The gameplay of Stacking is best described as a Puzzle Adventure, something of a mix of the old PC game Messiah and the Lego franchise games that are so ubiquitous now. In this particular universe, we find ourselves in a sort of Steampunk Victorian era that is entirely inhabited by a wide variety of those Stacking Santas you probably saw at your grandmother's house growing up (you might also know them as matryoshka dolls).
The story of Stacking is told through silent-film vignettes complete with intertitles with the narrative, and centers around the Charlie Bucket-like Charlie Blackmore. Master Blackmore is the tiniest doll in the universe and after his family is kidnapped by the evil Baron, he sets about getting them back and putting a stop to the outlandish child labor practiced by the Baron and his cohorts. Obviously Charlie is too tiny to take on this task alone, but in a world of stacking dolls, solutions are only a stack away.
Thus the charm of Stacking is revealed. At the core, this is a simple game consisting of around 20 puzzles spread over 4 levels that you can blast through in a few hours. The beauty in the design is just how many ways you can solve each puzzle. See, there are dozens upon dozens of different types of dolls that come in six sizes and every one of those dolls has a unique action they can perform. The esoteric powers can range from flying to farting to playing violin to seducing other dolls. Half the fun of the game is just mucking about hopping into new dolls and seeing what they do and how they interact with each other. Every puzzle in the game has from 3-5 "named" solutions, and while you only need to find one to advance, the meat of the game is coming back to find all the others after. You'll be surprised at the different ways you can find to spoil everyone's caviar dinner or disrupt a safari.
As you travel from a train station to a cruise ship and a zeppelin you'll find more and more types and sizes of dolls, including many unique ones with exceedingly wacky powers. Often puzzles will require you to make an entire nest of dolls that make a certain "set", such as families or a film crew, or to quickly use two dolls in a combo, like a fire hose spraying water and a cold-air blaster to freeze it into ice. Most puzzles will have an obvious solution and a doll for it wandering nearby, and usually it isn't too hard to figure out all the possible solutions to a puzzle rather quickly. In the event you do get stuck you can access a series of three increasingly direct hints for each potential solution, with the third essentially telling you exactly how to solve the puzzle.
Since the main part of the game won't really challenge you, Double Fine made up for that by making a ton of optional challenges. In each area, there are 32 uniques dolls to find, a dozen "hi-jinks" which are ways for dolls to fuck with other dolls (fart on 5 dolls, head butt 5 mime dolls, things like that), and of course general mayhem to perform by experimenting with doll interactions. What you won't find a lot of is overt humor that you might expect to given the game's pedigree. Most jokes are told through conversations with other dolls, which often change depending on which doll you are controlling. The humor here is a little more subtle and downplayed than something like Psychonauts, and you have to work a little harder to get to it.
I can't deny that the art style and sense of fun are both great upon first impression, but as the game went on, I found that it wasn't quite deep enough to keep me riveted after I had seen most of the dolls. Yes, there is an undeniable charm of unstacking a deep stack and watching as the five dolls all queue up and hop back to whence they came from in a cute little line like baby ducks. Too bad the story cutscenes with the silent-film were more dull and intrusive than a welcome sight, leaving me yawning and disappointed. Much like Costume Quest, the game probably will wear out it's welcome before you finish, and unlike CQ, this game didn't keep a smile on my face the whole time. Once you go back and figure out all the puzzle solutions, there isn't any reason to ever come back to the game. A nice Sunday afternoon diversion for families, but certainly not an instant classic.