add notices to those who wish for a greater challenge

We add the following level-3 header to help people identify text
they may wish to skip if they wish for a greater challenge:

```
```

After that notice we add:

```
**If you want a greater challenge, don't read any further**:
just try to understand the program via the source.

If you get stuck, come back and read below for additional hints and information.
```

And sometimes follow with:

```
```

Or sometimes follow with:

```
```

Where the alt code impacts a "greater challenge", we add instead:

```
**If you want a greater challenge, don't read any further**:
just try to understand the program without looking at the Alternate code.

If you get stuck, come back and look at the Alternate code.
```

And where a given command impacts a "greater challenge", we add instead:

```
**If you want a greater challenge, don't read any further**:
just try to understand the program without running the command below.

If you get stuck, come back and run the following command:
```

Perform `make www` to perform the above and test under macOS.

1994/imc/README.md

@@ -44,7 +44,16 @@ parameter or an invalid parameter is given, then 5 is assumed.  The
 maximum parameter is determined only by the amount of CPU time, virtual
 memory and display (or file) space available.
 
-### OBFUSCATION:
+
+### NOTICE to those who wish for a greater challenge
+
+**If you want a greater challenge, don't read any further**:
+just try to understand the program via the source.
+
+If you get stuck, come back and read below for additional hints and information.
+
+
+### How this entry works:
 
 OK, so you have probably seen magic square printers before.  But what
 about one that deals with even sizes as well as odd ones, or one that

1994/imc/index.html

@@ -424,7 +424,11 @@ other functions (apart from <code>main()</code>).</p>
 parameter or an invalid parameter is given, then 5 is assumed. The
 maximum parameter is determined only by the amount of CPU time, virtual
 memory and display (or file) space available.</p>
-<h3 id="obfuscation">OBFUSCATION:</h3>
+<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge</h3>
+<p><strong>If you want a greater challenge, don’t read any further</strong>:
+just try to understand the program via the source.</p>
+<p>If you get stuck, come back and read below for additional hints and information.</p>
+<h3 id="how-this-entry-works">How this entry works:</h3>
 <p>OK, so you have probably seen magic square printers before. But what
 about one that deals with even sizes as well as odd ones, or one that
 prints out a different one each time (or attempts to, at any rate)?</p>