"Adventure" is one of my all time favorite (or if not favorite then at least most nostalgic) games. By the way, we *did* have both an Atari 2600 and an Intellivision. Then again, we had a lot more money in those days.
Using "Stonehenge" was a nice touch.
Everyone always says the dragons look like ducks. They're clearly seahorses. But seriously, if it helps you to suspend your disbelief then remember that there's no universally agreed upon image of what dragons are supposed to look like and not all accounts of them in ancient lore clearly describe their physical appearance anyway. Of course, I've never seen any ancient references to swords that use the same word in the original language they use for "arrow"....
