[3pts] Implement GameEventSystem using Observer pattern

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Description

Implement an event system using the Observer pattern for game-wide notifications.

IGameEventListener Interface

• OnEvent(GameEvent gameEvent)

GameEvent Abstract Base Class

• EventType (enum)
• Message (string)
• Timestamp (DateTime)

EventType Enum

• PlayerLevelUp
• EnemyDefeated
• ItemPickedUp
• PlayerDeath

Concrete Event Classes

• PlayerLevelUpEvent (includes new level)
• EnemyDefeatedEvent (includes enemy name, XP, gold)
• ItemPickedUpEvent (includes item name)
• PlayerDeathEvent (includes cause of death)

GameEventSystem Static Class

• Subscribe(IGameEventListener listener)
• Unsubscribe(IGameEventListener listener)
• Publish(GameEvent gameEvent)

Demo Implementation

• GameLogger class implements IGameEventListener
• Prints events to console with formatting

Requirements

• Include code comment explaining Observer pattern choice
• Thread-safe implementation (not required if single-threaded)

Acceptance Criteria

• IGameEventListener interface defined
• GameEvent abstract base class created
• EventType enum defined
• PlayerLevelUpEvent implemented
• EnemyDefeatedEvent implemented
• ItemPickedUpEvent implemented
• PlayerDeathEvent implemented
• GameEventSystem static class with Subscribe/Unsubscribe/Publish
• GameLogger demo listener implemented
• Code comment explaining Observer pattern choice
• All classes documented with XML comments