The fun doesn't stop there, though — simply wash off the pencil and head to this link from the company for a new puzzle every month. There's also an option to sign up for an email alert when the next puzzle drops, and you can browse past puzzles....
PG is for attracting eighteen-year-olds to see G movies. More at PG and MPAA entries. pH Potential of Hydrogen: -log[H+]. A measure of acidity on a logarithmic scale like the open-ended Richter scales. 7 is neutral, numbers larger than 7 are basic (roughly equivalent term alkaline...