7.30.3 Can you answer these questions?

7.30.3.1 Realtime background blur

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=255414

Is it possible to have partially transparent cells (attached or docked) with live background blur? Something like this: 
 
Here's what I've tried: 
... 
[front-end] [cells] [style] [stylesheet] [blur]
 

asked by M.R. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=403 2 votes

7.30.3.2 What is the ComplexityFunction used by FullSimplify in Mathematica 12?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=255444

I was surprised to see  FullSimplify  make my expressions numerically unstable. The result can be summarized below: 
... 
[simplifying-expressions] [algebraic-manipulation]
                                                                                  

                                                                                  
 

asked by Yaroslav Bulatov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=217 2 votes

7.30.3.3 JordanDecomposition not evaluating

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=255344

When there are very small differences between entries in a diagonal matrix, sometimes  JordanDecomposition  does not evaluate and gives an error message: 
... 
[matrix] [numerics] [warning-messages]
 

asked by thorimur https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=63584 2 votes