The top button mouse cover was an easy surface to create; I used a constraint curve to make sure the shape was equal and not flat. I used the surface fill tool and the blue line shown before as the boundary, and the constraint curve to ensure that it was equal throughout the entire surface. I then cut the curve in half using the plane i sketched the constraint curve on.

I then had to model the finger troughs, I made an inverted curve which i mirrored to make the troughs even and then surface filled the surface again. The last step for modelling was the trough where the mouse roller goes. I made a plane on top of the mouse, and while looking at the top view of the picture i traced one half of the trough where the mouse wheel goes and mirrored it, for equal curvature, i then trimmed the surface creating a hole in the mouse. Finally made another inverted constraint curve for the convex surface; which i then surface filled with the constraint curve which finished the surface of the mouse.

finished mouse: