Reimplement wireworld update; add stubs for new object types.

game.scm

@@ -127,18 +127,13 @@
 
 (define (update-objects!)
   (set! *objects*
-        ;; 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.
+        ;; z-sort the list so we render in the correct order.  Then
+        ;; convert tile positions to vec2s of pixel coordinates for
+        ;; more efficient rendering.
         (map (match-lambda
                ((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))
+                `(,type ,(vec2 (* x tile-width) (* y tile-height)) ,@properties)))
+             (sort ($ (level-actor *level*) 'describe)
                    (lambda (a b)
                      (match a
                        ((_ #(_ _ az) . _)
@@ -243,14 +238,9 @@
 (define (draw-exit pos)
   (draw-tile context tileset 27 (vec2-x pos) (vec2-y pos)))
 
-(define (draw-wall type pos)
+(define (draw-wall pos type)
   (let ((x (vec2-x pos))
         (y (vec2-y pos)))
-    (match type
-      ('brick
-       (draw-tile context tileset 22 x y))
-      (_
-       (draw-tile context tileset 2 x y)))
     (match type
       ('electron-head
        (draw-tile context tileset 4 x y))
@@ -258,7 +248,7 @@
        (draw-tile context tileset 5 x y))
       (_ #f))))
 
-(define (draw-block type pos)
+(define (draw-block pos type)
   (let ((x (vec2-x pos))
         (y (vec2-y pos)))
     (match type
@@ -287,11 +277,10 @@
   (match obj
     (#f #f)
     (('player pos) (draw-player 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))
+    (('exit pos) #t) ; drawn via background
+    (('wall pos type) (draw-wall pos type))
+    (('block pos type) (draw-block pos type))
+    (('clock-emitter pos) #t) ; drawn via background
     (('floor-switch pos on?) (draw-floor-switch pos on?))
     (('gem pos) (draw-gem pos))
     (('gate pos open?) (draw-gate pos open?))))