Index: day15.rkt
==================================================================
--- day15.rkt
+++ day15.rkt
@@ -101,22 +101,21 @@
 ;; Is point p inside grid g? Film at 11
 (define (inside-grid? g p)
   (match-define (posn px py) p)
   (and (>= px 0)
        (>= py 0)
-       (< px (grid-rows g))
-       (< py (grid-cols g))))
+       (< px (grid-cols g))
+       (< py (grid-rows g))))
 
 ;; Get a list of a positions neighboring points, ensuring none are out of bounds
 (define (neighbor-coords g pos)
   (match-define (posn x y) pos)
   (filter (curry inside-grid? g)
-          (map (lambda (lst) (apply posn lst))
-               `((,(- x 1) ,y)
-                 (,x ,(+ y 1))
-                 (,(+ x 1) ,y)
-                 (,x ,(- y 1))))))
+          (list (posn (- x 1) y)
+                (posn x (+ y 1))
+                (posn (+ x 1) y)
+                (posn x (- y 1)))))
 
 ;; Get all the EMPTY neighboring points of a given spot OR list of spots.
 ;; If a (listof posn?) is passed, ensures the returned list does not include
 ;; any of the original positions.
 (define (free-neighbors-at world pos)