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A quick Google for murex cli -sea yields: https://murex.rocks and https://github.com/lmorg/murex, looks like a promising tool

It would be wonderful if this style of game had the option to render all the letters in lowercase, my brain just seems to treat different case symbols as representing different letters.

A possible consideration is older quiz/testing sites that pass along enough hints in HTML source code/CSS styling that identify correct answers prior to actually sending responses back for evaluation.