Add physical gates and finish floor switches.

game.scm

@@ -102,20 +102,59 @@
      (set! *snapshots* older-snapshots)
      (media-play audio:undo))))
 
+(define (sort lst <=)
+  (match lst
+    (() '())
+    ((_) lst)
+    ((pivot . rest)
+     (let lp ((left '()) (right '()) (pivot pivot) (rest rest))
+       (match rest
+         (() (append (sort left <=) (list pivot) (sort right <=)))
+         ((x . rest)
+          (if (<= x pivot)
+              (lp (append left (list x)) right pivot rest)
+              (lp left (append right (list x)) pivot rest))))))))
+
+(define (filter-map proc lst)
+  (let lp ((lst lst))
+    (match lst
+      (() '())
+      ((head . tail)
+       (let ((head* (proc head)))
+         (if head*
+             (cons head* (lp tail))
+             (lp tail)))))))
+
 (define (update-objects!)
   (set! *objects*
-        ;; TODO: Receive layer for sprite sorting
+        ;; Filter out the objects that are baked into the background
+        ;; and thus do not need to be rendered repeatedly.  Then,
+        ;; z-sort the list so we render in the correct order.
+        ;; Finally, convert positions to vec2s for more efficient
+        ;; rendering.
         (map (match-lambda
-               ((type #(x y) . properties)
-                `(,type ,(vec2 (* x tile-width) (* y tile-height)) ,@properties)))
-             ($ (level-actor *level*) 'describe))))
+               ((type #(x y _) . properties)
+                (pk 'obj `(,type ,(vec2 (* x tile-width) (* y tile-height)) ,@properties))))
+             (sort (filter-map (match-lambda
+                                 (((or 'wall 'exit) . _) #f)
+                                 (desc desc))
+                               ($ (level-actor *level*) 'describe))
+                   (lambda (a b)
+                     (match a
+                       ((_ #(_ _ az) . _)
+                        (match b
+                          ((_ #(_ _ bz) . _)
+                           (<= az bz))))))))))
+
+(define (collected-gem? idx)
+ (not (memq idx *gems*)))
 
 (define (load-level! idx)
   (set! *state* 'play)
   (set! *actormap* (make-whactormap))
   (clear-snapshots!)
   (with-goblins
-   (set! *level* ((vector-ref levels idx) (not (memq idx *gems*))))
+   (set! *level* ((vector-ref levels idx) (collected-gem? idx)))
    (update-objects!)))
 
 (define (next-level!)
@@ -172,6 +211,8 @@
           'next-level)
          (('gem)
           (media-play audio:pickup)
+          ;; TODO: Maybe show a little achievement popup when all gems
+          ;; are collected?
           (set! *gems* (cons *level-idx* *gems*))
           #f)
          (_ #f)))
@@ -239,16 +280,21 @@
 (define (draw-gem pos)
   (draw-tile context tileset 28 (vec2-x pos) (vec2-y pos)))
 
+(define (draw-gate pos open?)
+  (draw-tile context tileset (if open? 46 45) (vec2-x pos) (vec2-y pos)))
+
 (define (draw-object obj)
   (match obj
     (#f #f)
     (('player pos) (draw-player pos))
-    (('exit pos) (draw-exit pos))
-    (('wall pos type) (draw-wall type pos))
+    ;; Wall and exit tiles are baked into the background layer.
+    (('exit pos) #t)
+    (('wall pos type) #t)
     (('block pos type) (draw-block type pos))
     (('clock-emitter pos) (draw-clock-emitter pos))
     (('floor-switch pos on?) (draw-floor-switch pos on?))
-    (('gem pos) (draw-gem pos))))
+    (('gem pos) (draw-gem pos))
+    (('gate pos open?) (draw-gate pos open?))))
 
 (define (draw-background)
   (let* ((bv (level-background *level*))