This was the update I was postponing for long time - UI update. Turns out that updating all of UI is not that simple, and involves many changes in other places. Who would have thought :). 
I liked majority of the layouts so they mostly stayed the same but all of UI got reskinned and polished. Some new effects are also in place. 

Next up: itch.io and Steam pages redo. As for updates - Control info/tutorial and controls rebinding. 

Changelog

- All UI elements now use a different color scheme
- More effects added to UI items (as hover effects etc.)
- More animations in menus
- Reworked statistics screen
- Added a load menu when clicking save slot
- Completely reworked pause screen together with new config options (which are of course saved)
- Puzzle selection screen improved a bit

Other changes
- Save slots are now 'unlimited'. Previously there could only be one save slot for each puzzle/piece count combination. Now you can create as many saves as you want
- Custom puzzles are now saved as high quality .jpg instead of .png, which reduces their size 
- Improved celebration after puzzle is completed
- Many other small tweaks and fixes