Implement Blinds performance calculation in osu!

[apollo-dw]

Pushing on with my quest for lazer mods in difficulty calculation, here's a blinds-related buff for osu!

The important talking points to consider are:

• As it stands, Blinds completely negates HD-based buffs. I think this is justified since the visual difficulty that Hidden provides becomes unimportant when the circles are never seen.
• Acc pp and Speed pp get a flat multiplier, whereas Aim gets one that is scaled by multiple factors (buffed by object count, nerfed by miss count & lower accuracy & higher HP drain rates)
• Yes, nerfed by higher HP drain rates. On a surface level, this seems contradictory, however it's important to note that the playfield is way more likely to be more revealed on higher drain rates.

The desmos link for the aim formula: https://www.desmos.com/calculator/vu1x6r0e4s
Some example values: https://hastebin.com/raw/lesufiyuga

Values were balanced with feedback from ppdev discord, in particular around C-TYPE [Bonsai's BasS-Type] +DT, since that's likely to be the most abusable ranked map with Blinds at the moment. -GN suggested a value of 750pp with BLDT, and I decided to balance around a little lower than that value just to stay on the safe side.

EDIT: After discussing values with MBMasher, I have buffed the effect of Blinds on aim pp. I've updated the links above with these changes.

[peppy]

How do you have one commit per line of change?

[bdach]

Hidden and Blinds are not actually incompatible in game (although maybe they should be?) but the way these bonuses are set up means that they are mutually exclusive. Was this intentional?

[apollo-dw]

Yeah, that's right. In the original comment I said I think it's justified since Blinds essentially displaces the visual difficulty of Hidden.

[MBmasher]

Yeah, this is good. Eventually we would look into making a difficulty skill for this (Visual+Memory skills?) however it scales fine as it is.