Conception Katana Zero was developed over six years by the
indie game creator Justin Stander under the studio name Askiisoft. It was Stander's first commercial game; his previous projects, such as
Tower of Heaven (2009), had been smaller
freeware games. After seeing the success of
Terry Cavanagh's
VVVVVV (2010), Stander concluded audiences only pay attention to indie games if they are being sold. Cavanagh, like Stander, had started off making freeware games, but none were as successful as
VVVVVV.
Katana Zero originated from Stander's desires to create a larger project that could be sold commercially and tell a story. He used the
GameMaker Studio 2 game engine and spent the first two years building simple
prototypes. The game was a means of expression for Stander outside schoolwork and he spent most of his time at college developing it. The total budget was 60,000, which Stander noted was quite small for a game of
Katana Zero scope. Stander decided to develop a
Nintendo Switch version immediately after the system was unveiled because he saw it as a good console for indie games. The one-hit-kill gameplay was frequently compared to another
Devolver Digital-published game,
Hotline Miami. Stander said he only played
Hotline Miami once and did not remember its gameplay, but acknowledged it may have subconsciously influenced him. When developing small freeware games, he could scrutinize minute details, which would result in him spending a year to make a short, 20–30 minute game. The script is credited to Stander and Eric Shumaker, with additional writing by Sterling Nathaniel Brown and Ian Goldsmith Rooney. As Stander developed
Katana Zero focusing on one element at a time, he only had a basic plot summary by the time he finished outlining all the levels. Elements Stander conceived early on included a protagonist who was "sort of trapped in their situation, because those always make for good main characters in action games," and a disagreeable psychiatrist whom players would dislike. The story structure was inspired by
Hotline Miami, in which the player character is directed to kill by mysterious phone calls, and its
themes include
drug addiction and
mental health. Stander hesitated to deal with such topics as they had never affected him, but after some research, felt he could treat them respectfully. Additionally, Stander felt an assassin like Zero would not wait to listen to a villain justify their schemes. He was conscious speedrunners would skip all the dialogue and included in-game consequences for interrupting constantly to create a sense of realism. Kiley and Lodewijk attempted to reflect Zero's changing psyche and moods in their music, such as when Zero experiences Chronos withdrawal and snorts
cocaine in a limousine. Stander sent Kiley and Lodewijk screenshots,
concept art, and notes describing the atmosphere he was aiming for, occasionally alongside an existing piece of music for reference. while Lodewijk used vintage
synthesizers and
drum machines such as the
Akai MPC. While he did edit some tracks using his computer, Lodewijk described his process as "old-fashioned" and estimated 95% of his music was composed using vintage synths. Stander attempted to synchronize the music with the gameplay by having Zero turn on a
Walkman at the beginning of each level, changing the music when Zero takes his
earbuds out to talk to an NPC, and slowing down the music when the player uses Chronos. ==Release==