New Password Idea: Word-walker I thought of a new way to generate my passwords, and even though it's probably not very clever in the long run, it could still make for a fun code-golf.

Taking a string of words, the password is generated thus:


Pick the nth character in the nth word
If n is larger than the word, continue counting backwards


Example:

This is a fun task!
T     s a  u      !


T is the first character
s is the second
a is the first, but going back and forth it is also the third
u is the second but because of counting backwards it's also the fourth
'!' is the fifth character in 'task!' and thus will be included in the final password, Tsau!

Rules


Input will be a string
Separate the string on spaces, all other characters must be included
Uppercase letters must remain uppercase, same with lowercase
You take n steps in each word, where n is the number of words that have come before plus one
If n is larger than the word, you must step backwards through the word, if you hit the start, you go forward again until you have stepped n times
The first and last character is only stepped once, so 'fun' on the seventh position as an example goes 'funufun' and ends on n, not 'funnuff' and ends on f
Output must be a string


Examples:

Input              Output
Once Upon A Time   OpAe
There was a man    Taaa
Who made a task    Waak
That was neat!     Taa
This is a long string to display how the generator is supposed to work  Tsagnoyotoipto


The shortest code in bytes wins!
Python 2, 72 bytes



lambda s:''.join((-~i*(w+w[-2:0:-1]))[i]for i,w in enumerate(s.split()))


Try it online!