A Mouse,ok.If you have Photoshop or Gimp,you can get rid of the curvy lines a bit.What I do when I draw something is that I draw it on paper first,then use a scanner or camera so I can use it on Gimp or Photoshop.Then I draw over the drawing on Gimp/Photoshop while it's zoomed in enough so that I don't make any curvy lines easily.It's suggested that you make a new layer before drawing over.
I think it's a little messy. You should clean it up a little like MasterC said and try to use some more detail. I recommend not using Paint to draw anything for feedback because it usually ends up looking sloppy. If you were to draw it first then scan it would look way better.