Its a map made with unity which means, you can make your own objects in your custom map such as your own planets around or a race track, or a football game etc. there are no limits whatsover. Heres a picture of my custom made world with planets and my own made race track:

As you can see in the image there is my race track and planets in the background. I will show you now how to set up unity to make mod maps.

You first will need to download MCNWorld[drive.google.com]. Only the latest mcnworld will work. If your version is low you have to go to this website[hrpbk2.wixsite.com] and click the link with UnityEditor on its right. Example:

You will also need to download UnityEditor[store.unity.com]. It can be any unity. It can also be personal.
Once you download both of them open unity and make a new project. It might ask you to login so you might have to register here[www.google.ie]. Once you make a new project go to Documents/Your project name and extract McnWorld. Once youre finish extracting make sure youre unity is open. Open up McnWorld(with unity icon) and it will load up in unity. it will say extract. Make sure you press all and press extract. Now youre good to go.

Now you can press scenes on file explorer and press emptyworld. You can remove water or terrain if you want but Dont remove world. World is your container of objects so make sure its there. Click on world and you'll see the script and objects assigned to World. Make sure theres a ground on the level and make sure its in World. If a object is outside World it will be removed. So always be sure to have all your objects in World. Theres another issue in unity for machine craft map. Every object should have Standard or Custom shader from machinecraft but i do recommend standard since it doesnt glitch. If the shader is incorrect the object will come up as a purple so make sure you have a shader. NOTE:The spawn point is at 0,0,0 if there isnt any spawn prefabs. Also rename your spawn prefab to Spawn00, Spawn01 etc. instead of Spawn or, as the creator of machinecraft said in his manual file it can be a Empty object called SpawnNN. so make sure you dont place your ground far away or else your map is ruined. You can use prefabs freely and place planets,road,ship and so on. Make sure you save your map as a new scene or else you cannot copy the emptyworld(unless you export it into unity) You can press the play button and have a look around the map. Press F4 to switch between day and night.

On the top there is a button saying McnUtil. This button is really useful. There are many buttons once your press McnUtil. Heres a explanation for every button.

• Add vertext colour to selected objects - It give colour information to a object. It might be useful to adding colour to models.
  
• Add PathTracer to selected Objects - Add path to a object(will be useful in later updates)
  
• Prepare for test - Automatically perform settings necessary for animation and physical calculation(Will be useful in future updates)
  
• Rename Gates - Set index of race gates to serial number(for races when you have lots of gates)
  
• Optimize Scene - Clones a scene for you so you can work on and later save it for your originial scene
  
• Build AssetBundle - Outputs scene data as AssetBundle

If you wanna export your scene for use in machinecraft make sure everything is in World and before you press AssetBundle you will have to make a new folder called UserData(Use same caps) and make a folder in UserData called _worlds(no caps) and youre ready to press AssetBundle! Here comes the magic. It builds a file for your scene so you can play it and upload it etc.

If you want to play your scene you have to go to Documents/Name of your project/UserData/_worlds and also open this folder: C://Users\Your User\Program Files (x86)\Steam\steamapps\common\MachineCraft\UserData\_worlds(Just go to your steam folder and go to machine craft) and drag in your scene from unity(it will be called like the scene you saved it as) into your original _worlds folder and you can now test it. Go to machine craft, change map to MOD and you should have a field on top saying world data. Put in name of your world, save and load. It might take a while. Your map should load. Be proud with your first mod map. If you want your map on multiplayer you have to make a dropbox account[dropbox.com]. Once you have a account(or had a account) upload youre world file and wait for the upload to procces. Once its finish proccesing click on the box on the left side of your file(By default it should be clicked automatically) and click Publish and click Create link. Copy the link and paste it on the second field of your MOD map(World data URL field) in machine craft.Remove 0B at the end of your link and change it into 1B Example: dropbox.com/s/Myrandomlink1234/myrandomworld?dl-1B.Now you can load your map on multiplayer! Congratulations!

Not everything works on machinecraft scene so just to be sure dont be surprised when a texture is broken or your model wont appear. Its totally normal and to be honest it is annoying. If you want more explenations on stuff such as races, football you can find it on this pdf file: Click me[drive.google.com]. Its the tutorial by the creator translated from japanese to english. I translated it with my boi google. Hope you understanded this tutorial and have fun making custom maps!