Gears

Plith is a simple puzzle game tuned to a casual level of difficulty, but with nicely rendered graphics and unobjectional music.

Each level consists of a peg board, and some initial arrangement of gears -- typically including one red one and one green one. The objective is to place additional gears on the pegs, so that the red gear will ultimately be able to turn the green gear. The difficulty in doing so is two-fold; firstly, putting a gear on some pegs will prevent a solution; and secondly, you have no control over what type of gear you will be served next. Sometimes you want a big one, and are given a small one, and have to try to find an appropriate place to put it.

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.