# Multi-Platform Project

Developing a multi-platform game project comes with unique challenges and trade-offs. This article explores common questions and practical solutions for fresh game developers. While no single code base can cover every platform, careful planning and smart engineering can make multi-platform development much more manageable.

### Introduction

It’s a common myth that one code base will run seamlessly on all platforms. In practice, multi-platform projects rely heavily on conditional compilation—using script defines, build targets, and sometimes separate branches—to handle platform-specific requirements. This article explains these challenges and introduces several approaches to streamline your workflow.

### Considerations

#### Platform vs. Build Target

* **Platform:** Refers to distribution channels (e.g., Steam, Epic Store, Game Pass) as well as hardware (e.g., Xbox, PlayStation, Switch). A platform often has its own API or service requirements.
* **Build Target:** The actual operating system or device environment (e.g., Windows, Mac, Linux, Android). A single build target might support multiple platforms, but each can demand specific code.

Using conditional compilation in the editor can lead to missing objects or broken references. For example, disabling a Steam API block for testing can cause Unity to strip out important configuration data when the scene is saved.

#### Unit Testing Challenges

Testing in a multi-platform project is tricky:

* **Editor vs. Build:** The code in the editor (most inclusive) can differ substantially from the stripped-down version produced for a specific build target.
* **Platform-Specific Code:** Switching the editor build target may remove necessary scripts, causing test failures or reference losses.

### Solutions

#### Parallel Development

A rigorous ALM/DevOps setup allows you to maintain parallel branches for each platform. This approach lets you integrate common code changes easily, but it requires strong engineering discipline and robust tooling.

#### Build Service

For smaller projects or those with limited platform-specific code, a build service can manage platform-specific compilation. Typically, you keep your editor set to a common target (e.g., Windows or Mac) and use the build service to generate versions for each platform. This minimizes the risk of the editor stripping out necessary code.

#### Multi-Project Approach

Though error-prone and labor-intensive, maintaining separate Unity projects (or similar structures in other engines) for each platform can be a solution when advanced tooling isn’t available. This “poor man’s parallel development” requires manually syncing common code, but tools like asset export/import can help streamline the process.

### Engine-Specific Examples

#### Unity Example

Unity projects often face challenges with conditional compilation. Consider the following approach that uses editor-specific code and script defines:

```csharp
// This code is always included in the Unity Editor
#if UNITY_EDITOR
#define STEAM_PLATFORM
//#define EPIC_PLATFORM
#endif

public class PlatformManager : MonoBehaviour
{
    void Start()
    {
#if STEAM_PLATFORM || UNITY_EDITOR
        // Steam-specific initialization
        Debug.Log("Initializing for Steam.");
#endif

#if EPIC_PLATFORM
        // Epic-specific initialization
        Debug.Log("Initializing for Epic Store.");
#endif
    }
}
```

This snippet shows how to enable platform-specific code during development while keeping the editor configuration intact.

#### Unreal Example

In Unreal Engine, preprocessor directives and macros are used to manage multi-platform code. For instance, you might use platform-specific sections in your C++ code:

```cpp
#include "PlatformManager.h"
#include "Engine/Engine.h"

void UPlatformManager::InitializePlatform()
{
#if PLATFORM_WINDOWS
    UE_LOG(LogTemp, Log, TEXT("Initializing for Windows."));
#elif PLATFORM_XBOXONE
    UE_LOG(LogTemp, Log, TEXT("Initializing for Xbox One."));
#else
    UE_LOG(LogTemp, Log, TEXT("Initializing for default platform."));
#endif
}
```

Using Unreal’s built-in platform macros (such as `PLATFORM_WINDOWS` or `PLATFORM_XBOXONE`) ensures that the appropriate code is compiled for each target.

#### Godot Example

Godot handles multi-platform development by allowing you to query the platform at runtime and use conditional logic. For example:

```gdscript
func _ready():
    var platform = OS.get_name()
    if platform == "Windows":
        print("Initializing for Windows.")
    elif platform == "X11":
        print("Initializing for Linux.")
    elif platform == "OSX":
        print("Initializing for macOS.")
    else:
        print("Initializing for default platform.")
```

This GDScript example demonstrates a runtime check to adjust behavior based on the detected platform. Although not compile-time, it helps keep platform-specific logic organized.

### Conclusion

There is no one-size-fits-all solution for multi-platform development. Whether you choose parallel development, a build service, or a multi-project approach, each method has its own trade-offs. By understanding the distinctions between platform and build target and leveraging engine-specific tools, you can better manage your project’s code base. This guidance should help you make informed decisions and streamline development across Unity, Unreal, Godot, and beyond.