Negative Balance popup is hard to see and is over balance

[dkohlbre]

Ideally, the "You have a negative balance!" popup should be:

• Large
• Red
• not covering how much you owe!

I'd suggest something like, if >$5 owed, have a large popup covering the left side of the screen (so that you can still see items being scanned) that goes away after like 5 seconds or something.