diff --git a/whalesong/world.rkt b/whalesong/world.rkt
index 734f317..85ccf23 100644
--- a/whalesong/world.rkt
+++ b/whalesong/world.rkt
@@ -1,7 +1,5 @@
 #lang s-exp "lang/base.rkt"
 
 (require "world/main.rkt")
-(require "world/types.rkt")
 
-(provide (all-from-out "world/main.rkt")
-         (all-from-out "world/types.rkt"))
+(provide (all-from-out "world/main.rkt"))
diff --git a/whalesong/world/impl.rkt b/whalesong/world/impl.rkt
new file mode 100644
index 0000000..dc28b67
--- /dev/null
+++ b/whalesong/world/impl.rkt
@@ -0,0 +1,27 @@
+#lang s-exp "../lang/js/js.rkt"
+
+(require "../image.rkt"
+         "types.rkt")
+
+(declare-implementation
+ #:racket "racket-impl.rkt"
+ #:javascript (
+               ;; the raw implementation doesn't know anything about
+               ;; Whalesong.
+               "raw-jsworld.js"  
+
+               ;; We add Whalesong-specific things here.
+               "kernel.js"
+               "js-impl.js"
+               )
+ #:provided-values (big-bang
+                    on-tick
+                    on-key
+                    on-release
+                    on-mouse
+                    key=?
+                    to-draw
+                    stop-when))
+
+
+
diff --git a/whalesong/world/main.rkt b/whalesong/world/main.rkt
index dc28b67..f02a5aa 100644
--- a/whalesong/world/main.rkt
+++ b/whalesong/world/main.rkt
@@ -1,27 +1,7 @@
-#lang s-exp "../lang/js/js.rkt"
+#lang s-exp "../lang/base.rkt"
 
-(require "../image.rkt"
+(require "impl.rkt"
          "types.rkt")
 
-(declare-implementation
- #:racket "racket-impl.rkt"
- #:javascript (
-               ;; the raw implementation doesn't know anything about
-               ;; Whalesong.
-               "raw-jsworld.js"  
-
-               ;; We add Whalesong-specific things here.
-               "kernel.js"
-               "js-impl.js"
-               )
- #:provided-values (big-bang
-                    on-tick
-                    on-key
-                    on-release
-                    on-mouse
-                    key=?
-                    to-draw
-                    stop-when))
-
-
-
+(provide (all-from-out "impl.rkt")
+         (all-from-out "types.rkt"))
diff --git a/whalesong/world/racket-impl.rkt b/whalesong/world/racket-impl.rkt
index 596b52f..dd1b00b 100644
--- a/whalesong/world/racket-impl.rkt
+++ b/whalesong/world/racket-impl.rkt
@@ -1,5 +1,7 @@
 #lang s-exp "../lang/base.rkt"
 
+(require "types.rkt")
+
 (provide big-bang
          to-draw
          on-tick