General Guidelinethis guideline is useless.
Use the same slider tick rate on every difficulty as it is a property of the music rather than the mapping. However, lower difficulties may use lower tick rates to reduce accuracy requirements for newer players, providing they still follow the rhythm of the song. Using high tick rates purely to increase score/combo/difficulty is senseless.
It's very common to set tick rate based on what aesthetic you want, or in some cases increase slider tick rate to either 3, 4, or 8 to get desired patterns, which has been commonly accepted.
It doesn't even help new mappers, no reason to keep it.
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Rain RuleIf I had chosen to use hyperdashes during the rain on chouon chuu haikatsuryou test rain, I would have been limited to a maximum 2 hyperdashes in a 40 second period which is dumb.
Basic-snapped hyperdashes must not be used more than two times within a slider. The slider path must be simple and easy-to-follow.
2 times in a row seems quite reasonable to enforce and makes more sense.
Either apply that, or move the existing rule to the guidelines in it's current format.