In mid-1980s, a small company called Mark Data Products released 6 parser-based graphic adventure games similar to early Polarware and Scott Adams titles.While the games are reasonably successful on Tandy's CoCo computer, the IBM PC versions did not achieve the same level of success. While the graphics are quite good at the time, the parser is quite primitive - only simple verb+noun constructs such as GET HAT are understood, and some verbs that are common in IF games such as SEARCH are not always recognized. Fortunately, the games make up for primitive parser with well-written plot, fun characters, and some clever puzzles.
The plot of The Vortex Factor: "What is it? What secrets does it hold? The seeker of treasures through time and space must find out! From the coliseum of ancient Rome to the futuristic world of tomorrow ... join us in this unforgettable odyssey."
Thanks to the generosity of Bob Withers, co-creator of these underdogs who put both the games and their source codes up on his website for free download, you can now experience a forgotten past of the early days of adventure gaming. All are recommended, but if you want the best of the bunch, I highly recommend my personal favorites: Trekboer and Calixto Island.