УРОК: Интегриране на Steam Cloud в Unity проект by Prime Games Bulgaria

With the highly competitive scene that is the indie game market today, anyone who has even the slightest edge might end up at the top percentile of successful games. When you release your game out in the wild any kind of integration specific for the online stores you are selling on is turning from ‘nice-to-have’ to mandatory and Steam is no exception.

Any feature your game has on Steam such as Achievements, Cloud Saves, Trading Cards, Controller Support, etc. will help your game list better on the store. After all, all the above are filter options when it comes to searching for the next game to play/buy so why not having your game appear there as well?

Prerequisites

A Unity build already done and submitted on Steam.

What is Steam Cloud?

Steam Cloud provides an easy and transparent remote file storage system for your game. Idea is that you can sync data (e.g. unlocked checkpoints, game state, settings, save/load files) between different PCs that the player has the game installed on.

Auto-Cloud for Unity applications

Focus of this article is the Auto-Cloud setup. Files specified in the Auto-Cloud configuration or written to disk (created, modified, deleted, etc.) using the Cloud API will automatically be replicated to the Steam servers after the game exits.

Part 1: Reading and writing files from within Unity

Decide what type of information you are going to store in the Cloud. In my example, I’ll create a serializable class with some generic game properties.

[Serializable]
public class SteamCloudPrefs
{
    // Game Data //
    public string hp = "";

    public string ammo = "";
}        

This is an oversimplification of the data that must be stored but it will work for our example’s needs.

Next is the save and load file mechanism.

using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using UnityEngine;

public static class SaveLoadFile
{
    private const string FILENAME = "/SteamCloud_BattleForMurk.sav";

    public static void Save(SteamCloudPrefs steamCloudPrefs)
    {
        BinaryFormatter bf = new BinaryFormatter();
        FileStream stream = new FileStream(Application.persistentDataPath + FILENAME, FileMode.Create);

        bf.Serialize(stream, steamCloudPrefs);
        stream.Close();
    }

    public static SteamCloudPrefs Load()
    {
        if(File.Exists(Application.persistentDataPath + FILENAME))
        {
            BinaryFormatter bf = new BinaryFormatter();
            FileStream stream = new FileStream(Application.persistentDataPath + FILENAME, FileMode.Open);

            SteamCloudPrefs data = bf.Deserialize(stream) as SteamCloudPrefs;

            stream.Close();

            return data;
        }
        else
        {
            Debug.LogError("File not found.");
            return null;
        }
    }
}

There are several key moments that I would like to outline.

BinaryFormatter is essential for storing the data in a non-readable format. You do not want the players messing around with it and obtaining what could be sensitive data for your game. Rather, the file would look something like this if opened:

0001 0000 00ff ffff ff01 0000 0000 0000
000c 0200 0000 0f41 7373 656d 626c 792d
…             

FileStream is standard C# for input and output of data streams.

Unity provides you with Application.persistentDataPath which contains the path to a persistent data directory. You will be using it for storing your files locally on the disk. The location varies on different OS, that’s why it’s important to note down in advance what exactly is the path based on your needs. In my case I store them in %USERPROFILE%/AppData/LocalLow/CompanyName/GameName (on Windows). Based on your installation this is your user folder on your local drive, e.g. C:/Users/My-User/AppData. The folder may be hidden by default so remember to view your hidden files. On OS X (my Mac) I have the location at ~/Library/Application Support/unity.CompanyName.GameName

Adjust your game code so it stores the necessary data upon an event (e.g. when a Scene gets destroyed).

Make sure that it obtains it from that file on startup and uses it to update its state.

public class Main : MonoBehaviour 
{
    public SteamCloudPrefs SteamStorage = new SteamCloudPrefs();

    private void Start()
    {
        if (SaveLoadFile.Load() != null)
        {
            SteamStorage = SaveLoadFile.Load();

            LocalStorage.hp = SteamStorage.hp;
            LocalStorage.ammo = SteamStorage.ammo;
        }
    }

    private void OnDestroy()
    {
        SteamStorage.hp = LocalStorage.hp;
        SteamStorage.ammo = LocalStorage.preBatammotleState;

        SaveLoadFile.Save(SteamStorage);
    }
}       

Sample Mono class that can serve as your hub for storing and loading your data.

Test and if all works, you are now half-way there. Next step is Steam!

Part 2. Steam Auto-Cloud config

When your Unity application stores and loads the config files successfully you have what I would call ‘a black box’. Your application has the single responsibility to read and write the file from within that directory. Your next task is to sync this directory’s contents with Steam’s servers and make sure it is the same across devices.

I highly recommend reading end-to-end the official Steam documentation here: https://partner.steamgames.com/doc/features/cloud

Once you are familiar with it, you can proceed with configuring your app.

The idea is to let Steam do the syncing automatically. It will check the directory and upload its contents to its servers once you exit your game. Before you start the game, it will obtain any new files and download them to that directory to keep things on track. Even if you lack internet connection, upon next game bootup Steam will warn the player if a newer file version than the one in the cloud exists locally and prompt him with a pop-up window to choose which one to use and overwrite the other.

Part 2.1. Go to Setting up Steam-Cloud page from within Steam

Part 2.2. Setup User Quota

Set the number of files you want to sync and the maximum file size it should allow.

Part 2.3. Enable Auto-Cloud config

Part 2.4. Setup Directories

Remember you’ve written down your directory paths earlier? It’s time to put them into usage. Scrolling down you’ll see the directory setup.

Setup the main directory first for the preferred OS (I imagine that would be Windows in most cases).

After that you can create Root Overrides for the additional OSes you support. The overrides will replace the first part of your root path and the second part you’ll have to fill up yourself. It’s straightforward. Just pay attention what it says in the preview under the input boxes.

Part 2.5. Testing

Finally, you must test if all is fine and dandy. Follow the steps for Pre-release Testing from Valve’s docs https://partner.steamgames.com/doc/features/cloud

Voila!

Good luck on your Steam releases and may your stamina never fail 😊 If you have questions, post them in the comments section bellow and I’ll try to answer them as best I can.