I’m a minimal guy and as always while designing I was aiming for simplicity. Huge blurred background image to make everything pleasant to the eye and add dimension and on top of it a flat interface for superb legibility.
In order to keep interaction as clear as possible there’s live validation in all of the forms. Proper data input is signalised by little tick. Errors have their own animated tooltip with information and easily visible stroke. Also, based on this, the form keeps your eye movement to a vertical line to make filling and skimming as comfortable as possible. The data on the right is only additional information, for people that get confused somewhere in the way, instant help if you need it.
Filtering options stay hidden until you use the little arrow next to „Filtruj”. Then the separate, semi transparent block shows up giving you all you need to find anything you like.
Any colour you like
And, as everything sticks to pure css, why not give the user options to personalize the interface?