TL;DR - Too Long; Didn't Read

Provides Shortcode for easy assigning a TL;DR section

Put the Shortcode [tldr] or [tl_dr] around an abstract written on the end of the post. You're done.

[tldr]
This is an abstract
[/tldr]

Install Plugin via WordPress Install or upload the .zip file

nope.

Of course you can!

Using your own styles: Create a CSS file named 'screen_custom.css' in the 'css/' folder of the plugin. This will be taken as style file instead.

Alternatively you can overwrite single properties with your default stylesheet:

.tldr-section /* The Wrapper for the .tldr-list */ 
.tldr-list /* UL which holds one LI with a link to the TL;DR-Section */ 
.tldr-link /* The link to the bottom, contains a span with a arrow pointing down */
.tldr /* DIV-Wrapper for the TL;DR section, usually bold text */
.tldr-text /* SPAN-Wrapper for the "TL;DR:" line before the text */