Talking about kongregate, I have a favorite game that is quite interesting.
Its name is ‘Gemcraft’ and it’s a tower defense game(you basically have to defend your house from being attacked by monsters by using the so-called ‘gems’, which you can constantly upgrade). I probably like this game because I used to play different tower defense maps in Starcraft :D.
You can access the game at this link:
This game provides saves. It will save on your computer so every time you come back to play you can continue from the point you left(assuming you saved your progress first).