Hey, i am going to buy an m3 simply and i was wondering, does the mp3 keep playing when the ds is closed? or do i have to keep the DS open? i will be using earphones.
I don't know for sure with the M3 Simply.
Since noone else has answered you though, I can tell you that with the M3 Lite (slot 2 cart) running Moonshell, playing MP3 or video you can shut the case and it will continue to play. I would assume the M3 Simply is the same.
Be aware the quality of MP3 sound isn't as good as it is on an iPod or other device. It is decent though and a reasonable trade off for having a DS rather than an iPod in your pocket.
Hope it helps!