Future Features!

This has been keeping me up all night, so just to get my thoughts down I'm going to write this out.
What I plan to add in the near future:

• Save System
• Point System, or Story line?
• More Puzzle types
• Rigid body movement?
• switches and what not

The thing that's been keeping me up has been the save system. I have a sort of Idea of how to tackle this, but here it goes. I'm going to use the playerprefs class to save an integer, this integer will be directly linked to the level completed. So by this method I will be saving only one variable, and in between maps. For instance;

Player clicks "Load Game"> Level Completed variable = 2 > load second level. 

or

Player clicks "Load Game">Level Completed variable = 0 or null > Display message "No Game Started"

My problem is that I don't want a million loading screens for every time in between levels, so I need a variable that won't change in between levels and every time a level is completed it will add one to the Level Completed variable which is saved by the playerprefs class, but I'm getting tired so now my brain is wandering to new problems that didn't exist before, and probably won't exist in the morning. So I say to everyone reading. Goodnight, and also, thanks. ;)