image_angle
Returns: Real
This value sets the angle (rotation) of the sprite and is
measured in degrees, with the right being 0º, up being 90º, left
being 180º and down being 270º. Set this variable to 0 to reset the
sprite to be drawn as was defined in the sprite editor. Please note
that for changes in this variable to be visible, the instance
should have either no draw event (and so GameMaker:
Studio will default draw the sprite) or be drawn using one of
the extended drawing functions like
draw_self() or
draw_sprite_ext().
image_angle = point_direction(x, y, mouse_x, mouse_y);
The above code will rotate the sprite of the instance to always point at the mouse position.