diff --git a/game.scm b/game.scm
index 7b5672f..7710269 100644
--- a/game.scm
+++ b/game.scm
@@ -177,7 +177,7 @@
       (when (< i len)
         (let ((x (bytevector-ieee-single-native-ref bv i))
               (y (bytevector-ieee-single-native-ref bv (+ i 4)))
-              (idx (bytevector-s16-native-ref bv (+ i 8))))
+              (idx (bytevector-u16-native-ref bv (+ i 8))))
           (draw-tile context tileset idx x y)
           (lp (+ i 10)))))))
 
diff --git a/modules/game/actors.scm b/modules/game/actors.scm
index 4a7b3d9..1a9b370 100644
--- a/modules/game/actors.scm
+++ b/modules/game/actors.scm
@@ -1,5 +1,6 @@
 (define-module (game actors)
   #:use-module (goblins core)
+  #:use-module (hoot bytevectors)
   #:use-module (ice-9 match)
   #:export (^cell
             ^level))
@@ -67,7 +68,7 @@
     (('wire-state) #f)
     (('describe) '(player))))
 
-(define (^level bcom width height)
+(define (^level bcom width height objects)
   (define player (spawn ^player))
   (define player-coords (spawn ^cell))
   (define (make-grid)
@@ -176,9 +177,19 @@
   ;; TODO: actually write levels
   (warp-player 10 8)
 
-  ($ (grid-ref grid 3 7) (spawn ^exit))
+  ;; Parsed packed object data and spawn objects.
+  (let ((len (bytevector-length objects)))
+    (let lp ((i 0))
+      (when (< i len)
+        (let ((x (bytevector-u8-ref objects i))
+              (y (bytevector-u8-ref objects (+ i 1)))
+              (obj (match (bytevector-u8-ref objects (+ i 2))
+                     (1 (spawn ^wall 'brick))
+                     (id (error "invalid level object" id)))))
+          ($ (grid-ref grid x y) obj))
+        (lp (+ i 3)))))
 
-  ($ (grid-ref grid 4 4) (spawn ^wall 'brick))
+  ($ (grid-ref grid 3 7) (spawn ^exit))
 
   ($ (grid-ref grid 4 3) (spawn ^clock-emitter 3))
   ($ (grid-ref grid 5 3) (spawn ^wall 'copper))
diff --git a/modules/game/levels/level-1.tmx b/modules/game/levels/level-1.tmx
index 3564841..0022c58 100644
--- a/modules/game/levels/level-1.tmx
+++ b/modules/game/levels/level-1.tmx
@@ -3,21 +3,21 @@
  <tileset firstgid="1" source="tiles.tsx"/>
  <layer id="1" name="background" width="20" height="15">
   <data encoding="csv">
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,
-24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24
+23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,
+23,23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,23,23,
+23,23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,
+23,23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,23,
+23,23,23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,23,23,23,
+23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23
 </data>
  </layer>
 </map>
diff --git a/modules/game/levels/tiles.tsx b/modules/game/levels/tiles.tsx
index c0e26a3..2e52cd6 100644
--- a/modules/game/levels/tiles.tsx
+++ b/modules/game/levels/tiles.tsx
@@ -1,4 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <tileset version="1.8" tiledversion="1.8.6" name="tiles" tilewidth="16" tileheight="16" tilecount="300" columns="20">
  <image source="../../../assets/images/cirkoban.png" width="320" height="240"/>
+ <tile id="22">
+  <properties>
+   <property name="wall" type="bool" value="true"/>
+  </properties>
+ </tile>
 </tileset>
diff --git a/scripts/compile-map.scm b/scripts/compile-map.scm
index 2aee8be..7c83542 100644
--- a/scripts/compile-map.scm
+++ b/scripts/compile-map.scm
@@ -349,6 +349,11 @@ the default ORIENTATION value of 'orthogonal' is supported."
   (define (first-gid node)
     (attr node 'firstgid string->number))
   (define (parse-tileset node first-gid)
+    (define (parse-custom-tile node)
+      (let ((id (attr node 'id string->number))
+            (properties (map parse-property
+                             ((sxpath '(properties property)) node))))
+        `(,id . ((properties . ,properties)))))
     (let* ((name (attr node 'name))
            (tile-width (attr node 'tilewidth string->number))
            (tile-height (attr node 'tileheight string->number))
@@ -356,14 +361,15 @@ the default ORIENTATION value of 'orthogonal' is supported."
            (spacing (or (attr node 'spacing string->number) 0))
            (image (parse-image ((sxpath '(image)) node)))
            (properties (map parse-property
-                            ((sxpath '(properties property)) node))))
+                            ((sxpath '(properties property)) node)))
+           (custom-tiles (map parse-custom-tile ((sxpath '(tile)) node))))
       (make-tileset image tile-width tile-height
                     #:margin margin
                     #:spacing spacing
                     #:name name
                     #:first-gid first-gid
                     #:properties properties
-                    #:custom-tiles '())))
+                    #:custom-tiles custom-tiles)))
   (define (parse-external-tileset node)
     (let* ((first-gid (attr node 'firstgid string->number))
            (source (scope (attr node 'source)))
@@ -530,18 +536,26 @@ the default ORIENTATION value of 'orthogonal' is supported."
                                         (let ((bv (make-bytevector 10)))
                                           (bytevector-ieee-single-native-set! bv 0 (* x tw))
                                           (bytevector-ieee-single-native-set! bv 4 (* y th))
-                                          (bytevector-s16-native-set! bv 8 (tile-id (map-tile-ref tile)))
+                                          (bytevector-u16-native-set! bv 8 (tile-id (map-tile-ref tile)))
                                           bv))))
                                (iota (tile-layer-width layer))))
                  (iota (tile-layer-height layer))))))
 
-(define (compile-collision-layer layer)
-  (u8-list->bytevector
-   (append-map (lambda (y)
-                 (map (lambda (x)
-                        (if (tile-layer-ref layer x y) 1 0))
-                      (iota (tile-layer-width layer))))
-               (iota (tile-layer-height layer)))))
+(define (compile-walls tile-map layer-name)
+  (let ((tw (tile-map-tile-width tile-map))
+        (th (tile-map-tile-height tile-map))
+        (layer (tile-map-layer-ref tile-map layer-name)))
+    (u8-list->bytevector
+     (append-map (lambda (y)
+                   (concatenate
+                    (filter-map (lambda (x)
+                                  (match (tile-layer-ref layer x y)
+                                    (#f #f)
+                                    (tile
+                                     (and (assq-ref (tile-properties (map-tile-ref tile)) 'wall)
+                                          (list x y 1)))))
+                                (iota (tile-layer-width layer)))))
+                 (iota (tile-layer-height layer))))))
 
 (define (compile-object-layer tile-map layer)
   (let ((table (make-hash-table))
@@ -584,5 +598,6 @@ the default ORIENTATION value of 'orthogonal' is supported."
                    (values ,(compile-tile-layer tile-map "background")
                            (spawn ^level
                                   ,(tile-map-width tile-map)
-                                  ,(tile-map-height tile-map))))))))
+                                  ,(tile-map-height tile-map)
+                                  ,(compile-walls tile-map "background"))))))))
   (_ (error "file name expected")))