A 2010 IGF finalist for Excellence in Design, Cogs is a combination of sliding puzzles with mechanical puzzles. You know what sliding puzzles are, even if you don't immediately grok the term: There those stupid little things consisting of plastic squares arranged in a grid with one space left out. You slide the squares around to make a picture. Like a 2-D Rubik's cube, with none of the algorithmic complexity of the cube.
Cogs adds mechanical puzzles; some squares have gears on them. Somewhere on the puzzle is a rotating gear, and you have to slide your gears around to do something -- sometimes simply to get a target gear to rotate, sometimes something more complicated, like arranging gears with hammers on them to strike bells in a particular sequence. Sequencing then becomes a major challenge, because you have to arrange the gears in such a way that the hammers are poised to strike at the right moment, and in the right way. In addition, some puzzle are arranged over the surface of a 3D object, which you can rotate with the right mouse button.
In other words, Lazy 8 has taken sliding puzzles + gears and run as many changes on the basic concept to come up with puzzles -- some 50 in the full game, with 8 in the demo. They've also spent a lot of effort on the graphic design and intermediate menus so that the app is visually impressive and highly polished.
I like many puzzle-style games, but I have to say the results here leave me cold. I'm not keen on sliders, to start with, and the mechanical aspects don't strike me as particularly charming.