[Feature request] Randomize problem type parameters

[nisc]

It would be nice if the problem type could be randomized within set constraints.

E.g.:

• 1st choice: operators to be included (addition, subtraction, multiplication, division)
• 2nd choice (for each selected operator): min/max digits of 1st and 2nd number

(Offer some sensible defaults for low/mid/high difficulty levels.)

EDIT: This trainer here offers this, but doesn't look like it's open source.