Slotcore and Freedom Dive [Four Dimensions]. The death-stream compilation is just hard because it's really long and you end up getting tired, if you just do a little pause between each song you can super easily clear it.
Slotcore is impossible because wtf jumps 270 BPM, 1/2 1/2 1/4 1/4 1/4 1/4 1/4 1/2 1/4 1/4 1/4 1/4 1/4 /14 etc, and the other one because of super exhausting map + long spacing, making it an instant fail if you move your cursor just a little wrong.
Chipscape hardest thing is, imo, those super short sliders.
