Exciting news! and what is business casual?? help!

I heard back about the job at the Casino! I am scheduled to go in Friday morning for an assessment test. I asked what that was and the HR lady said I don't know, it's done through a third party vender so we don't see what it is. She said she will take my purse and my cell phone, put me in a room with a computer and I can't come out until I finish the test which usually takes around an hour...She said I think it tests your logic and critical thinking but I don't think there is any math (gosh I hope not because I suck at math!) She told me that is all I will be doing on Friday, but I should still dress business casual...so I have no idea what to wear...this will be the first time they will be actually seeing me, and I want to make a good impression...I want to look confident but also look like I can connect with VIP's from large companies as that will be part of my job. Any suggestions? On day 4 today of the pouch test and my hunger is in control and small portions are filling me up again! Woo Hoo!