Difference between revisions of "Meteor Madness"

Revision as of 10:01, 12 January 2008

Display Name: Maritime Defender

File:Wormhole small.png File:Foe small.png File:Explosion small.png

Abstract

This mini-game resembles the arcade games Tempest and Asteroids, and combines tests of motion coherence threshold, motor inhibition, and executive flexibility. The player commands a spaceship that moves clockwise (left arrow key) or counterclockwise (right arrow key) around the perimeter of a circular field. Slow-moving meteors materialise at the centre of the field and drift outward; the player must fire torpedoes (space bar) to destroy these meteors. (This ongoing task serves simply to maintain vigilance.) Periodically, a wormhole materialises within the field. The player can open this wormhole by moving around the circle to align with it, then connecting with the wormhole (up arrow). Connecting temporarily drains the ship's propulsion systems; the ship is locked in place in front of the wormhole as an unidentified ship begins to emerge. This ship can be either a friend or a foe, with equal probability. Friend and foe ships are identical in area and luminance, but differ subtly in form: one has two warp nacelles protruding, the other three. Foes should be fired upon and destroyed before they get a chance to attack the player. Conversely, withholding fire on a friend is rewarded by a weapons power-up which increases the player's firing rate. (This change in firing rate alters the game tactically but does not affect measurement of reaction times.) Friends and foes cannot be discriminated until they have emerged from the wormhole. Thus during the opening of the wormhole the player must prepare, but not execute, a motor response. Foes do not fire, and friends do not deliver weapons power-ups, until 800 ms after emerging. A hit in this task is therefore defined as firing on a foe within this 800 ms interval, a miss as failing to fire on a foe within this interval, a correct rejection as withholding fire on a friend, and a false alarm as firing on a friend. This task behaviourally measures inhibitory function, and can be used in conjunction with EEG measures to assess motor planning.

Friendly and enemy forces in this game are pirates or mercenaries who have requested the player's help (to fend off the pirates). The class of ship used by each side therefore can change from one session of the game to the next. A shift session is one in which the assignment of ship classes differs from that of the session immediately preceding. A hold session is one in which the assignment of ship classes does not differ from that of a session immediately preceding. Differences in reaction time and accuracy for the fire-or-withhold task between shift and hold sessions measure executive flexibility.

After the player has completed a session of five wormhole connections, the ship warps to another meteor field. Whilst in warp, the player views a field of 200 stars (white dots on a black background), a percentage of which move coherently in one direction, either left or right. Other stars move in random directions. Each star appears in the field for four video frames, or until its motion carries it outside the boundary of the field. Coherent motion of the star field signals that the ship is veering right (for leftwards apparent motion) or left (for rightwards apparent motion) of its intended course. The player's task is to compensate for this drift by steering left (left arrow) when leftwards apparent motion is perceived, and right (right arrow) when rightwards apparent motion is perceived. Failure to compensate for an actual drift or compensation when no drift is present causes the ship to collide with this mysterious subspace matter, draining its shield and possibly resulting in its destruction. Each drift interval lasts 2 seconds plus a random and uniformly distributed interval between 0 and 250 ms, or until a course correction is commanded. The player's motion coherence threshold is estimated via parameter estimation by sequential testing (PEST). Since the threshold adjusts to the player, it is expected that about half of the trials will result in a failure. To avoid frustrating the player, approximately every 4 trials is a dummy trial with an artificially high coherence threshold.

Premise

A "nearby" freighter is under attack by marauders! Warp to its location and destroy all hostile forces before it's too late. Friendly escort ships will assist you with weapon upgrades.

Objective

Salvage as many survivors and goods as possible whilst keeping your own ship alive.

Characters

Cheetah C-24 Fighters: The colony's squadron of high-speed attack ships. They are equipped with magnetic photonic torpedoes. The Cheetah's shields are capable of absorbing substantial energy surges before becoming vulnerable to enemy fire or physical collision.

Wormhole: Requires 2 entities to open; one on each side. These appear during the shooter phase and with the help of the player allow a resource or a hostile to warp through to the player's location.

UFO1,2: Marauding space pirates or mercenaries (depending on the session). They are both equipped with weapons and capable of destroying C-24 Fighters.

Meteorites: Come in a couple of different shapes and sizes. Slamming into one causes a hit on a ship's shields or destruction if the ship's shields have failed.

Subspace Matter: Random particles that fly through space in a logical manner when piloting at regular speeds, however in warp drive they seem to defy the laws of physics.

Gameplay

There are 3 phases to this minigame. The game begins at level 1 in the shooter phase. After this, the ship uses a wormhole to enter a warp-jump phase that lasts for about 15 seconds. This cycle is repeated 4 times (unless the player dies). The final phase is a boss phase.

The player's shield persists through all phases. After taking a hit, the shield is reduced by 1/2. Thus, 2 hits are enough to deplete the shield, leaving the player only 1 more hit before dying in an exploserous ball of flame. Shields slowly recharge over time (about 10 seconds for a full charge, but this number will likely change upon play-testing), but once a shield is fully depleted it does not recharge leaving the ship permanently vulnerable to one more hit.

Warp-Jump Phase

This phase tests the subject's Motion Coherence. During warp-jumps, the mysterious dots move in a mostly random manner. A small percentage of these particles begin to drift in the same direction indicating that the ship is veering off course. The player must correct the ship's course by pressing the arrow key corresponding to that directional drift. Once the drift starts, the player has only a couple seconds to react. If no correction is made in time, the ship slams into debris and takes a hit. This phase ends after a set amount of time which is not disclosed to the player or the ship is destroyed.

The percentage of drifting stars is determined by PEST.

Dog Fight Phase

This phase tests the subject's focused spatial attention.

The playing field consists of an invisible cylinder whose caps are parallel to the camera's viewing plane. The player's ship is located at the near cap. All entities can only exist on the cylinder's circumference but may rotate around it or move up and down it lengthwise.

The player may fire, sending projectiles down the cylinder lengthwise. At first, the rate of fire is fairly slow, but as the player collects powerups from friendly ships that rate increases.

It may be necessary to add a wingman if many autistic players have trouble with this phase. The wingman would automatically move and fire upon enemies/meteors.

Wormholes appear at the far cylinder cap. The player can align his/her ship with a wormhole and activate it. A short time later, a ship (friendly or foe) replaces the wormhole. The player should immediately fire and attempt to destroy any hostiles. Should the player fire enough times upon a mercenary, it is destroyed. If a mercenary survives the trial, it awards the player with a weapon upgrade. Similarly, if a hostile is destroyed it leaves a small cash collectible behind.

Additionally, meteorites appear at the far cylinder cap and scroll down its circumference towards the camera. If they hit a ship, then the meteor is destroyed and the ship's shield takes a hit. Meteors will not appear in a column that is occupied by a wormhole. Meteors can be destroyed by shooting them.

Boss Phase

The final phase is a boss battle. This boss will not be incredibly difficult, but serves mostly to give the player a sense of accomplishment and reward them by letting them blast the away at a something with their upgraded lasers.

User Interface

For the warp phase, the only input will be left and right arrow keys to indicate a course correction. The HUD consists of a inner-cockpit view. The cockpit will remain static during test trials, but between trials will blink or sound to provide positive/negative feedback for successful/failed trials.

While in the shooter phase, pressing the left arrow key rotates the player's ship clockwise, while right rotates it counterclockwise. This would normally seem counterintuitive, but in this case the player's ship is displayed upright when it is near the bottom of the screen. Therefore, pressing left always shifts the C-24 to its port side. Spacebar fires weapons. Pressing the up arrow key will attempt to open a partial wormhole. This attempt is successful if the player is aligned with the wormhole (ie, they are near the same position on the opposite cylinder caps). A different color beam will indicate a successful or failed wormhole activation.

To minimize distraction, the shooter phase has no HUD. Shield power feedback is given through the color and opacity of the shield particle effect when a player gets hit.

The UI for the boss phase is identical to the shooter phase.

Scoring

Defeating the boss rewards a lump sum of cash. A colony structure is awarded if the player collects enough powerups. Any cash collected from destroyed enemies is also kept. Money is subtracted for the cost of each derelict ship destroyed by the player. If this dips the reward into negative money, then the money rewarded is set to 0.