TIS-100 is a puzzle game about a fictional 1980s computer. The player must repair the computer by reprogramming corrupted code segments, using a limited form of assembly language. Each completed puzzle allows the player to reveal more of the secrets hidden within the computer, allowing them to learn more about its history and purpose.
Each puzzle presents the player with a grid of interconnected nodes and some number of input and output connections. Nodes are either execution nodes, which can run simple programs, or memory nodes, which can store data. Most puzzles involve taking an input value, transforming it in some way and moving it to an output connection. In addition to the base puzzles, there are sandbox modes containing the various node types, allowing the player to create their own programs and experiment with the various instructions. There is also an option to load custom puzzles, although these have to be created outside the game using lua scripts.
The game has no tutorial (aside from some hints included in the very first puzzle), but comes with an instruction manual in PDF form, presented in the style of a technical manual. The player is encouraged to print this and refer to it frequently.
The TIS-100 was initially intended as a single part of a more ambitious game developed by Zachtronic called The Second Golden Age. When development of this fell through, the TIS-100 part of the game was already fully realised, and the developers realised that it could be built up into its own game. TIS-100 entered Steam Early Access on 1st June 2015 and the final version was released on 20th July 2015.