This is a little bit professional disorder (I am QA), so here are some ideas:
> Audio settings: simple sound indicator would be nice to illustrate how loud sound is while scrolling bar
> Credits. Centered infinite window with credits in center. Limitation of view with scroll bar would be better
> Game: Sound delay when sliding elements
> Room 2: Possible to slide \ bar at the point when water flows equally. Then room comes to passed/failed state with elements overlapping
> After finishing room could be shown which number it was. It's interesting to see how far you are
> In a room with orc and two blocks above cheering sounds before character goes to other side of the room and cheers
> After this room I got adds after every room. Little bit too much.
> Room with two doors. Red gem stays activated even if we drain water completely. Should it be like this?
> Room with orc over hole and lift for water. Spinner jumps a pixel