The bridge model

The bridge is the typed contract between your Unity game and your Solid UI. You define it in C#, and Loom generates the matching TypeScript surface.

There are three concepts:

State

State is data the UI reads:

public int Health { get; set; } = 100;

When C# assigns a new value, the UI updates:

const bridge = useBridge();

<span>{bridge.health}</span>

Use state for values that have a current truth: selected screen, player health, inventory snapshots, loading progress, current scene, and settings.

Actions

Actions are public C# methods tagged [BridgeAction] that the UI can call:

[BridgeAction]
public void OpenInventory()
{
    CurrentScreen = GameScreen.Inventory;
}

The UI calls the generated action proxy:

await bridge.openInventory();

Use actions for user intent: click, confirm, purchase, equip, submit, start, cancel.

Events

Events are one-shot messages from C# to UI:

public Event<DamageEvent> TookDamage { get; } = new();

Use events for moments rather than durable state: damage flash, toast, reward burst, alert sound, or animation trigger.

Choosing the right primitive

• If the UI needs to know the latest value, use state.
• If the UI is asking the game to do something, use an action.
• If the game is announcing that something happened, use an event.

The next pages go deeper into each piece.