I agree that Hexen would be a better pick for an episode, since Heretic really is essentially a doom total conversion, with the most notable innovation being the ability to store items in an inventory for later use.
Hexen has a fundamentally different game design, with the non-linear hub-based map structure and emphasis on thorough exploration. Also, Hexen brought several interesting technical advancements to the Doom engine. Firstly the custom ACS scripting language which adds much more dynamism to the maps with elaborate scripted sequences and puzzle triggers. Second, there were “polyobjects” which were specially marked sectors that could move and rotate in ways previously impossible for Doom, allowing things like the swinging doors on the first level, or the sliding crusher walls seen later.
My friend and I couldn’t get enough of Hexen and played through it with all the classes on progressively higher difficulties just to get more out of the game, and would do co-op runs over modem, much to the frustration of our parents for tying up the lines 🙂
