I had this problem yesterday, and it persists today. All of the windows (notebook, IDE, simulation, and shell) are compressed at the top of the screen.
Reloading the page doesn’t help, nor does choosing a different layout from the 4 option at the bottom (although that does seem to alter the scrunched-up windows at the top). I’m on Chrome (Version 86.0.4240.193) on Windows 10. I’ve cleared the cache on Chrome. I’ve even restarted the computer (as part of a Win10 update - my problem started before the update to be clear).
Everything worked fine last week, when last I logged in.