You will see three or four natural magic books at the bottom (you have bought them and pulled them to the bottom)

The most important thing can only be done in the mall.

Pull back the top cen and click it gently (just see that the cursor on the top cen is lit (don't really click, just redo it). After clicking, the top cen still touches the screen, and then clicking Buy still makes the cursor.

Move there and still let the pen touch the screen. ) The penultimate magic book will find the upgrade package.