After a longer-than-planned hiatus, let’s jump back in. Last time I discussed the design throughline, the central concept underlying game play, as one of two fundamental elements I want to determine as the very first step of creating an RPG.
During the design process, the design throughline becomes a benchmark against which I test new rules. It's easy to get sidetracked when designing a subsystem and lose track of the entire rules set's ultimate purpose. To do this it often becomes necessary to articulate additional principles that flow from the design throughline. GUMSHOE's design throughline concerns the facilitation of investigative play. For this reason it seeks to emulate mystery-based fictional sources rather than simulate reality using a physics engine. It aims to be simple, to allow players to focus their brainpower on the overarching meaning of the clues they assemble. In turn, for both of those reasons, it strives to make its rules player-facing. For example, rather than have adversaries roll to see if they detect you when you're hiding, players roll to beat a Difficulty, expressed in the adversary's stats, to see if they've successfully hidden.
D&D doesn't do that, which makes sense, because Dungeons and Dragons is a game about killing monsters and taking their stuff. Having the stats for monsters operate independently of, while interlocking with, the stats for the characters, fits that game's implicit design throughline.
Sometimes I find myself falling back on the core assumptions of previous games. They're familiar and understandable to current players. Compromises with the design throughline may sometimes be justified for this reason: people can absorb only so much new stuff in one go.
As I revise a rules set—either during original design or over time in follow-up products—I often find myself altering material to bring it line with the throughline. Sometimes it takes a while for the implications of the throughline to become clear. We've implemented the player-facing principle more consistently over GUMSHOE's various iterations, as it has become clearer to us.
When a rule causes trouble, or starts feeling wrong, I ask myself if it has taken on a logic of its own at odds with the design throughline. The first iteration of GUMSHOE space combat got away from me because I fell into a level of detail that, while not exactly simulative, set aside the simplicity and abstraction found in the rest of the system. The new version succeeds by back to the design throughline and its implications and restoring those qualities.