I think the problem is that the art was scaled down for the game's target resolution and then scaled up to the actual display resolution which of course makes a mess of things. I'm not sure how easy this would be to do in Godot but it might be better to keep the art at its original resolution (or at least closer to it) and size it down at runtime.
A better explanation of the magic would help. It's definitely unintuitive in that it doesn't work the way you'd expect; I'm not sure about all playtesters but my natural inclination was to hold in a direction and then push the magic key.