Thanks for the feedback. I am working on an update for the camera movement. The current implementation was designed for either keyboard only, or gamepad. But since the game forces you to close a menu with the mouse to start playing, naturally you will think you have to keep moving the mouse, which is where confusion begins.
The updated controls will feel much more natural for a keyboard+mouse combo. However I will probably give the option to switch back to the previous method in the menu, since it's also nice to not have to control with the mouse.