Can also read a DSSP file to determine secondary structure. Ability to save and easily switch between multiple views of a structure. Ability to define and independently manipulate subsets of atoms. Subsets may overlap, and can by dynamically re-defined. Powerful history and macro mechanism for creating shortcuts to complex scripts.
Command line accepts and translates environment variables.
Can also set environment variables from the command line for spock and any subprocesses. This allows for user customization of commands and definition of shortcuts. Calculate and display axis of helices, and major moment of sheets. JPEG is no longer supported since it lead to version-skew problems on many platforms, and JPEG isn't a good format for the type of images spock produces anyway. Powerful selection mechanism to easily specify groups of atoms or molecules.