}} alt="The mage attacking enemies in the dungeon">
}} alt="">
## Hiro systems in action
All of the Hiro metagame data is defined in server-side JSON files. Read more about Hiro's [Configuration over code](../../../hiro/concepts/introduction/thinking-in-hiro/#configuration-over-code) design.
### Economy
The [Economy](/docs/hiro/concepts/economy/) system handles virtual currencies (i.e., gold), the shop, and reward mechanics. Players start with some gold and buy equipment through the in-game shop.
When a player purchases an item, the economy system handles currency deduction, validation, and inventory updating in a single call:
{{< code type="client" hideable="false" filename="ShopScreenView.cs">}}
```csharp
public async void PurchaseItemAsync(IEconomyListStoreItem shopItem)
{
try
{
await _economySystem.PurchaseStoreItemAsync(shopItem.Id);
}
catch (ApiResponseException)
{
// e.g., out of currency.
}
}
```
{{< /code >}}
### Inventory
The [Inventory](/docs/hiro/concepts/inventory/) system manages collectible and equippable items. In _Mage Mayhem_, that means hats and swords for your battlemage to equip.
Players toggle equipment by setting the "equipped" property to 0 or 1. When equipping a new item, any existing item in the same slot is unequipped first, and the whole change is sent as a single batch update:
{{< code type="client" hideable="false" filename="InventoryScreenView.cs">}}
```csharp
public async void EquipItemAsync(IInventoryItem inventoryItem)
{
// ...
if (IsItemEquipped(inventoryItem))
{
// Unequip: set "equipped" to 0
inventoryUpdate.NumericProperties[MageMayhemConsts.EquippedPropertyKey] = 0;
await _inventorySystem.UpdateItemsAsync(updateRequest);
return;
}
// Unequip any existing item in the same slot, then equip the new one
inventoryUpdateEquip.NumericProperties[MageMayhemConsts.EquippedPropertyKey] = 1;
await _inventorySystem.UpdateItemsAsync(updateRequest);
}
```
{{< /code >}}
### Achievements
The [Achievements](/docs/hiro/concepts/achievements/) system rewards players for completing quests or tasks. In _Mage Mayhem_, quests track ranged kills, melee kills, and dungeon completions, awarding gold when milestones are hit.
After an arena ends, results are batch-submitted to multiple achievement IDs at once (the IDs are defined in the server configuration files):
{{< code type="client" hideable="false" filename="EnemySpawner.cs">}}
```csharp
private async void SubmitEnemyKillsAsync()
{
var achievementsSystem = this.GetSystem