「Relative Difficulty」

Music Difficulty, Calculated by comparing accuracy of same player on different music

『Relative Level』

Performance of Player, Calculated from record performance
Highest record performance have greatest impact on the final result
*Record Performance: (accuracy - accuracy^2 + accuracy^4) * relative difficulty
*Impact on final result (higher to lower performance): 0.8, 0.8^2, 0.8^3 ...
*Same music with different platform: count only higher accuracy

Note, This is inaccurate, only a rough estimation based on the top 2000 players in each rank

Not included:
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