-- Overview of layers
0-9: infrastructure independent of this program
10-29: level 1, the SubX subset of the 32-bit x86 ISA
30-39: level 2, moving past counting bytes with operands and labels
See layer 29 for the description of 'level'.
--- Overview of tracing depths
0: errors
1-98: app level traces for different SubX programs
99: low-level details of the VM