Within
TIS-100, the player is said to have come across a malfunctioning TIS-100 computer ("Tessellated Intelligence System") and its manual, based on early computers of the 1980s. The computer is presented to the player as twelve separate processing nodes laid out in a four-by-three grid. Each node has a single
processor register to store a numerical value as well as a backup register. Nodes also hold their own
assembly language program as entered by the user. The assembly language, a simplified version of real-world assembly languages, allows the node to accept external input or a numerical value sent from an adjacent node, perform basic math and logic operations, store and backup the current data value, and then send results to an adjacent node or to the program's output. Later puzzles introduce stack nodes and an output to a simple 5-color graphics display. The player is presented with a series of puzzles that require them to program the nodes to perform specific actions on a set of numbers from one or more input terminals to produce pre-determined output at other terminals. For example, one task requires the player to double the value of the input at the output terminal. The game presents the list of inputs and the target output values that it is expecting and requires the players to develop the code for each node to match this; if during execution the output nodes receive unexpected outputs, the player will have to rework their solution. Not all nodes are available in certain puzzles, so the player will need to route around these nodes. The game offers the player the ability to step through the execution of the code and insert
debugging statements to determine logic issues within their code. Once the target output conditions are met, the player is considered to have solved the puzzle. The nodes that are disabled in puzzles contain cryptic messages related to the narrative of the game and which contain more information that can be accessed when the entire game is completed. As with previous Zachtronics games such as
SpaceChem and
Infinifactory, once the player completes a puzzle, their solution is compared to other players through online leaderboards. The player is ranked based on the number of nodes used, the number of instructions within their code, and the number of
instruction cycles used. The game allows the player to return to earlier puzzles to better their solution. The game launched in
early access in June 2015 with about 25 puzzles within the game, and another 25 were added by the time of its official release the following month.
Computer architecture A TIS-100 "machine" is made up of 12 interconnected nodes on a grid, either a compute node or a
stack memory module. Each compute node may hold 15 instructions and each memory node may hold 15 values. Nodes at the top or the bottom may be connected to external sources of input or output respectively. Each TIS-100 compute node has two registers called ACC and BAK. ACC is used by most instructions, while BAK is only accessed by two instructions, one for swapping and one for copying. The instruction set contains 13 documented instructions for arithmetic, basic flow control (conditional jump), no-op, and sending data to adjacent nodes. The game also includes undocumented instructions, with
HCF (reboot game) being the first known undocumented instruction. The TIS-100 architecture has also been implemented outside of the game in an emulator, intended to be used as an
esoteric programming language. ==Development==