A downloadable reaction/parley system.
Awesome, streamlined system! I especially love that all of the d66 Personalities have mechanical effects, supporting gameplay and not just fiction.
There are a lot of great tools for randomly generating NPC personalities or even motives, but these tools will generally lead to a judgement call of how to interpret these results within the game- which adds another dimension whereby meta-gaming or simple lack of obvious next steps can slow down or outright halt solo roleplaying. Something like the NPC generator tools in Scarlet Heroes could apply here, they're fantastic for fleshing out a character but have no mechanical crunch.
The other extreme is a few systems I've looked at which go into byzantine detail trying to support a simulation-focused approach, but they get so in depth that they slow down gameplay. Examples here would be something like Let's Talk! or Dokosoko Highschool, which are novel and admirable attempts to implement almost videogame, visual novel type relationship systems. Or even the Negotiation mechanics from Draw Steel which weren't designed for solo roleplaying, but can be MacGyver'd into something workable with some fiddling.
This very simple, pay-what-you-want system is an elegant balance between the two "archetypes" of design I've encountered in this space. I really believe that the best tools for solo roleplay need to spark imagination and contribute fodder for storytelling, but they also need to contribute to mechanical gameplay loops so that there's always a clear next step for the player to follow.
As an additional cherry on top, this tool can be used as a cherry on top- its very clean and minimal design being only 4 pages means that you can slap this on top of whatever other system you like with very little friction. If you want to combine it with other NPC generation systems for flavor or a more simulation-focused system or something like Universal NPC Emulator I think that you would be able to combine it with any other mechanics very easily and intuitively.
TLDR; super sick, super simple, A+ game design
