Comment by Joe_Cool

And if something didn't work he included a complete debugger inside "Apple II Machine Language Monitor" in ROM so you could always just disassemble and poke at things, pipe disassembly to the printer, read memory, change code, add own macros to CTRL+Y and rerun stuff. All that without extra software or a massive pile of printed assembly.

from BASIC:

  CALL -151 (short for CALL 65385, but BASIC can't handle unsigned INT so that wouldn't work)  
  F666G  

and the machine is your playground.