ST-Sim version 2.1 is now available for download at https://apexrms.com/projects/stsm. This version adds additional fields to the randomization of initial time since transition (TST) values for each cell.  Users can now specify initial TST ranges, including minimum and maximum values, according to stratum, secondary stratum, transition group, and state class.  This version also adds field display behaviour for the state class editor window which is consistent to that of the probabilistic and deterministic transition windows.