Re: A83:'ret'

RET uses the stack, it just pops the program counter.  Make sure you count
your pushes and pops, because the stack is not infinate.

If you want a nice bail-out feature, do this somewhere in the code
(beginning):

 ld (BackupSP),sp

And when quitting, just 'jp Quit'.  This restores the stack and returns.

Quit:
 ld sp,(BackupSP)
 ret

(You need a variable called BackupSP, use this:)
BackupSP: .dw 0