(cond (c (clear-zone-interior (field-zone f) c))
 (t (clear-zone-interior (field-zone f)¬
W-BACKGROUND))))
 ((eq b 'pattern); patterned background
 (cond (c (pattern-zone-interior (field-zone f)¬
c))
 (t (pattern-zone-interior (field-zone f)¬
W-PATTERN-1))))
 ))); no background at all!

 (defun draw-field-background (f); just what it¬
says
 (let ((b (get (field-properties f)¬
'empty-ground)) ; check if has one
 (c (get (field-properties f) 'empty-colour)))
 (cond ((eq b 'solid); solid background
 (cond (c (clear-zone (field-zone f) c))
 (t (clear-zone (field-zone f) W-BACKGROUND))))
 ((eq b 'pattern); patterned background
 (cond (c (pattern-zone (field-zone f) c))
 (t (pattern-zone (field-zone f) W-PATTERN-1))))
 ))); no background at all!

 (defun draw-field-border (f); draw outline, if¬
any
 (let ((c (get (field-properties f)¬
'border-colour)))