adjust gradient gen

core.rkt

@@ -113,7 +113,11 @@
   
   ; set up gradient options
   (define gradient-type (if radial "radial" "linear"))
-  (define gradient-direction (or direction (if horizontal "left" "top")))
+  (define gradient-direction
+    (format "~a~a" (if radial "circle at " "")
+            (if direction
+                (if horizontal "left" "top")
+                "center")))
   
   ; can't use standard make-css-strings in this case because the prefixes appear in the value,
   ; not in the property (which is always "background")