However, there're certain tradeoffs in that comes along with implementing an interface that relies upon direct manipulation. The active blocks of Topobo embedded with kinetic energy only allows the duplication of movements physically created by the user. The designers at the Tangible Media Group made a tradeoff between reality and versatility. The range of motion of the Topobo piece and the speed at which it operates are solely dependent upon the physical input done by the user. If the user wishes to have one section of the model spin in a continuous fashion for a set amount of time, he or she would have to physically rotate that section of the model for the said time in order to reach the desired movements for the model. However, if the user was using a traditional GUI where all the movements were programmed into the Topobo blocks, then physically difficult to achieve movements such as continuous spinning or extremely fast rotation are easily accomplished with a simple line of code. The designers have favored a reliance on direct manipulation of the Topobo pieces applying naive physics.
According to the definitions of TUIs stated by Kenneth P. Fishkin in his A Taxonomy for and Analysis of Tangible Interfaces, a "2D taxonomy is fruitful, one that uses as its dimensions embodiment and metaphor" . So for Topbo, it can be categorized as a full embodiment user interface, where "the output device is the input device; the state of the device is fully embodied in the device" . As an assembly system with kinetic memory, any changes/interactions done on the Topobo blocks are reenacted on the blocks themselves. If you rotate one section of the block by 30 degrees, the blocks will rotate the same section by the same degrees. Both the input and the output in this care are physical.
In the Topobo assembly system, users manipulate and change the blocks on the structure, and their motions are recreated right back at them with the same blocks. This is a type of "Really direct Manipulation". There's no metaphor needed to describe the input and output process of using this TUI, and thus it can be categorized as a full metaphor.
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