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.

2011/fredriksson/README.md

@@ -199,7 +199,15 @@ Just say
   (Btw, tcc has its roots in IOCCC...)
 
 
-### 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:
 
 * The initialized char array includes the source code of the real program,
   as well as its name and commands to build and run it, all

2011/fredriksson/index.html

@@ -536,7 +536,11 @@ C99, or long lines as an extension. This code has been tested on:</p></li>
 <li><p>AIX 5.3, IBM eServer p5-550, gcc 3.3.3 and AIX CC Version 6</p>
 <p>(Btw, tcc has its roots in IOCCC…)</p></li>
 </ul>
-<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>
 <ul>
 <li>The initialized char array includes the source code of the real program,
 as well as its name and commands to build and run it, all

2011/hou/README.md

@@ -110,7 +110,15 @@ the actual `argv` strings to be writable, though.
 - Some seemingly redundant code works to eliminate warnings and evade a gcc bug.
 
 
-### Spoilers
+### 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:
 
 The parser parses function names, subtraction, and division as single-letter
 unary operators. A bitmask encoded hash table is used to check no-ops/digits

2011/hou/index.html

@@ -462,7 +462,11 @@ the actual <code>argv</code> strings to be writable, though.</li>
 <li>This program doesn’t work with <code>%e</code> style numbers like <code>1e-4</code>.</li>
 <li>Some seemingly redundant code works to eliminate warnings and evade a gcc bug.</li>
 </ul>
-<h3 id="spoilers">Spoilers</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>The parser parses function names, subtraction, and division as single-letter
 unary operators. A bitmask encoded hash table is used to check no-ops/digits
 and another hash function maps the ASCII to a function ordinal, which is then

2011/zucker/README.md

@@ -153,7 +153,15 @@ reflection ray at an object's surface, given the incoming
 direction and surface normal.
 
 
-#### Further details:
+### 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:
 
 The program is not quite a traditional [ray
 tracer](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)), but a "[sphere

2011/zucker/index.html

@@ -480,7 +480,11 @@ by the source code itself: the geometric construction of a
 reflection ray at an object’s surface, given the incoming
 direction and surface normal.</p></li>
 </ul>
-<h4 id="further-details">Further details:</h4>
+<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>The program is not quite a traditional <a href="https://en.wikipedia.org/wiki/Ray_tracing_(graphics)">ray
 tracer</a>, but a “<a href="sphere-tracing.pdf">sphere
 tracer</a>” which uses distance fields to encode proximity to