At last here is the clue to Mondriaan's later paintings. It's Morse! Can't wait till the experts will publish the hidden messages.

The cryptogram-solver in me says

--- is O
. is E

and therefore in Morse Code it's

G O O G L E

(albeit with some adjustment for vertical spacing)

Yes, it ìs today's Google logo. Now what does this Mondriaan say, please?

See: Google-images-Broadway Boogie Woogie, if needs be..

'Broadway Boogie Woogie'

Inspired by his time in New York. No hidden messages in there.
Though someone has developed a computer programme to render 'Mondrian like' images

I was joking, olly. I hoped someone would come up with a good non-story. There is some confusion about the titles 'Broadway Boogie Woogie' and 'Victory Boogie Woogie' ( the latter was bought in 1998 by the Haags Gemeentemuseum for 80 million gulden appr. 40 million euro today. The aquisition was questioned in parlement.

Oops! cleaned out my picturehost files. Too much trouble to get them back in.See: Google-images-Mondriaan

Whoa, 40 million euro? Where did I put those paintbrushes?

The aquisition was questioned in parlement.

And the question was: What does it mean?
Answer: It is a 'Google Map' of Legoland.

They skipped that one. The question was, will most of the taxpayers be happy with it?

I think I got this all right...
igwqzdkcfgegf, eg ugd kcpt fluyxghlqjm?
EDIT: Please, don't anyone post the answer until the person it's addressed to has responded. Thanks!

mgllu, dqfpct, xzcm cm xzt wclmx xcjt qkk equ c'rf nttr qnrt xg kgo cr xg mtt ugdl ygmx !

drktmm c jqet q fktlcfqk tllyl - izcfz cm qkiqum ygmmcnkt - qfxdqkku, utm, c eg.

c nbche c ain cn!

By George, he's got it!

But I did make a clerical error, as I feared - the title of my post should have been "rtte ugd Qmp, not amp (since Q is the code for A), to keep the same substitutions Jackie used. Goofed again

(code available upon request, if for some strange reason it's wanted)

Yay! I first used just the first four letters of your name; but then I realized that there were so few repeat letters you might give up due it being too much bother; though I did think using the whole name would prolly make it too easy. No, I didn't need to ask! You're the first person I've ever made up a cryptogram for--it was harder that I thought it was going to be, for the reason you cited. It took me till the fourth proofreading to realize I'd left a letter out of your name!

Olly, I read yours as "i zjigt owz iz"...?

I saved the substitution I made up. It's
ABCDEFGHIJKLMNOPQRSTUVWXYZ
QOFETWHZCBPKJVGYALMXDRISUN

I found wofas code easier to crack as there were more double ups and single/Two letter words, I made some assumptions to fill out some words and then I worked out the offset. I love a good puzzle.

[blowing kiss e]

I'm impressed how anyone could crack that code. Never in my life would I have been able to patiently sort this one out. On my word of dbnl-x#.
So cheers Jackie and Olly. You are geniusses in the first degree.
( to me anyway ) How many codes have you Wofa? This one won't be much help any more at needs of topsecrecy.

That wasn't my code, that was Jackie's code, which I used to answer her coded message. Actulally I tried to make it easier to solve by using "giveaway" words in my message, like I've, I and a, all and see, and such like. And Jackie's name in the reply.

Making up a substitution code is easy: just write down the alphabet, as Jackie did, and write any rearrangement of the letters underneath it, random or selected (the code alphabet might be, for example,

plain: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
code: J A C K I E B D F G H Z Y X W V U T S R Q P O N M L

The problem in making your coded message, I've found, is keeping straight which set is the code letter and which is the plaintext letter when you finally write your message!