diff --git a/beautiful-racket/br/demo/hdl/DMux.hdl b/beautiful-racket/br/demo/hdl/DMux.hdl
new file mode 100644
index 0000000..328c556
--- /dev/null
+++ b/beautiful-racket/br/demo/hdl/DMux.hdl
@@ -0,0 +1,20 @@
+#lang br/demo/hdl
+
+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/01/DMux.hdl
+
+/**
+ * Demultiplexor:
+ * {a, b} = {in, 0} if sel == 0
+ *          {0, in} if sel == 1
+ */
+
+CHIP DMux {
+    IN in, sel;
+    OUT a, b;
+
+    PARTS:
+    Not
+}
diff --git a/beautiful-racket/br/demo/hdl/Dmux.tst.rkt b/beautiful-racket/br/demo/hdl/Dmux.tst.rkt
new file mode 100644
index 0000000..efaf4bd
--- /dev/null
+++ b/beautiful-racket/br/demo/hdl/Dmux.tst.rkt
@@ -0,0 +1,30 @@
+#lang br/demo/hdl/tst
+
+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/01/DMux.tst
+
+load DMux.hdl,
+// output-file DMux.out,
+// compare-to DMux.cmp,
+// output-list in%B3.1.3 sel%B3.1.3 a%B3.1.3 b%B3.1.3;
+output-list in, sel, a, b;
+
+set in 0,
+set sel 0,
+eval,
+output;
+
+set sel 1,
+eval,
+output;
+
+set in 1,
+set sel 0,
+eval,
+output;
+
+set sel 1,
+eval,
+output;
diff --git a/beautiful-racket/br/demo/hdl/Mux.hdl b/beautiful-racket/br/demo/hdl/Mux.hdl
new file mode 100644
index 0000000..57fe089
--- /dev/null
+++ b/beautiful-racket/br/demo/hdl/Mux.hdl
@@ -0,0 +1,23 @@
+#lang br/demo/hdl
+
+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/01/Mux.hdl
+
+/** 
+ * Multiplexor:
+ * out = a if sel == 0
+ *       b otherwise
+ */
+
+CHIP Mux {
+    IN a, b, sel;
+    OUT out;
+
+    PARTS:
+    // Put your code here:
+    Not(in=sel, out=sel-opposite);
+    And(a=a, b=sel-opposite, out=maybe-a);
+    Or(a=maybe-a, b=b, out=out);
+}
diff --git a/beautiful-racket/br/demo/hdl/Mux.tst.rkt b/beautiful-racket/br/demo/hdl/Mux.tst.rkt
new file mode 100644
index 0000000..0f20c9c
--- /dev/null
+++ b/beautiful-racket/br/demo/hdl/Mux.tst.rkt
@@ -0,0 +1,51 @@
+#lang br/demo/hdl/tst
+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/01/Mux.tst
+
+load Mux.hdl,
+// output-file Mux.out,
+// compare-to Mux.cmp,
+// output-list a%B3.1.3 b%B3.1.3 sel%B3.1.3 out%B3.1.3;
+output-list a, b, sel, out;
+
+set a 0,
+set b 0,
+set sel 0,
+eval,
+output;
+
+set sel 1,
+eval,
+output;
+
+set a 0,
+set b 1,
+set sel 0,
+eval,
+output;
+
+set sel 1,
+eval,
+output;
+
+set a 1,
+set b 0,
+set sel 0,
+eval,
+output;
+
+set sel 1,
+eval,
+output;
+
+set a 1,
+set b 1,
+set sel 0,
+eval,
+output;
+
+set sel 1,
+eval,
+output;
diff --git a/beautiful-racket/br/demo/hdl/info.rkt b/beautiful-racket/br/demo/hdl/info.rkt
new file mode 100644
index 0000000..e3d24be
--- /dev/null
+++ b/beautiful-racket/br/demo/hdl/info.rkt
@@ -0,0 +1,3 @@
+#lang info
+
+(define module-suffixes '(#"hdl" #"tst" #"cmp"))
\ No newline at end of file
diff --git a/beautiful-racket/br/demo/hdl/tokenizer.rkt b/beautiful-racket/br/demo/hdl/tokenizer.rkt
index 44e644b..9c4a490 100644
--- a/beautiful-racket/br/demo/hdl/tokenizer.rkt
+++ b/beautiful-racket/br/demo/hdl/tokenizer.rkt
@@ -9,7 +9,9 @@
     (define get-token
       (lexer
        [(eof) eof]
-       [(seq "/*" (complement (seq any-string "*/" any-string)) "*/")
+       [(union
+         (seq "/*" (complement (seq any-string "*/" any-string)) "*/")
+         (seq "//" (repetition 1 +inf.0 (char-complement #\newline)) #\newline))
         (token 'COMMENT lexeme #:skip? #t)]
        [(union #\tab #\space #\newline) (get-token input-port)]
        [(union "CHIP" "IN" "OUT" "PARTS:") lexeme]
diff --git a/beautiful-racket/br/demo/hdl/tst/tokenizer.rkt b/beautiful-racket/br/demo/hdl/tst/tokenizer.rkt
index 3e78632..6c78f48 100644
--- a/beautiful-racket/br/demo/hdl/tst/tokenizer.rkt
+++ b/beautiful-racket/br/demo/hdl/tst/tokenizer.rkt
@@ -9,7 +9,9 @@
     (define get-token
       (lexer
        [(eof) eof]
-       [(seq "/*" (complement (seq any-string "*/" any-string)) "*/")
+        [(union
+         (seq "/*" (complement (seq any-string "*/" any-string)) "*/")
+         (seq "//" (repetition 1 +inf.0 (char-complement #\newline)) #\newline))
         (token 'COMMENT lexeme #:skip? #t)]
        [(union #\tab #\space #\newline) (get-token input-port)]
        [(union "load" "output-list" "set" "eval" "output" (char-set ",;")) lexeme]