Box lighting effect
Cast a drop shadow across the element's box using a light source from a specified direction and distance.
This property expects six values: inset, offset-x, offset-y, blur-radius, spread-radius, and color. Only the offset-x, offset-y and blur-radius are required. Inset, spread-radius and color are optional.
inset keyword is specified as the first value, the shadow will be cast inside the element's border. If the
inset keyword is omitted, the shadow will be cast in its more typical way, outside the element's border.
Positive values for offset-x and offset-y define a light source above and to the left, casting a shadow below and to the right. Negative values have the opposite effect.
Larger blur-radius values create a wider and more diffuse light scatter.
Positive spread-radius values cause the shadow to lengthen. Negative spread-radius values cause the shadow to shrink.
More than one shadow may be specified by separating each group of six values with commas.