Retropie won't boot up - what happened?

[Grife]

So I got my GBZ up and running and I enjoyed an hour of Super Mario World, until I hit select+Y to save, and it froze, then I just powered it off. When I tried to restart, I got a bunch of errors after the Emulation Station screen (It was hard to read, but they were EXT4-fs errors, saying ext4_error_find_entry). I tried a while to get it to boot up until I eventually gave up and re-installed Retropie on the SD and it worked fine.

What happened? I can't find any info about the errors, and now I'm afraid to play any games because I know I could lose all of my progress again.

[HoolyHoo]

Turning off the gameboy without properly shutting down can corrupt your sd card. It appears that is what happened to you. Look for graceful shutdown mods in this forum. I believe @camble is selling a pcb to help you with this or you can make your own.