"Pre-set" difficulty slider

[khlam]

I'd like to implement a 6-point pre-set difficulty slider that would automatically fills the addition/subtraction/multiplication/division lower and upper bounds with values according to the difficulty level.

I think it would be really cool if maybe the slider difficulty was something that follows the ISCED (https://en.wikipedia.org/wiki/International_Standard_Classification_of_Education)

So our goal here is to provide a quick way for anyone to practice their maths and maybe a way for someone to gauge where they currently are. So hypothetically if one thinks they can do mental-math at a very high level but they're struggling according to the slider difficulty, it provides a way for them to practice and work up towards their goals.