Full transparent header – how to ?

First of all, hello guys on wordpress.org 🙂

I have some questions about Pinboard theme which i use for running my website. I was fine with everythin i wanted to change on my website till today. Trying to make fully transparent header area (i made this full width before)

Here’s my website : http://lineage-eternal.pl/ (still under construction – just tryin implement on the website anything i want)

Here my #wrapper code

#wrapper {
	position:relative;
	max-width:1140px;
	margin:0 auto;
	box-shadow:0 0 18px rgba(0, 0, 0, .4);
	background:#f8f8f8;
	overflow:hidden;
}

When i replace background #f8f8f8 on transparent – whole site is gona transparent but shadow will stay. It can be deleted. Nevermind. Main problem focus on which code to change to make only header area transparent. Anyone has ideas ?

(sorry guys for my bad english, hope you understand what i mean)