So, I am developing a game called CSS Hero, it is an android game, to learn CSS in a fun way. It teaches users the basics of how CSS work. Each level gets more complex, building on what they’ve learned in previous lessons.

I need to figure out what to write in the System Requirments Section, for both the Functional Requirements and the Non-Functional Requirements.

Can someone help me with that?

Sorry, I don't know what defines the functional requirements and the non-functional requirements, but if it's Android only then I would start by looking at the minSdkVersion and the targetSdkVersion in the build.gradle file. Looking those up should lead you to, what I believe to be, the functional requirements.

Ok, I'm going to explain as though you haven't started developing the game yet.

In Functional requirements, u need to write down everything that your game must be able to.

// pseudo example
Functional Req
--------------
- My game must be able to read a CSS file and convert it to an image
- My game must be able to add scores and display it on the scoreboard
- My game must support all kinds of sounds to tell player what he/she is doing with my CSS ...
- My game needs to talk to OpenGL API 
- etc...

The summation of all these Must-Dos is what makes up the functional requirement -the behaviour- of your game and usually this list goes hand in hand in with your System design. It is the make-up of your game software.

In non-Functional requirements, u need to write down everything that relates to the technical parts that your game needs to work. Usually, everything in this list would be the minimum requirement of each list item that is needed for your game to work.

// pseudo example
Non-Functional Req.
-------------------
For my game XYZ to run, it minimally needs the following: 
- Tablet Samsung min version XXXX (for cost predictions)
- 1 octa core processor running at 1.xGHz (for performance)
- Android min version XXX (for reliability)
- Antivirus XXXXX (for security)
- OpenGL SDK min v4 ...
- CSS version ...
- 3 MB 
- 1 SD card
- 1 cow 
- 2 birds and a lump o' cheese :)
- ... etc...

So effectively, this list outlays the architecture of your game system

Hope this clarifies it a bit and gets u going;

That's it … all the best ?