Use Case 4--Set Level

Context of Use:
User interface from where to specify the starting level and difficulty of the game. Difficulty is adjusted by modifying the ghost (enemy) speed.
　

Scope:
J2ME Pac-man Game Application
　

Level:
User Goal
　

Primary Actor:
Mobile Phone or PDA User
　

Stakeholders and Interests:
The user who wishes to change the starting level and difficulty of the game.
　

Precondition:
The J2ME program is already running.
　

Minimal Guarantees:
Preference variables "StartingLevel" and "GhostSpeed" are set to valid values.
　

Success Guarantees:
Preference variables "StartingLevel" and "GhostSpeed" are set to valid values requested by the user.
　

Trigger:
User chooses "Set Level" from the main menu.
　

Main Success Scenario:
　

• 1. StartingLevel read from Preferences
  　
• 2. GhostSpeed read from Preferences
  　
• 3. Screen is displayed with Ul interface to specify StartingLevel and GhostSpeed. The interface also contains a button entitled "Return to Main Menu".
  　
• 4. Wait for User Input {loop}
  　

Extensions:
　

• 1a. StartingLevel is out of range, or null.
  　
  • 1a1. The variable is reset to 1 (start play at the first level).
    　
• 2a. GhostSpeed is out of range, or null.
  　
  • 2a1. The variable is reset to 5 (a "medium" level of play).
• 4a. User adjusts StartingLevel Ul component.
  　
  • 4a1. StartingLevel preference variable is adjusted accordingly.
    　
• 4b. User adjusts GhostSpeed Ul component.
  　
  • 4b1. GhostSpeed preference variable is adjusted accordingly.
    　
• 4c. User selects button "Return to Main Menu"
  　
  • 4c1. Close current display and activate the main menu.
    　

Technology and Data Variations List:
None
　

Related Information:
PacMan Use Case 4 Collaboration Diagram
PacMan Use Case 3 and 4 Class Diagram
PacMan Package Diagram
Pac Man Use Case Model