Thank you for playing and giving feedback! :)
Yes, its a bit linear, especially after the first level. I tried to give the player some exploration options on level 1, but time is just too limited in a 7 day jam to really make a huge maze. So I focused on polishing what I have and concentrate on the story and general completeness. There are no invisible walls (wanted to do that, but the time...), but there is one 1 hidden secret switch-door though. :D