diff --git a/index.html b/index.html
index 9fed43d..c54128c 100644
--- a/index.html
+++ b/index.html
@@ -31,7 +31,7 @@ <h1>
 
 <form>
 <textarea id="code">
-# Some code (with ignored arguments)
+# Ignored arguments
 false = \ _a b . b
 true = \ a _b . a
 not = \ b . b false true
@@ -43,16 +43,37 @@ <h1>
 # Invalid names
 %value = ()
 
-# Invalid args - unbound
-someFunc = \ local . true nonexistant local
+# Invalid whitespace (tabs)
+whitespace	=	()
 
-# Invalid args - scoped
-otherFunc = \ x . const (\ scopedArg . x ()) scopedArg x
+# Bare term
+(\ f x . f (x x))
+
+# Unbound
+some-func = \ local . true non-existent local
+
+# Out of scope args
+other-func = \ x . const (\ scoped-arg . x ()) scoped-arg x
+
+# Debug mode on
+#debug
+
+# Bare term - Debug
+(\ f x . f (x x))
+
+# Unbound - Debug
+some-func = \ local . true non-existent local
+
+# Out of scope args - Debug
+other-func = \ x . const (\ scoped-arg . x ()) scoped-arg x
+
+# Debug mode off
+#debug
 
 # More code
 zero = false
 succ = \ n f x . f (n f x)
-isZ = \ n . n (const false) true
+is-z = \ n . n (const false) true
 add = \ a b f x . a f (b f x)
 mul = \ a b f . a (b f)
 three = succ (succ (succ zero))
@@ -75,15 +96,15 @@ <h1>
 map = \ f xs . null xs nil (cons (f (head xs)) (map f (tail xs)))
 sum = foldr add zero
 drop = \ n . n tail
-take = \ n xs . isZ n nil (cons (head xs) (take (pred n) (tail xs)))
+take = \ n xs . is-z n nil (cons (head xs) (take (pred n) (tail xs)))
 col = \ n xs . head (drop n xs)
 colS = \ n xs . cons (col n xs) (cons (col (succ n) xs) (cons (col (succ (succ n)) xs) (nil)))
 row = \ n xs . map (col n) xs
-rowS = \ n xs . cons (row n xs) (cons (row (succ n) xs) (cons (row (succ (succ n)) xs) (nil)))
-chunk = \ a b xs . rowS a (colS b xs)
+row-s = \ n xs . cons (row n xs) (cons (row (succ n) xs) (cons (row (succ (succ n)) xs) (nil)))
+chunk = \ a b xs . row-s a (colS b xs)
 append = \ as bs . null as bs (cons (head as) (append (tail as) bs))
 concat = foldr append nil
-eq = \ a b . isZ a (isZ b) (isZ b false (eq (pred a) (pred b)))
+eq = \ a b . is-z a (is-z b) (is-z b false (eq (pred a) (pred b)))
 all = foldr (\ a b . a b false) true
 allf = \ f xs . all (map f xs)
 </textarea>
diff --git a/lambdacalc.js b/lambdacalc.js
index 6a349e3..09b7f05 100644
--- a/lambdacalc.js
+++ b/lambdacalc.js
@@ -6,7 +6,7 @@ CodeMirror.defineMode("lambdacalc", function(_config, modeConfig) {
   const BRACKETS = "bracket";
   const LAMBDA = "keyword";
   const DOT = LAMBDA;
-  const PREDEF = "variable";
+  const PREDEF = "text";
   const BOUND = "text";
   const ARGS = "def";
   const HOLE = "atom";
@@ -22,6 +22,11 @@ CodeMirror.defineMode("lambdacalc", function(_config, modeConfig) {
   const lamArg = /[a-zA-Z_][a-zA-Z0-9_\-']*|\./
   const numconst = /\d+/
 
+  function expectDefOrTerm(stream, state) {
+    return expectDef(stream, state)
+      || (state.debug ? null : expectTerm(stream, state));
+  }
+
   function expectDef(stream, state) {
     const name = (stream.match(defName)||[])[0];
     state.f = expectAssign;
@@ -61,6 +66,7 @@ CodeMirror.defineMode("lambdacalc", function(_config, modeConfig) {
       state.depth.pop();
       state.bound.pop();
     }
+    state.f = expectTerm;
     return BRACKETS;
   }
 
@@ -75,7 +81,7 @@ CodeMirror.defineMode("lambdacalc", function(_config, modeConfig) {
     if (!res) return null;
     if (state.bound.some(v=>v.includes(res))) return BOUND;
     if (state.defined.includes(res)) return PREDEF;
-    return UNDEF;
+    return state.debug ? UNDEF : "text";
   }
 
   function number(stream, state) {
@@ -102,30 +108,35 @@ CodeMirror.defineMode("lambdacalc", function(_config, modeConfig) {
 
   return {
     startState: function ()  { return {
-      f: expectDef,
+      f: expectDefOrTerm,
       depth: [],
       defined: [],
-      bound: [[]]
+      bound: [[]],
+      debug: false
     }; },
     copyState:  function (s) { return {
       f: s.f,
       depth: [...s.depth],
       defined: [...s.defined],
-      bound: s.bound.map(v=>[...v])
+      bound: s.bound.map(v=>[...v]),
+      debug: s.debug
     }; },
 
     token: function(stream, state) {
-      if (/\s/.test(stream.peek())) {
-        stream.eatSpace();
+      if (stream.eat(/\t/)) return FAIL;
+      if (/[ \n]/.test(stream.peek())) {
+        stream.eatWhile(/[ \n]/);
         return;
       }
       if (stream.peek() === '#') {
+        if (stream.match(/^#debug/))
+          state.debug = !state.debug;
         stream.skipToEnd();
         return "comment"
       }
       if (stream.sol() && state.depth.length === 0) {
         state.bound = [[]];
-        state.f = expectDef;
+        state.f = expectDefOrTerm;
       }
       return state.f(stream, state) || onFail(stream, state);
     },