> ## Documentation Index
> Fetch the complete documentation index at: https://sequence-0fb8d9e6-api_docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Checkout UI

The SDK comes with a default Checkout UI that we recommend starting with and customizing for your game.

## Working with the Built-in Checkout UI

We've provided a `CheckoutPanel` as part of our Boilerplates assembly. As with the rest of the boilerplates, these are accessed via our `BoilerplatesFactory`, see [Bootstrap Your Game](/sdk/unity/bootstrap) for more info.

In short, with the `CheckoutPanel` prefab located at `Assets/**/Resources/Checkout/CheckoutPanel`, you can easily open the `CheckoutPanel` using the `BoilerplateFactory`:

```
(CheckoutPanel, CheckoutPage) checkoutUi = BoilerplateFactory.OpenCheckoutPanel(parentTransform, checkoutHelperInstance, fiatCheckoutInstance, optionalOnCloseAction);
```

where checkoutHelperInstance implements the `ICheckoutHelper` interface and fiatCheckoutInstance implements the `IFiatCheckout` interface.

There are currently two implementations of `ICheckoutHelper` available to you, `NftCheckout` and `ERC1155SaleCheckout` for Secondary Sales Marketplaces and ERC1155 Primary Sales respectively. An implementation for ERC721 Primary Sales is coming soon.

`SequenceCheckout` is currently the only implementation of `IFiatCheckout` available; it supports both Secondary Sales Marketplaces and ERC1155 Primary Sales; ERC721 Primary Sales support is coming soon to `SequenceCheckout`.

## How it Works

It can be helpful to understand how the Checkout ecosystem fits together, especially if you want to build your own custom checkout panel/modal logic.

This diagram should help you reason about how the system is laid out.

<img src="https://mintcdn.com/sequence-0fb8d9e6-api_docs/CmKz04BVDGuy1x-Z/images/unity/ERG_SequencePayModal.png?fit=max&auto=format&n=CmKz04BVDGuy1x-Z&q=85&s=19bbfe020c0a97bbf55fd851e190cba6" alt="ERG Diagram" width="2359" height="1233" data-path="images/unity/ERG_SequencePayModal.png" />

[Source](https://github.com/0xsequence/sequence-unity/blob/Feature/marketplaceCheckout/Packages/Sequence-Unity/Sequence/SequenceSDK/Marketplace/ERG_CheckoutModal.mmd)

This, along with the `CheckoutPage` (and related) source code should serve as a great reference should you choose to write your own custom UI logic.