He wasn't hacking. Hal worked for Aph, and Aph contracted with Mattel to deliver console game cartridges.
There was once a contest between Caltech and MIT. Each was to write a program to play Gomoku, and they'd play against each other. Hal wrote a Gomoku-playing program in a weekend, and it trashed MIT's program.
I remember trying to help a fellow student in Manchester University around 1991 and thinking I was deleting a subfolder when in fact I was in their home directory:
rm -rf *
: and deleting everything from their Sun Workstation Unix account. Apologies!
I went to clear some games off a drive to make room for new games, went to type RM -rf ./ and accidentally smacked enter instead of a slash. Wiped out a few games before I could stop it.
Got lucky there was nothing really important on there, and it didn't take long to fix things up. Fortunately, some stuff I was removing was at the top anyway.