Alicornutopia

And, just because, here are the other four:

Yes: c, e, f
No: d

I’m sure you notice how this koan ratio is much greater than for the other strings. It turns out kuuskytkolme’s guesses might have given useful information in addition to entertainment.

4c
65
61
72
6e
20
48
78
64
63

All no

I didn’t realize when I made this rule quite how few strings were accepted.

Because of how few strings are accepted, I’ll give you a free one:

Yes: 98521

Possible properties:

All characters are in descending hex-digit order.
Never contains 3.
Never contains d.

Would people like me to continue what Unbitwise did of confirming superset/subset properties like this?

It makes it easier to make definite incremental progress. Whether that is a good thing for the game depends on how hard the rule is.

If you do:

I suggest that only explicit and valid Guesses should get such answers. I also think that saying subset/superset is best considered as syntactic sugar on "the master provides both a yes and a no counterexample to the guess, if possible".

02
20
03
30
04
40
05
50
06
60

Yes: 02
No: 03, 04, 05, 06, 20 (repeated), 30, 40, 50, 60

0a
a0
0b
b0
0c
c0
22
33
44
55