If I chose to boot in recovery mode, the screen comes out garbled. Black mostly, with some white noise at the top (which I think is a console, mangled beyond recognition) and a purple rectangle to the left.
I installed Steam a few weeks ago, and it kept bothering me to add the ppa ubuntu-x-swat/x-updates,so I did it yesterday. After I installed it, my computer was fine until I rebooted. The computer wouldn't boot, it just froze on the splash screen of Elementary OS.
In the recovery mode, I did 'ppa-purge ubuntu-x-swat/x-updates', and then booted from the recovery mode, and it went fine.