Stacking

The player controls Charlie Blackmore, the smallest doll in the world, who is attempting to reunite his family that is being forced to work for an evil industrialist named The Baron. Charlie is able to jump inside dolls that are one size larger than he and control them, as long as the larger doll is facing away from him. If the player already controls a stack of dolls, that stack can jump into a one-size-larger doll as well. The player can also unstack the dolls at any time in order to enter dolls smaller than his current stack.

Certain unique dolls, outside of Charlie, have their own special abilities—such as the ability to unlock doors, float to higher locations, or lure other dolls around, which can be used by the outermost doll. Thus, the player must stack and unstack the set of dolls possessed by Charlie to solve puzzles throughout the game. Later puzzles may require the use of multiple dolls to combine their skills.

Set in a fictional version of the industrial age, the story begins with William Blackmore, a professional chimney sweep, leaving his family to take a job under a powerful industrialist, the Baron. A few months later, with William having failed to return and the family deep in debt, the four Blackmore children (Albert, Agatha, Abigail, and Archibald) are forced into apprenticeships by the Baron's agents, leaving the youngest, Charlie, alone with his mother Agnes. A few weeks later, a pigeon arrives with a letter from Albert, who reveals that the Baron has split up him and his siblings, forcing them to work as slaves. Charlie subsequently sets out to rescue them, recruiting a friendly hobo named Levi to help him set up a hideout in an abandoned section of the Royal Train Station, where a strike has forced the station's management to use Albert and other children as coal shovelers.

Charlie sets up a meeting between the strike leader and representatives from the Train Guild, breaking the strike and freeing Albert. Another letter, this time from Agatha, then leads him to the Baron's private cruise ship, the Commodore Perry, which is currently embarked on a never-ending voyage. By turning a small group of wealthy and influential passengers aboard the Perry against the ship's captain, Charlie forces him to return to shore, allowing Agatha to return home. A third letter leads Charlie to slip aboard a massive zeppelin hosting an international summit on whether or not to ban the use of child labor, which the Baron has rigged by abducting the ambassadors opposed to him.

Stacking is the second game, following Costume Quest, to come from Double Fine that was initially created during an "Amnesia Fortnight" event during Brütal Legend's development period. Tim Schafer had used the Fortnight during a time where the fate of Brütal Legend's publication was unclear, dividing the company into four teams to prototype smaller games. The game's creator and project lead is Lee Petty, who had been the art director for Brütal Legend. Petty had wanted to create a contemporary adventure game, maintaining the characters and stories while reinventing the normal point-and-click interface used for such games.

After observing his daughter playing with matryoshka dolls, he realized that the dolls themselves could be the characters, the inventory, and the action verbs at the same time. Petty and Schafer later reflected that the use of dolls, a common toy, would help to make the game appealing to the casual player, as they would quickly understand the mechanics of stacking and unstacking, while still having an allure for hardcore players with deeper gameplay mechanics. The idea of using these dolls would later be of benefit in production, as the basic structure of the doll model in the game's engine could easily be reused for the more than one hundred unique dolls within the game. Schafer assisted in helping Petty to write the game's story and to design some of the puzzles.

Stacking has received largely positive critical appraisal. Most reviewers commented on the short length of the game if one simply progressed through the story without exploring any of the alternate solutions or side puzzles, and may be considered too short a game for the $15 price. Many felt that with the full exploration possible within the game, Stacking is well-worth the price without becoming too long or repetitive; Chad Sepieha of The Globe and Mail stated that the game is "a great example of what a $15 digitally distributed game can be", while Justin Haywald of 1UP.com found strong preference for the way that Stacking "condenses a fun experience into several great hours rather than overextending itself".

The game's core gameplay was considered to be very accessible, in part due to its alluring visuals. The controls were considered simple enough to be easily taught to a casual player, and provides enough hints so that the player rarely will be stuck to progress in the game. The use of multiple solutions to solve various challenges was praised; as stated by Jeff Marchiafava of Game Informer, providing multiple solutions helps to "[solve] one of the most common problems with the [adventure game] genre" as players do not have to guess at one specific line of thought programmed by the developers. The multiple solutions also provide a means of enticing players to seek out all solutions, as finding the solutions can be "logical and rewarding to work out", according to GameSpot's Carolyn Petit.