Hi. I’m a new etterna player. (Rating around 17)
The game works flawlessly on my device, but I see strange stripe after playing a file.
These are examples.
Do they mean that my PC and/or keyboard are not suitable for etterna (or other games that require milliseconds accuracy)?
Could you give me an advice?
Thank you.
(I’m not a native speaker.)
This is typically an indication that the polling rate of your keyboard or related hardware is low. On higher polling rates, the scanlines are usually only visible when the bpm of the song is a certain factor of the polling rate. A low enough polling rate makes them always occur.
Polling rate issues aren’t always a serious concern other than being annoying and making your graph look like this. However, sometimes they can cause you to have forced inaccuracies in the most extreme situations.
Thanks for your advice! 
I will consider purchasing a keyboard with high polling rate
when I start playing for AAAs someday.
Yes, someday.
