Ya, I really messed up and let Macbook get down to essentially no space left and now can't start. I've tried the safe start, while holding shift after starting but with no luck. The computer starts up fine and get the the sign in but makes it about 80% of the load bar and it shuts down/goes black. I was able to plug in external hard drive and hopefully save a compressed file from Macintosh HD, which I found online. Not quite sure what next step would be. Ideally could do safe start and delete some files and/or move over to external hard drive. But doesn't seem to be option. So believe next option might have to be to try and reboot from external hard drive, but not really sure how and couldn't find much on it. Thank you for help, really appreciate it!