Photoshop suddenly changed?
Hey guys- I downloaded photoshop onto my computer on tuesday, and the layout was what I'm used to in photoshop. The dark gray background, everything in one window/tab. Up until around 4:00 this afternoon it still looked like that, but then as I was working on an animation, it started to get very slow, lagging, and not responding to my tablet. I tried to quit, but it froze, and I had to force restart my computer. I waited for about half an hour before coming back to it, then restarted my computer and tried to open the file I was working on before. I can no longer open it, as it says it is 'not a valid photoshop document'.
On top of that, the entire layout has changed. The color scheme is now white and pale gray, and the area where I would draw is now a separate window in a different tab that is not attached to the actual photoshop area. I have no idea now this happened, or why. Has anyone else experienced this, and if so, do you know how I can change it back, or at the very least why it occurred?
Image for reference:

I appreciate any help I could get, thank you.
