more levels

app/Model.hs

@@ -85,20 +85,21 @@ isWall world (Location n y x) =
 type Movement = (Int, Int)
 
 moveBlock ::
-  World ->
-  Map Location (Char, Box) ->
-  Map Location (Int, Char, Maybe Location) ->
-  Location ->
-  Movement ->
+  World {- ^ world -} ->
+  Map Location (Char, Box) {- ^ location cache -} ->
+  Map Location (Int, Char, Maybe Location) {- ^ accumulated changes -} ->
+  Location {- ^ source location -} ->
+  Movement {- ^ movement direction -} ->
   Rational {- ^ offset -} ->
   Maybe (Map Char (Maybe Location))
 
--- moving into a wall, not possible
+-- moving a wall, not possible
 moveBlock world _ _ loc _ _
   | isWall world loc = Nothing
 
 -- move introduced a loop, trim off the tail and report success
 moveBlock _ _ visited loc _ _
+  -- XXX: ensure update is consistent to support flipped levels
   | Just (n,_,_) <- Map.lookup loc visited
   = Just (Map.fromList [(c,l) | (a,c,l) <- Map.elems visited, a >= n])
 
@@ -126,7 +127,7 @@ moveBlock' ::
     Movement ->
     Char ->
     Box ->
-    Set Location ->
+    Set Char ->
     Rational {- ^ offset -} ->
     Maybe (Map Char (Maybe Location))
 moveBlock' world locMap visited loc loc' dir name box enters offset =
@@ -138,16 +139,16 @@ moveBlock' world locMap visited loc loc' dir name box enters offset =
         moveInto =
          do (n,b) <- Map.lookup loc' locMap
             (locI, offset') <- enterLoc world n b dir offset
-            if Set.member locI enters then
-             do epsilon <- findEpsilon world (locName locI)
+            if Set.member (locName loc') enters then
+             do epsilon <- findEpsilon world (locName loc')
                 moveEpsilon epsilon
             else
-              moveBlock' world locMap visited loc locI dir name box (Set.insert locI enters) offset'
+              moveBlock' world locMap visited loc locI dir name box (Set.insert (locName loc') enters) offset'
 
         moveEpsilon epsilon =
          do let eBox = boxIx world epsilon
             (locI, offset') <- enterLoc world epsilon eBox dir offset
-            moveBlock' world locMap visited loc locI dir name box (Set.insert locI enters) offset'
+            moveBlock' world locMap visited loc locI dir name box enters offset'
 
         moveToEat =
          do let dir' = invert dir