Fix bug where gem could be marked as collected even if move was undone.

game.scm

@@ -196,6 +196,10 @@
 (define (next-level!)
   (let ((idx (+ *level-idx* 1)))
     (pk 'next-level idx)
+    ;; TODO: Maybe show a little achievement popup when all gems
+    ;; are collected?
+    (when (with-goblins ($ (level-actor *level*) 'gem-collected?))
+      (set! *gems* (cons *level-idx* *gems*)))
     (set! *level-idx* idx)
     (if (< idx (vector-length levels))
         (begin
@@ -272,10 +276,7 @@
                 (('player-death x y)
                  (play-sound-effect audio:die))
                 (('pickup x y)
-                 (play-sound-effect audio:pickup)
-                 ;; TODO: Maybe show a little achievement popup when all gems
-                 ;; are collected?
-                 (set! *gems* (cons *level-idx* *gems*)))
+                 (play-sound-effect audio:pickup))
                 (('emit x y)
                  (play-sound-effect audio:emit))
                 (('emitter-on x y)

modules/game/actors.scm

@@ -396,6 +396,7 @@
     (('wire-state grid-info from from-x from-y) #f)
     (('update-wire-state grid-info neighbor-grid) #f)
     (('alive?) (not ($ picked-up?)))
+    (('previously-collected?) previously-collected?)
     (('describe)
      (if previously-collected?
          `(ghost-gem ,position)
@@ -758,6 +759,7 @@
   (define player (spawn ^cell))
   (define objects (spawn ^cell '()))
   (define event-log (spawn ^event-log))
+  (define gem-collected? (spawn ^cell))
 
   ;; Spatial partition
   (define (for-each-coord proc)
@@ -874,8 +876,14 @@
                 (cons obj (lp rest))
                 (match ($ obj 'position)
                   (#(x y z)
+                   ;; Remove from spatial partition.
                    (let ((cell (grid-ref grid x y)))
                      ($ cell (delq obj ($ cell))))
+                   ;; If this is a gem, then set a flag that the
+                   ;; player has collected it.
+                   (when (and (eq? ($ obj 'type) 'gem)
+                              (not ($ obj 'previously-collected?)))
+                     ($ gem-collected? #t))
                    (lp rest)))))))))
   (define (tick-object obj)
     (let ((prev-pos ($ obj 'position)))
@@ -914,4 +922,5 @@
         (let ((cell (grid-ref grid x y)))
           ($ cell (cons obj ($ cell)))))))
     (('flush-events)
-     ($ event-log 'flush))))
+     ($ event-log 'flush))
+    (('gem-collected?) ($ gem-collected?))))