That's a very nice drawing Annie! I use a mouse too which is one of the reasons my fanarts take SO LONG to draw. I so wish I had a drawing tablet like most fanartists...
for using a mouse, that's a great job, It's almost impossible to use a mouse... And yeah The older rolly mice work way better for this stuff, but, It would be even cooler to have a touchscreen PC, or a drawing tablet thingy..
I use only a mouse on all of my digital work. but I can only do good with an older rollerball mouse. those stupid USB cable mice don't work as good, and the wireless laser mice suck terrible.