Edit2: fixed with version 1.11

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I'm on Linux Mint and so far everything worked just fine, just when clicking for leaving the game nothing at all happened.
So I tried different alternative approaches (key combinations for quitting the current program, Alt-Tab, switching to a different desktop, opening the system monitor) nothing worked so I had to use the reset function.

Not so keen on doing that again.

Edit: Did actually try it again, same outcome.

Same here on my System (Debian Stretch). However, leaving the game is not a big deal with my window manager, since even in "fullscreen" mode, I can move the window around and then hit the close button.

As a workaround for others: it might help to set the game to windowed mode in the video settings, so that you could reach the standard close button.

Unfortunately I'm now so far to call the Linux version of this game totally broken.

After finishing this first area, you will see a black screen instead of a video sequence (although that's not exactly better under Windows7 too) and then in the scene afterwards I couldn't interact with anything which made it impossible for me to continue at all.

I can confirm those problems on my Debian stretch, too. Exiting the game using ALT+F4 works though.

Minor issue: Typo in the german version in the first screen: "Wekzeugkasten"

In disabling fullscreen mode in the game settings I have also found a solution to the fact that my key combinations are not working when the game is running. In windowed mode I can now simply close the game with Alt-F4 (or tab out of the game etc., everything works) too. Even better I make it fullscreen again with means of Linux Mint by pressing Super+F, I only have to press that after every start of the game.

Unfortunately the video playback issue still ruins the game, and switching to Windows7 doesn't make it any better as there is a similar issue with the video playback.