diff --git a/doc/abi.org b/doc/abi.org
new file mode 100644
index 0000000..aa89d0b
--- /dev/null
+++ b/doc/abi.org
@@ -0,0 +1,48 @@
+#+title: ABI
+
+largely based on the Guile Hoot's [[https://codeberg.org/spritely/hoot/src/branch/main/design/ABI.md][ABI]].
+
+* calling convention
+
+** non-tail calls
+
+- set the global variable ~$current-closure~ to the callee's closure.
+- load arguments into globals ~$arg0~, ~$arg1~, ~$arg2~, …
+- push return continuation onto ~$cont-stack~
+
+* scratchpad
+
+#+begin_src scheme
+  ;; Scheme source
+  (define (silly f g h x)
+    (f (h x) (g x)))
+
+
+  ;; continuation-passing style
+  (define (silly f g h x ktail)
+    (h x (κ (x0)
+            (g x (κ (x1)
+                    (f x0 x1 ktail))))))
+
+  ;; with explicit stacks
+  (define (silly)
+    (define f (pop!))
+    (define g (pop!))
+    (define h (pop!))
+    (define x (pop!))
+    (define ktail (pop-cont!))
+    (push-cont! (κ (x0)
+                   (define x* (pop!))
+                   (define g* (pop!))
+                   (push-cont! (κ (x1)
+                                  (define f* (pop!))
+                                  (define x0* (pop!))
+                                  (push-cont! ktail)
+                                  (push! x0*)
+                                  (push! x1)
+                                  (call! f)))
+                   (push! x*)
+                   (call! g)))
+    (push! x)
+    (call! h))
+#+end_src
diff --git a/doc/closure-conversion.org b/doc/closure-conversion.org
new file mode 100644
index 0000000..1f58588
--- /dev/null
+++ b/doc/closure-conversion.org
@@ -0,0 +1,83 @@
+#+title: closure-conversion
+
+the closure-conversion phase makes closed-over variables explicit by addition of the primitive ~make-closure~, taking a code pointer (in the CPS language, bare lambda) and the environment.
+
+* scratchpad
+
+#+begin_src scheme
+(letrec ((make-adder
+        (lambda (n)
+          (lambda (x)
+            (+ n x)))))
+((make-adder 3) 2))
+#+end_src
+
+#+begin_src scheme
+(define add-code
+  (lambda (n env)
+    (+ n (env-ref env 'x))))
+
+(define make-adder-code
+  (lambda (n)
+    (make-closure add-code ('x n))))
+
+(define make-adder (make-closure make-adder-code))
+
+(apply-closure (apply-closure make-addder 3) 2)
+#+end_src
+
+#+begin_src wat
+(module
+ (type $heap-object (sub (struct (field $hash (mut i32)))))
+ (type $closure (sub $heap-object
+                     (struct (field $hash (mut i32))
+                             (field $code (ref $cont-type)))))
+ (type $closure1 (sub $closure
+                      (struct (field $hash (mut i32))
+                              (field $code (ref $cont-type))
+                              (field $env0 (ref eq)))))
+ (global $arg0 (mut (ref null eq)) (ref.null eq))
+ (global $arg1 (mut (ref null eq)) (ref.null eq))
+ (global $arg2 (mut (ref null eq)) (ref.null eq))
+ (global $arg3 (mut (ref null eq)) (ref.null eq))
+ (global $arg4 (mut (ref null eq)) (ref.null eq))
+ (global $arg5 (mut (ref null eq)) (ref.null eq))
+ ;; ⋮
+ ;; (global $argn (mut (ref null eq)) (ref.null eq))
+
+ (global $current-closure (mut (ref null $closure)) (ref.null $closure))
+
+ (func $add-code (param $nargs i32)
+       (local $n (ref eq))
+       (local $x (ref eq))
+       (local.set $n (global.get $arg0))
+       (local.set $x (struct.get $closure1
+                                 (global.get $current-closure)
+                                 $env0))
+       (return (i32.add $n $x)))
+
+ (func $make-adder-code (param $nargs i32)
+       (local $n (ref eq))
+       (local.set $n (global.get $arg0))
+       (return (struct.new $closure1
+                           0
+                           $add-code)))
+
+ (func $main
+       (local.set $make-adder
+                  (struct.new $closure
+                              0
+                              $make-adder-code))
+       (global.set $current-closure $make-adder)
+       (global.set $arg0 (i32.const 3))
+       (local.set $f (call (struct.get $closure
+                                       $make-adder
+                                       $code)
+                           1))
+       (global.set $current-closure $f)
+       (global.set $arg0 (i32.const 2))
+       (return (call (struct.get $closure
+                                 $f
+                                 $code)
+                     1))))
+#+end_src
diff --git a/doc/notes.org b/doc/notes.org
new file mode 100644
index 0000000..910895c
--- /dev/null
+++ b/doc/notes.org
@@ -0,0 +1,53 @@
+#+title: assorted notes on compilation
+
+* letrec
+
+consider:
+
+#+begin_src scheme
+  (letrec ((even? (lambda (n)
+                    (if (zero? n)
+                        #t
+                        (odd? (- n 1)))))
+           (odd? (lambda (n)
+                   (if (zero? n)
+                       #f
+                       (even? (- n 1))))))
+    (even? 12))
+#+end_src
+
+#+RESULTS:
+: #t
+
+since ~letrec~ is a primitive construct in the CPS language, the translation of mutually recursive functions is straightforward:
+
+#+begin_src scheme
+  (define (-& x y k) (k (- x y)))
+  (define (zero?& x k) (k (zero? x)))
+  (define (halt x) x)
+
+  (letrec ((even? (lambda (n ktail)
+                    (zero?& n
+                            (lambda (x1)
+                              (if x1
+                                  #t
+                                  (-& n 1
+                                      (lambda (x2)
+                                        (odd? x2 ktail))))))))
+           (odd? (lambda (n ktail)
+                   (zero?& n
+                           (lambda (x1)
+                             (if x1
+                                 #f
+                                 (-& n 1
+                                     (lambda (x2)
+                                       (even? x2 ktail)))))))))
+    (even? 12 halt))
+#+end_src
+
+#+RESULTS:
+: #t
+
+however, Scheme permits ~letrec~-expressions with non-lambda right-hand sides, while the CPS language permits only kappa and lambda forms. thus, the handling of these forms is less trivial.
+
+for now we'll just reject any ~letrec~ forms with non-lambda right-hand sides, lol. they aren't very important.
diff --git a/golden/apply2/source.scm b/golden/apply2/source.scm
new file mode 100644
index 0000000..f1d25c6
--- /dev/null
+++ b/golden/apply2/source.scm
@@ -0,0 +1,5 @@
+((λ (f g x)
+   (f (g x)))
+ (λ (x) (+ x 4))
+ (λ (x) (* x 2))
+ 3)
diff --git a/golden/fn-of-fn/source.scm b/golden/fn-of-fn/source.scm
index 23de627..51e5d04 100644
--- a/golden/fn-of-fn/source.scm
+++ b/golden/fn-of-fn/source.scm
@@ -1 +1,3 @@
-(((λ (f) f) (λ (x) (* x 4))) 32)
+(((λ (f) f)
+  (λ (x) (* x 4)))
+ 32)
diff --git a/golden/let-fn/source.scm b/golden/let-fn/source.scm
new file mode 100644
index 0000000..6224cea
--- /dev/null
+++ b/golden/let-fn/source.scm
@@ -0,0 +1,2 @@
+(let ((square (λ (x) (* x x))))
+  (square 4))
diff --git a/src/Gyehoek/CPS/Convert.hs b/src/Gyehoek/CPS/Convert.hs
index 80232d0..11270dd 100644
--- a/src/Gyehoek/CPS/Convert.hs
+++ b/src/Gyehoek/CPS/Convert.hs
@@ -2,6 +2,7 @@
 {- HLINT ignore "Use camelCase" -}
 module Gyehoek.CPS.Convert
   ( convertProgram
+  , convertExp
   ) where
 
 import Gyehoek.CPS.Syntax
@@ -79,7 +80,6 @@ convert (Scm.ExpLet bs e) k =
         (continue #{kbody} ##{rhss'}))
     |]
 
-
 convert _ k = _
 
 convertProgram :: forall es. (GenSym :> es) => Scm.Program -> Eff es Program
@@ -88,3 +88,6 @@ convertProgram p =
     pure . Halt1 $ case NE.nonEmpty exps of
       Nothing -> ValLit Void
       Just es -> NE.last es
+
+convertExp :: forall es. (GenSym :> es) => Scm.Exp -> Eff es Exp
+convertExp e = convert e (pure . Halt1)
diff --git a/src/Gyehoek/CPS/Syntax.hs b/src/Gyehoek/CPS/Syntax.hs
index 419aa20..7840226 100644
--- a/src/Gyehoek/CPS/Syntax.hs
+++ b/src/Gyehoek/CPS/Syntax.hs
@@ -309,32 +309,53 @@ instance Vars Exp where
 
 
 data Scope
-  = Bind (List Name) Scope
-  | Use (List Name) Scope
-  | Leaf
+  = Bind (List Name) (List Scope)
+  | Use (List Name) (List Scope)
   deriving (Show, Eq)
 
 makeBaseFunctor ''Scope
 
-class Subst a where
-  substWith :: (Name -> Val) -> a -> a
-
-instance Subst Exp where
-  substWith sub = cata \e ->
-    _
-
 class Scoped a where
   scope :: a -> Scope
 
 instance Scoped Kappa where
   scope (MkKappa bs e) =
-    Bind bs (scope e)
+    Bind bs [scope e]
+
+instance Scoped Lambda where
+  scope (MkLambda bs k e) = Bind (bs ++ [k]) [scope e]
+
+instance Scoped Abs where
+  scope = \case
+    AbsKappa k -> scope k
+    AbsLambda l -> scope l
 
 instance Scoped Val where
   scope = \case
-    ValVar x -> Use [x] Leaf
-    _ -> Leaf
+    ValVar x -> Use [x] []
+    _ -> Use [] []
 
 instance Scoped Exp where
   scope = \case
-    ExpApply f xs k = _
+    ExpApply f xs k ->
+      Use (((f:xs) ^.. each . _ValVar) ++ [k]) []
+    ExpLetRec bs e ->
+      Bind (bs ^.. each . _1) $
+        (bs ^.. each . _2 . to scope)
+        ++ [scope e]
+    ExpPrim p k ->
+      Use (p ^.. each . _ValVar) [scope k]
+    ExpContinue k xs ->
+      Use (k : (xs ^.. each . _ValVar)) []
+    ExpIf c t f ->
+      Use (c ^.. _ValVar) [ scope t, scope f ]
+
+
+
+class Subst a where
+  substWith :: (Name -> Maybe Val) -> a -> a
+
+instance Subst Exp where
+  substWith f = go HS.empty where
+    go bound e = case scope e of
+      Use xs ss -> _
diff --git a/src/Gyehoek/Scheme/Syntax.hs b/src/Gyehoek/Scheme/Syntax.hs
index f173d46..e36b655 100644
--- a/src/Gyehoek/Scheme/Syntax.hs
+++ b/src/Gyehoek/Scheme/Syntax.hs
@@ -23,6 +23,8 @@ module Gyehoek.Scheme.Syntax
   , subst
   , getName
   , scm
+  , readExp
+  , readProgram
   )
   where
 
@@ -33,6 +35,7 @@ import Language.SexpGrammar
 import Language.SexpGrammar qualified as Sexp
 import Language.Sexp.Located qualified as S
 import Language.SexpGrammar.Generic
+import Effectful
 import GHC.Generics
 import Prelude hiding ((.), id)
 import Control.Category
@@ -49,6 +52,10 @@ import Data.HashSet (HashSet)
 import qualified Data.HashSet as HS
 import Data.Foldable (fold)
 import Language.Haskell.TH.Quote (QuasiQuoter)
+import Effectful.FileSystem (runFileSystem)
+import qualified Effectful.FileSystem.IO as FS
+import qualified Data.Text.Encoding as T
+import qualified Effectful.FileSystem.IO.ByteString as FB
 
 
 newtype Name = MkName { inner :: Text }
@@ -72,7 +79,8 @@ data Prim e
   | PrimWrite e
   | PrimZeroP e
   | PrimNewline
-  | PrimMakeClosure { code :: e, upvals :: List e }
+  | PrimMakeClosure { code :: e, env :: List e }
+  | PriEnvRef e Int
   deriving (Show, Generic, Functor, Foldable, Traversable, Data, Eq)
 
 instance Each (Prim e) (Prim e') e e'
@@ -157,6 +165,7 @@ primSexpIso namefn a = match
     $ With (. unop "zero?")
     $ With (. nullop "newline")
     $ With (. mkclosure)
+    $ With (. envref)
     $ End
     where
       idn s = el (sym (namefn s))
@@ -164,6 +173,7 @@ primSexpIso namefn a = match
       unop s = list $ idn s >>> el a
       binop s = list $ idn s >>> el a >>> el a
       mkclosure = list $ idn "make-closure" >>> el a >>> rest a
+      envref = list $ idn "env-ref" >>> el a >>> el Sexp.int
 
 instance SexpIso a => SexpIso (Prim a) where
   -- sexpIso = primSexpIso ("prim:"<>) sexpIso
@@ -259,3 +269,22 @@ subst f = \e -> cata go e mempty where
   go (ExpLetF _ _) _ = error "todo lol"
   go (ExpLambdaF bs e) bound = e $ insertFrom bs bound
   go e bound = embed $ fmap ($ bound) e
+
+
+
+fileName :: FilePath -> FilePath
+fileName "-" = "<interactive>"
+fileName e = e
+
+hGetContents :: FS.FileSystem :> es => FS.Handle -> Eff es Text
+hGetContents h = T.decodeUtf8 <$> FB.hGetContents h
+
+readProgram :: IOE :> es => FilePath -> Eff es Program
+readProgram fp = runFileSystem $
+  FS.withFile fp FS.ReadMode $ \h ->
+    Gyehoek.Sexp.parseSexps @CommandOrDef (fileName fp) <$> hGetContents h
+     >>= either error (pure . MkProgram)
+
+readExp :: IOE :> es => FilePath -> Eff es Program
+readExp fp = readProgram fp <&>
+  (^?! (#commandsAndDefs . _head . _Comm))
diff --git a/t.scm b/t.scm
index ac4a5ee..6b87d22 100644
--- a/t.scm
+++ b/t.scm
@@ -1,3 +1,21 @@
-(letrec ((x 3)
-         (y 4))
-  (values x y))
+(define (-& x y k) (k (- x y)))
+(define (zero?& x k) (k (zero? x)))
+(define (halt x) x)
+
+(letrec ((even? (lambda (n ktail)
+                  (zero?& n
+                          (lambda (x1)
+                            (if x1
+                                #t
+                                (-& n 1
+                                    (lambda (x2)
+                                      (odd? x2 ktail))))))))
+         (odd? (lambda (n ktail)
+                 (zero?& n
+                         (lambda (x1)
+                           (if x1
+                               #f
+                               (-& n 1
+                                   (lambda (x2)
+                                     (even? x2 ktail)))))))))
+  (even? 12 halt))