One of my favorite games as a kid was an old PC game called Think Quick. It was a very basic puzzle game where you had to explore a castle and use switches to move barriers around in order to get by. The best part though was the level creator. I spent hours creating my own levels just for my own amusement.
Oh, and Klik & Play has had a few successors over the years, the most recent version being Multimedia Fusion, which has a lot more features including the ability to have scrolling levels.