A Simpsons Hit & Run-inspired open-world sandbox, built solo. Missions, NPCs, dialogue, a minimap and a physics-based car all had to work together, so I built them to be modular.
NPCs start missions, change state during them, and everything must be cancellable, restartable and saveable.
Polymorphism, dependency injection and the strategy pattern kept every system as modular as possible.
The systems ended up modular enough that I still use them in new projects.
A save system sits underneath all of them, and the physics-based car controller plugs into the same world.
Everything has to cooperate. NPCs start missions and change states during them.
Cancellable and restartable. Any mission can be stopped or reset cleanly, and still work with the save system.
Modular parts. Polymorphism, dependency injection and the strategy pattern let each system be swapped or extended.
// Placeholder example: replace with your real snippet (10-20 lines max)
public interface IMission : ISaveable
{
void Begin();
void Cancel();
void Restart();
}
public class Mission : IMission
{
readonly IObjective objective; // strategy: swap the goal
public Mission(IObjective objective) => this.objective = objective;
}Why it matters: a mission is built from injected parts, so new mission types don't require changing the ones that already work.
NPC system. NPCs start missions and change state as they progress.
Minimap. One minimap shows both NPCs and missions.
Car controller. A physics-based controller for the stunt car, built to fit the same world.
Missions that NPCs start and change state during, and that can be cancelled and restarted
NPCs with states that interact with missions and dialogue
One minimap showing both NPCs and missions
NPCs explain the world through dialogue
Physics-based car controller for stunts across the island
Saving works with every other system, including restartable missions
When building a game, it's important to plan for saving functionality from the start. A good way of doing that I found is by having clear states in each system.
By making systems independent & reusable I'm now able to carry them over into new projects.
With dozens of systems working together having a good debugging system & unit testing saved me a lot of time.
