Thanks for the feedback.
The inventory system can be a bit fiddly. You have to hover the cursor near the bottom center of the screen, then the inventory should pop up.
As for the mouse movement, it's best to drag the view around slowly. I might reduce the camera movement speed in a later version.. I'll probably be keeping the current joystick-like camera controls.
One place (or node) in the game's 3D environment is made up of 6 square images, all taken from different angles (every 90 degrees, front, right, top etc.) from a 3D scene rendered in Blender. These 6 images are configured to the faces of a cube to form a 360° panorama / 3D photo seen in the game. Not really that high-tech of a system :)