System files are on the fritz. What do I do?

[dolanspin]

Alright, so a half-hour ago, I found my Macbook Air running with a few hundred MB of space. After that, I uninstalled TF2 to get back about 23 GB.
About 2 minutes later, the System files had eaten all but about a hundred MB of space. This was so much that my browsers couldn't run. (I'm typing this on my phone)
I'd show a picture of the situation in System Information, but my computer auto-logged out and now it just shows a black screen, leading me to believe it doesn't have enough space to boot up.
So, is there any solution to this?
[doublepost=1535124135][/doublepost]

Alright, so a half-hour ago, I found my Macbook Air running with a few hundred MB of space. After that, I uninstalled TF2 to get back about 23 GB.
About 2 minutes later, the System files had eaten all but about a hundred MB of space. This was so much that my browsers couldn't run. (I'm typing this on my phone)
I'd show a picture of the situation in System Information, but my computer auto-logged out and now it just shows a black screen, leading me to believe it doesn't have enough space to boot up.
So, is there any solution to this?

UPDATE: I've managed to start it up.

 

[Fishrrman]

What happens if you try a "safe boot"?
(power down, then press the power on button and hold down the shift key).

 

[dolanspin]

Another update: It turns out all that space was being taken up by files in iMovie. My computer is freer now than it has been in months.

This is the system now!