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USE CASES

Play Game

Primary Actor: Player

• Description: To start the game double click on the provided executable. The player’s objective is to get from the start to the end of each level without exploding. The player can explode after getting hit 5 times with enemy missiles or by running into an obstacle or terrain. The player has five lives to attempt to pass the game.

Interface

Actor: keyboard

Primary Actor: Player

• Description: The game is a 3-d world in which the player maneuvers his ship up, down, left and right. To control the ship, the player uses the letter keys for "a", "s", "d" and "w". The "w" and "s" keys move the ship up and down. "a" moves the ship to the left and "d" to the right. When no arrow keys are pressed, the ship has no velocity. As soon as a key is pressed, the velocity increases and then stabalizes. The space bar is used to fire the ships weapon at the enemies.

Score

Actors: Enemies, Terrain

Primary Actor: Player

• Description: The game includes a score and a health meter. The player acquires points for destroying each enemy and for progressing through the levels. The point worth of various enemies is dependent on their difficulty level. The player’s health starts out at 100% and decreases each time he gets hit by an enemy missile. If the player hits terrain or an obstacle he dies immediately. The player has 5 attempts (lives) to pass the game. A life is lost each time the player’s health goes from 100% to 0%, and the player starts from the beginning of the level he is in. When the player has no more lives the game is over.

Colliding

Actors: Ship, Enemies, Terrain and bullets

Primary Actor: Player

• Description: The ship, enemies, terrain and bullets are able to collide in 6 different ways. When the ship (the player) collides with an enemy, the ship loses a certain number of health points and the enemy is destroyed. When the ship collides with the terrain, the ship loses health points and nothing happens to the terrain. Finally when the ship collides with enemy bullets (it will be unable to collide with it's own bullets), the ship will lose an appropriate number of health points and the bullet will be destroyed. When enemies collide with the terrain, they will lose all of their life points and will be destroyed. Nothing will happen to the terrain. When enemies collide with bullets that come from the ship the enemy will be destroyed as will the bullet. Enemies will not collide with their own bullets. Finally when bullets from either the ship or enemies collide with the terrian, nothing happens to the terrain and the bullets will be destroyed.

Kill Enemy

Actors: Enemy, Bullets

Primary Actor: Enemy

• Description: When a weapon fired by the user collides with an enemy, that enemy takes damage. If the enemy has taken enough damage, the enemy is killed (in an explosion, by falling, or by disappearing), and the player gains a fixed number of points.

Win Game

Actors: Player, Terrain

Primary Actor: Player

• Description: When the player reaches the end of a level (as defined by a particular distance from the start), the game is over, the player wins, and the player's score is displayed.