Invaders -- FROM SPACE!

I am presently enrolled in an embedded systems class. Over the last three weeks, my lab partner and I had the opportunity to (dear readers: keep reading) implement Space Invaders on a Digilent Atlys board. It was fun.

I think my favorite part was the lab writeup where we had to describe the game in detail; upon encouragement from the denizen of a treeless plain in Africa, I have decided to post it here verbatim for your amusement. See, I don't like dry technical writing. It puts me to sleep. I also don't like arbitrary requirements. :D

Space Invaders for the Digilent Atlys

By:

[my lab partner and I]

Game History

Space Invaders was born in Japan in 1978 to one Mr. Tomohiro Nishikado. While he started as mere conceptual sketching, the game grew from there to become a unique prototype employing the latest microprocessors available, the Intel 8080, alongside helper chips and analog signal-shaping circuitry. This embodiment was then cloned by Taito to become the cabinet-style arcade game that produced a brief shortage of 100-yen coins in Japan.

Over its lifetime, the original Space Invaders out-grossed and out-profited Star Wars: A New Hope, placing it next to “The Greats” of entertainment in fiscal viability. This heralded the Golden Age of Arcade Games, when video games became part of popular culture. As per Wikipedia's description, many young people were inspired to explore the possibilities computers offered. The movie Tron—to which many older programmers owe their initial inspiration—was strongly influenced by this era.

Space Invaders offered one more revolution: oncoming hordes of destructible foes bent on the protagonist's destruction. From cheesy Tandy 8088 bartending games to Starcraft Zerg rushes to Halo’s Flood to AI War: Fleet Command, the allure of fending off uncountable enemies is felt in nearly every genre of video games since. Video Games Live, the traveling music event, uses it as their foundational memebase.

Game Play

The game is simple. The player directs a tank horizontally across the bottom of the screen while simultaneously shooting advancing aliens with the tank's slow-fire Laser Gatling Cannon and dodging said extraterrestrials' deleterious projectiles. Complete defensive bunkers have been installed prior to the beginning of the conflict; however, both player and alien projectiles will ablate them irrevocably upon impact.

Game Details and Specifications

The Tank

Player tanks can move across the bottom of the screen between the planetoid's surface and the defensive bunkers. Sadly, budgets are tight around here and hydraulics were too expensive, so the tank can only move along the surface. Superturbochargers are ineffective in vacuum, so tank speed is severely limited; however, inertial dampeners were pre-installed on this model so rapidly changing tank velocity involves no timing constraints. Tank motion is limited when the tank reaches either edge of its defensive zone, namely, the screen.

Due to the operational difficulties caused by relativistic battlefields, tanks can only have one laser pulse in flight at any given time. Once again, budgetary constraints prevented the use of plasma-steering or quantum-nihilation encoding, so bullets are fully absorbed by the first object they impact, whether alien, bunker, or outer space. 300,000 km/s is the upper limit for laser flight speeds, so one can only occasionally get a pulse between two full columns of aliens without impacting one. The top row of aliens will most definitely have moved by the time the pulse arrives; however, the bottom row is easily picked off without careful timing.

The player begins with three spare tanks prepared for immediate deployment under the leftmost bunker upon destruction of the current vehicle.

Bunkers

High-tensile-strength elastomer bunkers are provided that can withstand several weapons discharges. Each of the ten sections can take four impacts before they are ablated into oblivion. Note that the fast-moving alien projectiles can sometimes phase through the first layer and ablate the tile behind the foremost section.

Aliens

The player is pitted against five rows of eleven aliens of three types. Due to the varying ranges at which the aliens approach the player, more distance implies a higher point value. The creatures maintain a strict grid formation while they move. Defensive zones are divided such that the alien horde will move across the screen nearly to the edge, descend, and start moving towards the other edge. Should an entire column on one edge of the fleet be destroyed, the aliens will not descend until their still-extant forces reach the edge of the zone.

Enemy fire is distributed randomly across the fleet. Note, though, that only the bottom-most alien in each column will fire and that armada resources seem to be only sufficient for maintaining four projectiles in simultaneous flight. Each creature seems to mount two separate cannons: one which fires a fast-moving lightning projectile and another that drops a slower, mace-like particle blob.

Should you notice strange changes in the aliens’ shapes, please:

The aliens are not true shapeshifters; at the distances involved in this confrontation their mode of locomotion causes them to appear to shift between two guises, colloquially known as “out” and “in.”

Flying Saucers

Occasionally, mysterious craft are seen flitting behind the invading hordes. These are presently designated as enemy logistical support craft, so their destruction is handsomely rewarded. Speeds observed are usually three times that of alien lateral motion.

Victory and Defeat

The player's tanks are not equipped for close-range combat, so upon reaching the moon's surface the aliens receive the player's unconditional surrender. Damage caused to alien forces is tallied in the upper-lefthand corner of the screen as a “Score,” quite separate from the game's basso ostinato score.

Should the player succeed in destroying the alien armada prior to this unfortunate scenario, victory is declared and the player may rest assured of a life of privilege and ease, basking in recognition of his mankind-saving defensive prowess. Further alien invasions are possible but are not implemented in this universe.

Notes for This Blog Post:

History is summarized from Wikipedia's Space Invaders entry with minimal further research and some personal experience mixed in. Requirements are inferred from the behavior of the flash app provided kindly by Free Space Invaders (warning: email request and obscure link hunt required).