clean up stylesheet
clean up stylesheet

Made the less code briefer and cleaner. Also substituted a global
variable usage.

notbakaneko/osu-web,notbakaneko/osu-web,notbakaneko/osu-web,nanaya/osu-web,LiquidPL/osu-web,LiquidPL/osu-web,LiquidPL/osu-web,ppy/osu-web,notbakaneko/osu-web,nanaya/osu-web,LiquidPL/osu-web,LiquidPL/osu-web,nanaya/osu-web,nanaya/osu-web,ppy/osu-web,notbakaneko/osu-web,ppy/osu-web,ppy/osu-web,ppy/osu-web,nanaya/osu-web