IS anything supposed to happen after i beat all the levels, like do i get anymore or a new store or a harder difficulty or anything. edit: sorry about the typo in Question from the title
The developers are experimenting with URL connected missions or something. It's pretty cool, I'd link you to the level but I forget where it is. Dig through the isotope release thread.
In order for the link to work you have to be updated to the latest 1.2 update. There are harder difficulty modes, you can go into the "switch user" menu and start a new game and then you can select your difficulty. There is also survival mode and online leaderboards to go with it.