Do not take the assessment without preparation. You should have a little time before you are required to complete it. Pilot Assessment Prep offers a pretty good product.
Shape Sudoku was a tough one. I've talked to several folks who took the assessment without preparation who were unsuccessful. If you have not begun the process of getting your logbook squared away and having your application reviewed, now is the time. You will have one shot at this, put in the effort (not that you weren't planning on it). Congratulations on getting the invite and best of luck.