A couple months ago something happened to the Portal 2 files on my computer and the game wouldn't launch. So instead of deleting the files or reinstalling Portal 2 I decided to ignore it. Today I decided to reinstall Portal 2 but there are a couple issues. One issue is this weird blue error sign I see when I try to start a new game. Another issue is that some walls are purple and the final issue is the portal gun doesn't appear when I tried to load a custom map.
What should I do? I really don't want to redownload Portal 2 since it's a eleven gigabyte download.