Generate an image  of a squirrel  going up a  tree, set  against a warm , sunny afternoon  backdrop with a  subtle gradient of  autumnal colors , featuring a  majestic oak tree  with gnar led branches and  a rough,  moss-covered trunk , where the  squirrel, with  its fluffy grey  and brown fur , is captured  in mid-cl imb, its  tiny paws  grasping a  branch, and  its bright,  inquisitive  eyes looking upwards , conveying a  sense of determination  and agility,  with a shallow  depth of field  to emphasize the  squirrel's movement  and the texture  of the tree  bark.