It'd be great for the game to come with a built-in calculator! I sometimes find myself scouring my house for a calculator just because i wanted to do some brain crunching mathematics.
Here's what it should look like. Has the same behaviour like the Performance Analyzer where it can be moved around
Just to add a bit more quality to the Quality-Of-Life, it could come with a history system where your recent calculations could be stored in.
Exit the calculator history by clicking the X button
I tried my best to mimic the design language of the game into the calculator so it'd would look as fitting as possible
Edit: it should also be pointed out that the calculator could be a scientific one. I just didn't have the time to make a complete one.