Cogs is, in essence, a collection of 50(ish) sliding puzzles. WAIT, COME BACK HERE! It's also surprisingly fun and relatively varied.
Sliding puzzles are considered tedious because the aim usually is to reconstruct a picture, or a sequence of numbers, meaning every piece has to be at its exact place, and that may cause frustration. But here, you have to align cogs and pipes, and some of the tiles are definitely inter-changeable (with few exception a cog is the same as another cog), so that problem is considerably lowered in most puzzles. Variety comes from the shapes of the boards, the types of cogs or pipes present, the kind of contraption ultimately activated by all those trinkets, double faced boards, bells to ring... Cogs is quite effective at keeping your interest alive. And it must be, because the puzzles are clearly challenging.
Another nice touch, is that each of the 50 puzzles also has two variants, much shorter and easier but with additional constraints (one must be completed in less than 30 seconds, the other in less than 10 moves).
There isn't a story, even though there definitely is a Steampunk meets Da Vinci's codex theme.
Music is forgettable, graphics are nice and clean, but unspectacular. Also, it's a bit disappointing when a 2009 game forces you into a 4:3 screen ratio.
Overall, the puzzle difficulty lied just within my fun zone and the game's uniqueness makes it hard to not recommend to puzzle enthusiasts.