diff --git a/assign4.md b/assign4.md
index 243fa2bbe843e5c62eb51a2831140f27a8e612d7..b42cd18de01f6b8ea159abb262d042f8c2b70604 100644
--- a/assign4.md
+++ b/assign4.md
@@ -1,5 +1,5 @@
 # Assignment 4: Documents And MapKit
-**Due: Apr 26, 2020, 11:59:59 pm, v1**
+**Due: Apr 26, 2020, 11:59:59 pm, v1.01**
 
 NOTE THAT THIS IS AN EVOLVING DOCUMENT and will surely change to
 incorporate more information and hints as the two weeks go by. UPDATE
@@ -20,6 +20,13 @@ running version of this app:
 
 ## Tasks
 
+They overall task is to build a cycle-tracking application that uses the GPS
+receiver built in to your phone to record a track of positions that can later
+be loaded and viewed. Save your recorded tracks to a file with extension
+`.gpx436`. Clicking on a saved track in the document browser results in the
+saved track being displayed with an approproiate zoom level. You do not need
+allow tracks to be edited.
+
 The following is a suggested series of steps for you to take, together
 with approximate points that each step will be worth. You can ignore
 all this and just emulate the first video above. Doing that gets you
@@ -30,7 +37,6 @@ building this app methodically.
 
 -Emulate the functionality of the [Circles](https://sedna.cs.umd.edu/436clips/circles.mp4) app from 4/7.
 
-
 In your version:
 - the browser should work,
 - "+" brings up another view controller that allow you to visibly
@@ -117,6 +123,16 @@ struct GPXTrack : Codable {
 [This](assign4Example.gpx436) is an example `GPXTrack` using the default JSON
 serialization to put to a file (use a text editor to look at).
   
+## Notes
+- Using a custom renderer results in continual "Compiler error: Invalid
+  library file" messages. This appears to be a recent [Xcode issue](https://stackoverflow.com/questions/58445093/compiler-error-invalid-library-file-corelocation) and can make debugging with print statements very difficult.
+- Simulate GPS through the debugger's "Features/Location/.." menu.
+- When stopping, and then starting tracking again, you often get a
+  single old location point in the simulator. This does not happen
+  when running on a phone, but I deal with it by tossing the first
+  location I receive after starting tracking.
+  
+
   
 ## Additional Task, and Extra Credit
 Pick one or two of the tasks below for the last 10 points of this project.