Round 2 rated 16 runs a 3 and 84 a 2, which is too little spread to rank levels
by — but enough to ask what the 3s had in common. Contrast: 32.6 against 20.5,
a 59% gap and by far the largest of any feature. Rotation depth came second at
+1.2 turns. Board size and longest route ran the *other* way: the levels rated
harder were slightly smaller with shorter routes, which is what the design brief
has said all along — 难是难在用户无法一下子判断, not in how much board there is.
So within a depth, picking evenly across the ranked slice was diluting the one
thing the brief calls the point of the game. The depth quota already supplies
the difficulty range; inside a depth there is nothing to spread for, so it takes
the highest-contrast levels instead.
Taken alone that collapses the route grammars — two families filled 36 of the
50 — so the family cap comes down to 0.26. The pair beats the shipped round on
both axes rather than trading one for the other: contrast 14.8 / 22.0 / 27.9 →
15.2 / 24.9 / 28.6, families {18,12,8,2,10} → {13,13,5,9,10}. Same rule bot,
mechanics unchanged: worst blind streak still 1, dead taps still 0.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
