Pretty simple, and as the title says, add in a menu option under Graphics that allows the user to scale the UI up or down from the default point. The change in size does not need to be big, call it ± 50% from the default. But it could accomplish one of 2 things:
Better fit/feel for users that don’t want each screen to fully occupy such a large percentage of the screen (i.e. character sheet being a little smaller would let you see what is going on with a targeted Hearthling easier).
Those with visual accessibility issues could scale up to better assist their accessibility and enjoyment of the game as a whole.
Might be a bit off, but for folks out there that are colorblind, this tweak could also include those types of accessibility options as well…again, just a thought.
I’m working on a full scale re-design of the in-game UI right now. One of the major changes is real estate taken by menus and where those menus are located. This is a general starting point and further iteration will happen as we figure out what works and doesn’t. I have mixed feeling about UI scaling vs. making an appropriately sized UI with proper relative spacing.
As for colorblind, feel free to comment here with the major pain points you have and I’ll make sure to look at them as we’re working towards an updated UI. Best possible scenario is that we create a UI that is accessible to colorblind folks (high enough contrast with clear separation and readability etc).
Personally I have no actual vision based pain points, but was thinking in terms of accessibility after having to have a meeting with our UX team at work and it got me thinking in those terms for the game. I cannot really speak for colorblind folks, so if anyone has such a requirement, feel free to chime in.
As for the scalability portion, even a revamp on the scale in general would be welcomed given the amount of real estate a menu and windows take up in my 24" monitor.
anyways, definitely love this idea, going to page 
