C++ Framework

The core Unreal Framework layer establishes the game session lifecycle, business day logic, player wallet, and input routing. AStarbudGameState hosts four manager components that own major gameplay subsystems, keeping them server-authoritative and replicated from a single authority actor.

The business day system drives all customer and shop activity. A day is started from the in-game ShopTerminal; customers only spawn when a business day is active and only purchase listed items.

The interaction system uses a lean interface + component pattern. Any actor can become interactable by implementing IInteractable and attaching an UInteractTargetComponent. The player's UInteractionManagerComponent performs a sphere trace each tick to find the nearest valid target and drives the interaction prompt UI.

A replicated slot-based inventory that can be attached to any actor. Items are identified by UItemDefinition data assets — no hard-coded item types. Category filters allow specific storage actors or machine slots to restrict accepted item types without touching code.

A screen-stack UI manager keeps input mode and widget lifecycle fully controlled from C++. Each screen is a C++ class with Blueprint child classes for layout and visuals. The subsystem enforces that only one screen is active at a time and handles the transition from Game-only to UI-and-Game input mode automatically.

Nine dedicated screens cover all major player interactions:

The player character wires together camera, interaction, and inventory into a single controllable pawn. All input actions use Enhanced Input. The character delegates interaction logic to UInteractionManagerComponent and inventory operations to its UInventoryComponent, keeping the character class thin.

The grow system manages plant lifecycle from seed to harvest. Plants are defined by UPlantDefinition data assets which encode growth time, yield, and trait profiles. The grow component uses FTimerManager for tick-free progression and supports save/load restoration via ApplyFromSave.

Strain genetics integrate directly here — each FPlantInstance carries a strain ID referencing the strain registry. At harvest, actual yield and quality are calculated from the strain's trait profile multiplied by grow health.

The shop system handles product listings, active business day management, reputation tracking, and revenue reporting. Listings are set up via the ShopTerminal; customers reference active listings when deciding what to purchase. The shop counter provides a quick-access restock interface and shows live sale notifications during a business day.

Customers are AI-driven NPCs that enter the shop during a business day, browse active listings, make a purchase, and leave. Each customer type is defined by a data asset encoding trait preferences, budget range, patience, and visit behavior. The customer manager spawns and despawns customers according to the business day schedule.

Traders are buy/sell NPCs. They come in two forms: preplaced marketplace or blackmarket stalls configured in the editor, and dynamic car traders that arrive via the event system for a limited time. Both use the same UTraderComponent for all trading logic — the only difference is how they enter the world and their editor-configured availability windows.

Storage actors provide passive item storage in the world. Each storage unit carries its own inventory component with configurable category filters, allowing specific units to be designated for seeds, harvested product, materials, or any mix. A lock flag prevents unauthorized access in co-op.

The building system implements a directed acyclic graph (DAG) tech tree for shop upgrades. Each upgrade is a data asset that encodes prerequisites, currency cost, gameplay effects via GameplayTags, and optionally an actor to spawn in the world when purchased. The BuildingManager handles wallet checks, prerequisite validation, and state restoration on load.

Machines are interactable actors that process items over time according to recipes. A machine has input slots, output slots, and a processing cycle driven by FTimerManager (not per-tick). Recipe data assets define which items are consumed, what is produced, and how long each cycle takes. This system covers processing equipment, the breeding station, and any future automation machinery.

The save system is a UGameInstanceSubsystem that orchestrates a full gather-and-apply save flow. On save, it queries all registered saveable systems and aggregates their state into a single UStarbudSaveGame object. On load, it distributes the saved data back to each system's ApplyFromSave function. Actor positions and placed objects use FSoftObjectPath in save data — never raw pointers.

The station system manages the multi-island world architecture. The game world uses a persistent level with station islands as streamable sub-levels. Each island is a self-contained ASpaceStation that contains one or more AStationRoom actors. Players can rent, purchase, or release stations; the starter station cannot be released.

Each station has a configurable purpose (Selling, Production, Storage, Mixed) which controls which gameplay systems activate on that island, and a condition tier (Derelict through Luxury) that governs the visual state via Blueprint material events.