009-movement-system.md

009 - Movement System

Context

In D&D 5e, creatures have a speed (e.g., 30ft) and can move up to that distance during their turn. We need to track how much movement a creature has used or has remaining to enforce this limit.

Decision

We decided to encapsulate movement logic in an IMovement interface composed into ICreature.

Key Components

• IMovement: Tracks Speed (base) and MovementRemaining (current turn).
• StandardMovement: Concrete implementation.
  • Move(int distance): Reduces MovementRemaining. Throws if distance > remaining.
  • ResetTurn(): Resets MovementRemaining to the current Speed.
• Integration:
  • ICreature exposes a Movement property.
  • StandardCreature.StartTurn() calls Movement.ResetTurn().

Consequences

• Pros:
  • Enforcement: Prevents illegal movement distances.
  • Automation: Resets automatically at start of turn.
  • Flexibility: Speed property on IMovement delegates to ICombatStats, so changes to stats (buffs) are immediately reflected in the next reset.
• Cons:
  • Grid Independence: Currently just tracks abstract "feet". Grid-based logic (diagonals, difficult terrain) would need to be handled by a higher-level system (e.g., a Map Manager) that calculates the "cost" of a move and then calls Move(cost).

Status

Accepted and Implemented.