difficulty a bit by having them slowly close in, mimicking the time limit of Space Invaders without replicating the invaders' strict marching formation.

The game doesn't actually end if an enemy ship makes it all the way across the board, however your ship will be unable to ever shoot it, creating an ever-present threat of soft-locking the game. It's still a game over, just one that the player needs to be the one to acknowledge. You are responsible for quitting, confirming, and restoring a save. The game makes no attempt to determine such a state is in play.

The enemy ships which are placed at different depths inevitably leads to the iconic friendly-fire situations any ZZT game that relies on objects to the do the shooting suffers from. Your role in the action is minimized by this, and it makes the invading force come off as inept. Recently in welcome to hell, we saw Tseng subvert inept objects in space dogfights by having wingmen

As for the engine itself, well, the one thing this game has going for it is just how early a game this is when it comes to ZZT shoot-em-ups. There are a few titles that definitely predate it, Jim Thies has a Space Invaders game from May of 94 and David Hetrick has the Enemies series. A few unknown dated games may also predate this one, but the titles that are more fondly remembered (namely Dogfight are still a ways off.

It's the first time somebody seems to have considered a horizontal layout over a vertical one at least. With ZZT boards easily being more than twice as wide as they are tall, you could argue that this allows for more varied enemy layouts. I think the benefit of such a thing is overrated given the slow movement of everything. A bullet needing to travel 40 tiles to reach its intended target rather than 20 slows the pace of the game down if enemy numbers aren't increased to fill this extra space. That just leads to more enemies shooting each other, so it's not really something that can be taken advantage of.

And speaking of slowness, this engine doesn't adjust the speed of any of its components. Everything runs every third tick resulting in a noticeable delay at times when you touch an arrow to move and have to wait two ticks before the object arrow acknowledges that it was touched. This delay may then be extended as ZZT uses the stat index to stagger objects executing on slower cycles. "Stat index + tick % cycle" can make things ever slower to respond.

Wait patiently for your ship to shoot... wait a few seconds for you bullet to reach the enemy you aimed at... and by the time it's actually in range to strike an object, you're left having to hope that the enemy is still around! With your targets being significantly farther away, your offense feels very arbitrary. The positioning of your ship and the enemy's at the time you shoot an attack has minimal influence on your accuracy. The only real strategy for offense beyond mashing fire to destroy enemy bullets and increasing the chances of hitting something, is to prioritize enemies that happen to wander to the borders of the screen. Once they're against a wall, it's harder for them to push away from it compared to enemies in the center that can move in either direction. Regardless of where enemies are, it doesn't feel like there's any real skill in shooting them. With infinite ammo and no real cooldown between shots outside of the inherit input delay from running at cycle three, your offense is an exercise in controlled mashing.

For your ship's defense, PDS takes a very extreme stance. There is no defense. One shot, and your ship explodes. I have to admit, this does instill a sense of tension, more-so when I was recording and curious if I could get through the entire game on a single credit for all my adoring fans, but in most ZZT shooters, the use of some kind of health bar for your ship is appreciated and expected. PDS demands perfect execution in game with unresponsive controls. It's only due to the generous amount of time it takes enemy shots to reach the player that it generally works out regardless.

Oh, and defeated ships turn into red fakes which reads as blood to me. If it was intended to be an explosion, it could do with an object erasing the tiles.

Completing a level opens up a path to the next stage. You're stuck walking entirely across the board like an early ZZT cut-scene, except there's nothing to look at. It's kind of a mandatory break, and probably explains why I kept wanting to press right to shoot, because I had to hold right for 10 seconds after finishing each level.

Level two. It's green now.

The enemies are initially positioned nearly as far back as possible to give players the most time to shoot them now that they can actually advance. These enemies actually move even slower than the first level's, really making sure that the player has plenty of time to stop the approach. Friendly-fire incidents can still happen even though these ships should move forward in lock-step. If a ship tries to strafe and bumps into the edge (or another ship), it will stop executing later code and try again on its next tick, allowing the enemies to become spread out horizontally.

Level three. Blue.

As you've noticed by now. PDS doesn't give the player any accolades. There are no messages to announce you success, no explanation about who these ships belong to, and no hints at characterizing our human pilot. Everyone has a strict role as either an object that shoots east or an object that shoots west.

The enemies start a little closer to reduce your time, and speed up dramatically, to the default speed of cycle three. This makes them as fast as the player's own ship. That could be threatening if they spread out more, but the distance is still large enough that you have plenty of time to move from top to bottom as needed.

Level four, cyan, does in fact mix up the formula a bit.

The play area is now filled with a mess of ricochets. These cause your shots to bounce back at you, making the strategy of shooting in a sine-wave pattern too dangerous to attempt. Not to worry though, as the enemies in this level are also immune to bullets rendering your cannon useless.

Victory then also can't be reliant on the enemies shooting themselves. In fact, they also don't bother attacking. Bullets just don't vibe with level four.

So how do you win? Well, when these ships are blocked to the west, they crash and explode. This explosion doesn't leave red fakes, but rather fires off some debris to the north and south. It's possible for an exploding ship to cause another to crash if the bullet happens to block the ship at the right time which is kind of neat.

The enemies simply defeat themselves. The ricochets are placed densely enough that it's quite unlikely for one to randomly navigate the path and reach the end of the screen. In fact, if ship crashed into your cannon, they'd die and the player would be unscathed. Crashes into the wall though result in the shrapnel hitting the player and ending the game.

Their movement is a bit scuffed as well. These guys have the new ability to move randomly in any direction, so they can even go backwards. However, they also move with #GO SEEK. Seeking causes their movements to aim towards the actual player in the lower left, not your cannon. Inevitably they march south and west. Most of them won't even make it past the lower-rightmost ricochet.

On a whim, I tried setting the speed to max and letting the level play itself out without any input, and only once did one of them make it through and #endgame. Even so, the nature of this level often leads to the game soft-locking instead of the player winning by doing absolutely nothing.

This is due to how the game determines if you've completed a level. In each stage, defeating an enemy tells the door that blocks the exit to go to a label that then zaps itself. There are an equal number of labels as there are enemies, with the final label leading to code that opens the exit proper.

If two ships are destroyed quickly enough they'll both tell the door to jump to the same label before it gets a chance to zap it the first time. This leads to the final label becoming impossible to reach and the level coming to a stop! Whoops!

This can technically happen in any level. It's just very easy to do so here as the ships all crash into each other as they head southwest. Setting the door (and ships) to cycle one would reduce the window where this could happen, but not eliminate it.

The fix is quite simple, and employed by later games like Dogfight. Rather than have enemy ships tell the exit to mark a downed ship, just have it check if there are any cyan objects still on the board.

Level five is the game's finale, and creator aims for something that looks a bit more spectacular. A huge ship has to be destroyed, and it's armed with a few smaller "missiles" that move and shoot, though I put missile in quotes despite that being the object name since they never actually advance. Two blink walls provide a shield for the enemy ship which prevents bullets from striking the red square inside that surely is the ship's weak point.

It is the weak point, but not initially. A pair of blink walls pointing at one another creates an invisible barrier that catches any bullets that attempt to cross. This is a clever little trick! Each cycle the first wall turns on a beam, and the second immediately shuts it off. The bullets are erased with no blink wall rays ever visible to the player as they're turned off before the next time the screen is redrawn.

To disable the lasers, players need to aim for the red triangle on the opposite side of the ship. Luckily, some deflecting objects are positioned so your bullets can be re-aimed at their intended target. Afterwards the square is fair game.

It's not much of a finale. At least it says "Boom"? The ship doesn't blow up or even disappear. The level relies entirely on players being too focused on dodging bullets and the red square to notice the deflectors that allow you to hit the real first target. Once you do, a single shot ends the stage.

And that's PDS. Like I said. There's not a lot here.

Creator is well aware that this game isn't much, ending things with a little note describing the game being an older title that was returned to, and acknowledging its lack of difficulty, and non-existent plot. It's one of those ZZT games where by the time it was completed, the author had already advanced their skills enough to identify the game's flaws, hoping you'll believe them when they say it will be even better next game.

If the engine didn't soft-lock so readily, it would be fine I guess. Creator is right though, the lack of story makes it hard to invest your energy into the game. Even the good ZZT shooters of the 90s aren't actually all that more involved than this as far as their engines go. But a good ZZT game needs to spark the player's imagination so that they can fill in the gaps themselves when the gameplay can't hold up to games made outside of the ZZT engine.

Even the best Space Invaders engine in ZZT is going to pale to the real deal. Chunky movement, slow projectiles, and enemies that can never do anything smarter than shoot in the correct direction and hope they happen to hit something are ZZT's limitations getting in the way of creating a frantic arcade shooter. It's a bland soup in desperate need of some spice. Whether that spice comes in the form of an interesting story, memorable characters, a unique setting, or something else, it's a necessary component to create a ZZT game that stands on its own.

PDS doesn't need all that much adjustment to turn the perfectly bland shooting from the game's highlight to just one piece of a greater experience. Some bits of story could do a lot to make the game something easier to take seriously. Get players to care with a story of an incoming alien threat, a race to man the turrets, then a series of wave after wave of blasting down bizarre enemy ships of unknown origin, and- oh no! The mother ship! It's here! Shoot some missiles into the core! You're Earth's last hope!!!!

You know. Add some drama! It doesn't have to be high art. It just has to be fun to play pretend.

Fortunately, that's what Creator goes on to figure out.

The next game in the series, Planetary Defense Station SUPER for MegaZeux is not the game where that happens, but it is our next stop on this journey.