diff --git a/mpv-yt-helper.scm b/mpv-yt-helper.scm
index 1e57ef6..2732d3c 100644
--- a/mpv-yt-helper.scm
+++ b/mpv-yt-helper.scm
@@ -5,41 +5,53 @@
 	(srfi srfi-1)
 	(os process))
 
+;; backtrace is set for debugging purposes
 (debug-enable 'backtrace)
 
+;; 720p, high quality audio as default youtube-dl format codes
 (define defaults `((preferred-audio-codes . ("234" "311"))
  		  (preferred-video-codes . ("232"))))
 
-(define test-url "https://www.youtube.com/embed/1xVkRh7mEe0")
+;;(define test-url "https://www.youtube.com/embed/1xVkRh7mEe0")
 
+;; Need a url
 (define read-url
-  (if (not test-url)
-    (read-line read-url)
-    test-url))
+;  (if (null? test-url)
+    (read-line))
+;    test-url))
 
+;; Match a given line with regex for audio and video format strings
 (define (match-audio-format line)
   (string-match "([0-9]{3,}-?).*audio only.*\\[en\\] Default\\, (high|low).*" line))
 
 (define (match-video-format line)
   (string-match "([0-9]{3,}).* ([0-9]{3,}x[0-9]{3,}).*([0-9]{2,}) \\|.* ([0-9]{1,}k).*(video only).*" line))
 
+;; http request to youtube
 (define yt-dlp-port (open-input-pipe (string-append "yt-dlp --no-warnings --list-formats " read-url)))
 
+;; Printing values while building in progress
 (format #t "URL: ~a\nPREFERRED-VIDEO-CODES: ~a\nPREFERRED-AUDIO-CODES: ~a\n\n"
   read-url
   (cdr (assoc `preferred-video-codes defaults))
   (cdr (assoc `preferred-audio-codes defaults)))
 
+;; A function to fetch formats from an input port
 (define (fetch-formats port)
 
+  ;; To iterate through format strings, to control program resource footprint
   (define (iterate line audio-code-list video-code-list)
     (let ((this-line (get-line port)))
 
+      ;; End of file from input - are we there yet?
       (if (eof-object? this-line)
+	;; Yes
         (values (reverse (append audio-code-list video-code-list)))
+	;; No
 	(let ((video-match (match-video-format this-line))
               (audio-match (match-audio-format this-line)))
 
+	  ;; Switch on video or audio match
 	  (cond
 	    (video-match
               (let ((video-code (match:substring video-match 1))
@@ -48,6 +60,7 @@
                     (video-bitrate (match:substring video-match 4))
                     (video-moreinfo (match:substring video-match 5)))
 
+		;; Call iterate with the current audio list and the conjunction of this line with the current video list
                 (iterate this-line audio-code-list (acons video-code (string-append
 						       video-resolution ","
 						       video-framerate ","
@@ -56,11 +69,15 @@
               (let  ((audio-code (match:substring audio-match 1))
                      (audio-quality (match:substring audio-match 2)))
 
+		;; Call iterate with the conjunction of this line with the current audio list and the current video list
                 (iterate this-line (acons audio-code audio-quality audio-code-list) video-code-list)))
 	    (else
+	      ;; No match
 	      (iterate this-line audio-code-list video-code-list)))))))
+    ;; First call of iterate
     (iterate get-line '() '()))
 
+;; Return a list of formats that match preferred codes
 (define (select-formats formats-list)
   (let* ((preferred-audio-codes (cdr (assoc `preferred-audio-codes defaults)))
 	(preferred-video-codes (cdr (assoc `preferred-video-codes defaults))))
@@ -68,19 +85,28 @@
     (format #t "CAAR FORMATS LIST: ~a\n" (caar formats-list))
 
     (define (preferred-video-formats this-alist return-list)
+      ;; Check for empty list
       (if (not (null? this-alist))
 	(if (member (caar this-alist) preferred-video-codes)
+	  ;; Preferred code found
           (preferred-video-formats (cdr this-alist) (cons (caar this-alist) return-list))
+	  ;; Not found
 	  (preferred-video-formats (cdr this-alist) return-list))
+	;; First in, last out
 	(reverse return-list)))
 
     (define (preferred-audio-formats this-alist return-list)
+      ;; Check for empty list
       (if (not (null? this-alist))
 	(if (member (caar this-alist) preferred-audio-codes)
+	  ;; Preferred code found
           (preferred-audio-formats (cdr this-alist) (cons (caar this-alist) return-list))
+	  ;; Not found
 	  (preferred-audio-formats (cdr this-alist) return-list))
+	;; First in, last out
 	(reverse return-list)))
 
+    ;; Return lists as a list
     (values (cons (preferred-audio-formats formats-list `()) (preferred-video-formats formats-list `())))))
 
 
@@ -88,8 +114,11 @@
 ;; Main
 (let* ((formats (fetch-formats yt-dlp-port))
       (codes (select-formats formats))
+      ;; Set the call to mpv on the command line, grabbing the first audio code and the first video code.
       (mpv-commandline (string-append "mpv --ytdl-format=" (caar codes) "+" (cadr codes) " " read-url)))
   
+  ;; Shell call
   (system mpv-commandline))
 
+;; All done with the youtube input port
 (close-port yt-dlp-port)