After beating the last screen at the end of the first level (the one with the wizards), my character runs to the right, and the screen get stuck there, the music still playing.
I can't bring up the menu or anything.

I reinstalled the game, the problem persists.

I have the same problem. I also recorded a video:
https://www.youtube.com/watch?v=ZJBSymDMZPU

The game is simply stuck at the end of level 1, won't go forward...
Cannot load level 2.

Computer specifications:
Windows 10 Pro (64-bit), 20H2, build 19042.868
Ryzen 1600
32 GB RAM
512 SATA SSD
Geforce GTX 1650, 4 GB GDDR5

What a joke, I wish I could hide games from the catalog so I don't have to see them anymore.

Is this bug fixed? Because the game is on sale right now.

Seems not, I've been playing some stuff I haven't tried for a while and forgot why I stopped playing this one.
It was because of this bug, no response and haven't seen any solutions offered.

I've got good news...

Some days ago (28 April 2021) I've got a response from the developers (Crunching Koalas) with the following information:

- - - - -

Sorry to hear you too are experiencing this bug. We just today found out what caused this issue. It's a problem of missing GOG client when some achievements are queued to be awarded.
We are fixing this nasty bug as we speak. Unfortunately patch will have go through certification process, so to save your and yours friend time i would suggest using GOG Galaxy client for now.
When the offline installer will be patched, i can remind you about it:) (ofcourse if you would like me to)

In the end there is nothing more painfull then games not working.
Thank you for your good intentions and sorry for the time wasted.
We will try to make this patch live as soon as we can.

- - - - -

So the version, that has problems is the "offline" version. If you use GOG Galaxy, there is no bug.
Hope, they will update it soon.

Wow, that sucks, but at least there is a fix in the pipeline, thanks for the update.

Unfortunately I can't even install Galaxy, but I will try again when the offline version is updated. And thanks for reaching out, I tend not to bother because I haven't had many positive experiences doing so. :P

Your welcome. The guys seemed very nice and they promised, the new version will be soon up on the GOG servers :)

New update, and yes I can finally play through to the rest of the game. Very good, enjoying the variety and even challenge, which I'm not usually thrilled by skill-based challenge but it's fun.
I'm only disappointed now that I'm not sure how/if I can edit my 1 star review, definitely doesn't deserve that anymore.

Yup, controls doesnt answer, it tells to use A key, and it does nothing.
Horrible game