well, if a beatmap provide hitcircle.png only (no hitcircleoverlay.png)
and your skin has hitcircleoverlay@2x.png
then hitcircleoverlay will be 2x ( and is a mess ) on sliders
(osu! public build)
hitcircle.png
hitcircleoverlay.png
hitcircleoverlay@2x.png
(this one is just a scaled-up @2x; crap quality x_x)
get this beatmap and test with default skin
(your osu! resolution must be 1600x or more)
edit: an inverse case (where beatmap has only hitcircleoverlay.png only) t/123489
and your skin has hitcircleoverlay@2x.png
then hitcircleoverlay will be 2x ( and is a mess ) on sliders
(osu! public build)
hitcircleoverlay.png
hitcircleoverlay@2x.png
(this one is just a scaled-up @2x; crap quality x_x)
get this beatmap and test with default skin
(your osu! resolution must be 1600x or more)
edit: an inverse case (where beatmap has only hitcircleoverlay.png only) t/123489