The age and gradual evolution of sire means that it is a large program (over 400k lines of code), and the sire API contains a lot of functionality. During the 2010s it was found that it was difficult for researchers to know what functionality was available in the program, or even how to use it. In 2022, as part of the move to OpenBioSim, it was decided to give sire a complete refurbish and refresh. The original C++-inspired Python API was moved to the sire.legacy submodule, and a new fully pythonic API was created. This work was undertaken using a tutorial-driven development process . Tutorial-driven development involves writing the tutorial for how to use a program first, and then use that tutorial as the guide to write the code that makes the tutorial work. The rationale for this process was twofold: