In the early 1980s, Sierra was at the forefront of the move from text adventures to adventures of the graphical kind—first with Mystery House, and later a string of games made in the studio's own Adventure Game Interpreter, like the first King's Quest and its immediate sequels. AGI allowed for sound effects, music, and 16-color vector graphics, depicting protagonists who moved around scenes with the arrow keys. You still had to type "lift plank" and "get ring" to interact with things, but you...