Password variation rules

I tryed numerous times to create a complex password for my Apple Id but failed . It indicates “ passwords do not match”.This is false because I write it down first then I type it in. Secndly, as I type each character I can see for a split second before it turns into a big dot, the actual leters, numbers, and commen characters. Once I typed a simple password with same number of digits, a password was created. I don’t like simple passwords. What are the password variation rules for creating an APPLE ID password? A plausible answer would be greatly appreciated.