If PlayerPrefs, INI files, XML files, or JSON files don't meet your needs, then binary files might be exactly what you're looking for. If you don't want to save data that gamers can open, read, and change, binary is the preferred option. Binary files typically produce the smallest file size and are non-readable. Their disadvantage is the difficulty of debugging (because you cannot easily verify their contents), and other applications cannot import and parse them because they conform to no other established standard; they don't know how your data is structured. To get started with using binary files, add the serializeTransformBinary.cs script file to your project; comments follow the code:
using System.Collections; ...