make custom entities override built-in entities

data/scenarios/Challenges/Ranching/pied-piper.yaml

@@ -164,7 +164,7 @@ entities:
       char: 'k'
     description:
       - Used by an `unlocker`{=entity} to open a a `locked door`{=entity}
-    properties: [known]
+    properties: [known, pickable]
   - name: unlocker
     display:
       char: 'u'
@@ -190,7 +190,7 @@ entities:
       attr: wood
     description:
       - wall
-    properties: [known, unwalkable]
+    properties: [known, unwalkable, boundary]
   - name: oats
     display:
       attr: oats

data/scenarios/Testing/00-ORDER.txt

@@ -70,3 +70,4 @@ Achievements
 231-requirements
 2085-toplevel-mask.yaml
 2086-structure-palette.yaml
+2239-custom-entity.yaml

data/scenarios/Testing/2239-custom-entity.yaml

@@ -0,0 +1,42 @@
+version: 1
+name: Custom entity
+description: |
+  Custom entity overriding standard entity
+creative: false
+objectives:
+  - goal:
+      - Move to (1,0)
+    condition: |
+      as base {
+        loc <- whereami;
+        return $ loc == (1,0)
+      };
+entities:
+  - name: rock
+    display:
+      char: '$'
+      attr: gold
+    description:
+      - Not your average rock!
+    properties: [pickable]
+    capabilities: [move]
+robots:
+  - name: base
+    dir: east
+    devices:
+      - logger
+      - grabber
+      - welder
+solution: |
+  grab;
+  equip "rock";
+  move
+known: [rock]
+world:
+  dsl: |
+    {grass}
+  palette:
+    'B': [grass, rock, base]
+  upperleft: [0, 0]
+  map: |
+    B

src/swarm-scenario/Swarm/Game/Entity.hs

@@ -436,7 +436,7 @@ data EntityMap = EntityMap
 instance Semigroup EntityMap where
   EntityMap n1 c1 d1 <> EntityMap n2 c2 d2 =
     EntityMap
-      (n1 <> n2)
+      (n2 <> n1)
       (c1 <> c2)
       (filter ((`M.notMember` n2) . view entityName) d1 <> d2)