Game Concept Document
By
James Stewart

Table of Contents
High Concept. . . . 3
Game Play. . . . . 4
Environment . . . . 7
Planet Gallery . . . 9
Celestial Bodies . . 10
Controls . . . . . 13
Target Audience. . . 14
Marketability . . . 14
Hardware Requirements. 15

High Concept
In the science-fiction 2D game Orbital, the player assumes the role of the commander of the Arc, a massive celestial vessel. Using orbital gravity as its only means of acceleration, the Arc must slingshot itself from planet to planet, rescuing billions of colonists before the universe itself ceases to be.
Four thousand years in the future, humankind has insinuated itself among the stars. Legions of human beings, inhabiting uncountable galaxies, work to expand their civilization throughout all of existence.
But now that existence is about to end. After centuries of space-folding transportation, quantum engineering, and other dalliances with the building blocks of creation, humanity’s ever-expanding influence has begun to unravel the structure of reality itself. Vast cosmic strings—humanity’s mass transit for decades—have begun to contract around inhabited solar systems, collapsing them into nothing. This crisis has already cost humanity trillions of lives.
The survivors’ only hope is the Arc, a colonization vessel roughly the size of Earth’s moon. Because light-speed engines and other quantum propulsion systems have become unreliable, the Arc must rely on planetary gravity to traverse space, whipping around galaxies and nebulae in order to evacuate systems that have not yet been destroyed by the cosmic crisis. Time is short, and billions must be rescued and find refuge… somewhere else.
Evacuate the universe. It’s about to collapse.

Game Play
A single mechanic underlies the entire design of Orbital—a simulation of orbital gravity. The Arc orbits a planet, constantly building acceleration. The player chooses a moment to escape the orbit, and shoots through space on a tangent line determined by the vessel’s current angular momentum. In order to complete a level, the player must guide the Arc from planet to planet using this form of transportation.
The player has three major challenges: First, to visit all available planets within the time limit. Second, the Arc must avoid collisions with comets, nebulae and other dangerous bodies (see Environment, p. 7). Finally, the player must maintain control of the Arc as it accelerates to faster and faster speeds, bouncing around the galaxy like a pinball. There are no brakes, no retro-rockets, no way to slow down.
Not that there’s time to slow down—to complete a single level, the player must navigate the Arc to each planet in the system in order to evacuate all colonists. When the Arc makes one full rotation around the planet, the player is rewarded with a cheering sound and a display of the number of lives saved (2-3 billion for a small planet, up to 50 billion for the largest). If the player completes this mission before the time limit is up, he or she moves on to the next stage and the game automatically saves. If time runs out, or the Arc collides with a dangerous object, the cosmic string surrounding the galaxy contracts, crushing the Arc and all the planets into a dense microscopic ball.

Figure 1: Entering and leaving planetary orbit. Planet images taken from www.jpl.nasa.gov.

Fortunately, the Arc is equipped with two devices to aid in its mission: A force field to deflect comets and survive nebulae, and a relativity engine that allows brief glimpses of “Tangent Time.” During Tangent Time, psychedelic music and colors distort the player’s view of space, but time moves much more slowly, giving the player a short window in which to plan an escape trajectory outside of the game’s usual frenetic pace.
Both the force field and the Tangent Time device are powered by collective psychic energy. The number of colonists already aboard the Arc serves as a battery. If the player relies too much on the force field or Tangent Time, this psychic battery is depleted; more colonists must be rescued before these powers are available once again.

Progressive levels become more difficult in several ways: more planets, increased distance between planets, more collision objects and shorter time limits. Each level will be laid out by a random algorithm, allowing for many possible levels and enhancing replay. After completing 100 levels of increasing difficulty, the Arc’s mission will be complete, and the new home of humanity will be revealed to the player through a psychedelic cut scene in which the Arc travels to another dimension.
Each level begins with the name of the solar system depicted in the level, the total number of inhabitants that need rescuing, and a one- or two-sentence tip that describes game play or a short explanation of new features (the level that introduces comets will explain comets, the first level in which a black hole appears will be preceded by an explanation of black holes, etc.). A robotic voice, created using the Sam Speaks program for the Commodore 64, reads the names of the solar systems and possibly voices the play tip as well.

Figure 2: Programmer artist’s conception of the Arc, the vessel the player will navigate through Orbital. Note that the Arc spins in the direction opposite the current direction of its orbit.

Environment
Each level of the game takes place within a single galaxy. Space is represented in a top-down 2D view. Planets and obstacles maintain static positions in the foremost layer, which the Arc and one or more comets bounce around. In the background, three layers of starry nothingness scroll in a parallax fashion, creating the illusion of a vast void.
Below is a diagram of a sample level of Orbital. For clarity, only the foremost layer is depicted. In this hypothetical level, the player must avoid the nebula in the center of the map and reach all planets before time expires. The Arc enters from the left edge of the level and begins circling the bottom-leftmost planet. The white line describes one possible course to all planets that also avoids the central nebula. Note that the Arc cannot reverse the direction of its orbit when it circles a planet.

Figure 3: A possible course through an early level of Orbital. The white line describes one possible path to all planets that avoids the central nebula. Celestial images are public domain and can be found at www.jpl.nasa.gov.

NASA’s Jet Propulsion Laboratory has made available a number of public domain images that can be used without copyright concerns. Several thousand photographs of planets, nebulae, comets and other celestial bodies are available through the www.jpl.nasa.gov website, giving the Orbital team plenty of visuals to pick from. The demo version of the game will contain 50 or so different planets, and a dozen or so nebulae, comets, black holes, etc.
The game screen itself will be as uncluttered as possible to allow for the largest possible view of “the majesty of space.” At the top center of the screen, a small map will show the entire layout of the level, much like in the arcade classic Defender. The player’s current score will be displayed in the bottom left hand corner.
The next page features a collection of planets already being prepared for use in Orbital.

Planet Gallery

Figure 4: Planet images are public domain and can be found at www.jpl.nasa.gov.

Celestial Bodies

There are no “enemies” as such in Orbital. The only real enemies are acceleration, the clock and dangerous celestial bodies such as comets and nebulae. That said, a few planets have beneficial effects. Dangerous and beneficial bodies are listed below:
Blue Planets
Blue planets will reduce the Arc’s speed by 10% after the vessel makes one complete orbit around the planet.
Green Planets
Green planets teem with life, allowing a small recharge to the psychic battery that powers the Arc’s force field and Tangent Time engine.
Ringed Planets
Ringed planets cause a temporary state of indestructibility for the Arc, and also forces it to reach maximum acceleration. The musical score will change to a particularly frenetic melody as the Arc bounces around the level at ludicrous speed, bypassing any black holes, comets or nebulae it encounters for the next 15 seconds.

Figures 5-7 (below): pictures of planets are public domain; available at www.jpl.nasa.gov.

Gold Planets
For 15 seconds, the tangent line from the Arc’s current position will display, much like the “cheat mode” in some pool hall simulations that show the path all balls on the table will take if a certain shot is executed. These lines will display in the main screen as well as on the map, allowing the player to see with certainty the available paths to other planets.
Comets
Comets bounce around the levels and slowly increase their acceleration, though not as much as the Arc does. If the Arc collides with a comet, the level is over and the player must restart. But if the player activates his or her shields before impact, the comet explodes with a pleasing ka-boom and a blinding flash of white light that fills the screen.
Nebulae
If the Arc flies through one of these gaseous giants, the vessel is destroyed. If the player activates the force field before crossing the body, a sizzling sound plays but the Arc will survive. Nebulae do not exert gravitational pull on the Arc.

Figures 8-10 (above): pictures of planets are public domain; available at www.jpl.nasa.gov.

Black Holes
Black holes exert their own gravity and cannot be bypassed by using the force field. Black holes present a dangerous opportunity to the player: They might be useful for changing course, but if the Arc gets too close, it is sucked inside and the level ends.
Cosmic Strings
Because of the fast pace of the game, it’s likely that the player will miscalculate the moment of release and send the Arc hurtling off into space. To avoid this possibility, each level will be surrounded by a glowing white cosmic string that undulates as if it is floating in water. If the Arc collides with the string, the string distorts then returns to its original shape, sending the Arc hurtling backward along its original path—and at much greater speed. If the time limit for the level runs out, this ring collapses, smashing all the planets together and grinding the Arc between them.

Figure 11: A galaxy with a black hole at the center. Image found at www.jpl.nasa.gov.

Figure 12: Shameful programmer art depicting a stylized cosmic string.

Controls
Orbital’s controls are very simple. Here’s the default layout for the keyboard:
Up Arrow: Accelerate—increases the rate of acceleration while in orbit.
Down Arrow: Slow Acceleration—the Arc still accelerates, though at a slower pace.
Ctrl: Activate Shields—destroys comets and allows the Arc to bypass nebulae.
Alt: Escape Orbit—while orbiting a planet, this button causes the Arc to fly off into space.
Space Bar: Activate Tangent Time—instigates a bad trip of waving colors, strange music and slows the clock, allowing the player more time to decide on an escape vector, activate the force field, etc.
Escape: Brings up the menu, allowing the player to start a new game, view high scores, or exit.
Orbital also features DirectPlay support for any 2+ button game pad.

Target Audience
Orbital is designed to appeal primarily to younger, casual gamers—it is a fast-paced game with cosmic visuals and a pleasing kinetic. The simple control scheme and arcade-style play make the game easy to learn. Because the first levels are not too difficult to master, players will be able to get a sense of the game before it becomes too challenging. Since the player’s game is saved after every board, the frustration factor is kept to a minimum.
Orbital will also offer three difficulty settings, allowing the player to set the level of challenge. At higher difficulties, the rate of the Arc’s acceleration is increased, and the time limit to complete each level is reduced.
Marketability
Orbital is envisaged as a free game that could be available through sites (such as Yahoo! Games) that rely on advertising to turn a profit. Because of its simple design, this game is also portable to a Java Applet format.
Orbital might work as part of a bundle of arcade-style games, or as inexpensive shareware.
Though the initial version of Orbital will be a demo, it will have 100 playable levels generated by a random algorithm. The demo will be a fully playable game.

Hardware Requirements
Orbital is designed for a Windows XP system with a 2 GHz processor and 1 gigabyte of RAM memory, with at least 200 megabytes of hard-drive space available. The video card must support a resolution of 1024 x 768 in 32-bit color. Sound card is optional but recommended. DirectX is not required, except for game pad support.
In practice, Orbital will run with much lower system requirements. A more realistic set of requirements might be: Windows 98 or later, Pentium III 500+ MHz, 64 megabytes of RAM, 30 megabytes of hard-drive space.

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