Capture the Flag (CTF) challenge 1

As You guys probably know, there are so-called "Capture the Flag" challenges. Specially prepared programs, images, documents, HTML pages, or sites contain a hidden message, called "flag". The message is hidden by simple but not that obvious means (no crypto keys breaking). So no JS, without bugs abuse, XML hacking - just plain Snap! (with libraries if told so).
If you discover the message, disclose only 2-3 new letters out of it to not destroy the fun (I hope) for others. After 24h I post the mega clue - the name of the well-known concept.

There is a challenge: :link:How empty is an empty project?:link:
The message has 27 letters (A..Z, underscore), starts with "CTF_".

First clue - use sparingly, if in danger of brain explosion ;)

Invisible to some degree.

I can't find it...

The first challenge failed :rofl:
The project is shared, so it should be visible. Updated first post to be more obvious...

Are the test blocks and the red stage relevant to the problem?

"test" blocks no. removed.

Ah. But the red stage is...

one hour later...
me: "I am not giving up. I WILL not give up. I WILL do this tomorrow."

you did a good! the only thing I found was the red stage.

do we have to code to do it?


The red "Untitled" costumes seem to be, unintended, "honey spot" to draw attention to irrelevant aspects. I'll remove it, but in real life, it's quite a useful concept.
Also, the message is slightly "volatile". Some project manipulations make it vanish.
It's best to start with the freshly loaded project.

Next clue: steganography, watermarking

Thank you cymplecy for help.

Where do I post what I think is the "flag"?

So, I'd pick out 3 consecutive letters that don't really give a clue to fellow Snappers

And maybe use

My 3 letters

this method as well


Uh, that's a nice idea!

Jens, Bernat and I wanted to build an escape room for quite a while now but got sidetracked by other work or babies :wink:

My 3 letters


:clap: Yes :clap:

Next clue: almost complete decoder
CTF_FLAG.sol script pic

How about "incomplete decoder"?
And what list do I put in there? And how was I supposed to figure out to use that decoder without that clue?

Its a puzzle :slight_smile:

The only thing left to work out is what list to supply the function

That's why he's given this to help :slight_smile:


He did this before the clue was given.

Well, Jadga (who is she BTW) is one of the Snap! team so has pretty good skills and managed to decode the hidden message without needing the clue.

Darek has given out this clue to help others who are not as experienced