Alacrity,
I was first attracted to your recruitment for this game for three reasons:
1) You were DMing, and that pretty much guarantees a good gaming experience.
2) You said it was a lunch time dungeon romp... so, I figured light-hearted, explore the rooms, slay the monsters kind of game.
3) You said it was about 18 rooms total and would likely be a "shorter" game.
That all sounded good to me.
I'd agree with Almerin that puzzle-based games are definitely easier around a table, but that you're giving us good clues so far along the way. I don't make any claim that I've got this puzzle figured out. But I do fee like we're getting somewhere.
Anyway, still looking forward to this.
Ayrn