I'm playing on PC and for me the background images are stretched the same as AlexxxG reports for mobile.
Please add an option to turn off the music and ask players if they want a login or save local. I find it highly annoying that the game always opens my browser on startup..
The controls would be more intuitive if the marker wpould move with the tile i'm currently moving and not stay in place.
Other than that I like it so far, but I ran into a problem with Angel chapter 5 part 4. I'm quite sure I got it right but it won't complete. And when I go to the gellery after opening this picture it turns up as the puzzle. If I use "previous/next" the texts appear but the whole page is filled with the unsolved puzzle Angel 5-4.