Steam Account Making

Okay, here's the story:

Went to the MCM London Expo last week, and got Metro 2033 free on Steam (as a code)
Tried to make an account on Steam, but it keeps telling me that my password is unacceptable. Can someone help out with the specifications for steam passwords?

I think mine just includes numbers, capital letters and lowercase letters :)

I find this combination of words work amazingly:

[Colour with a capital letter][FULLSTOP][Item with a capital letter][Random 2-3 digits]

E.g

Red.Brick98

Habbox.Forum10

Orange.Town57

Put passwords like that into https://howsecureismypassword.net/ and be surprised at how such a simple password to remember is so secure. Will work in Steam easily.

Adding an extra digit to the end encrypts it even further, and so on and so forth.