convert spoiler language and towards deobfuscation language

2011/zucker/README.md

@@ -153,7 +153,7 @@ reflection ray at an object's surface, given the incoming
 direction and surface normal.
 
 
-#### Further details (contains spoilers):
+#### Further deobfuscation:
 
 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 +480,7 @@ 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-contains-spoilers">Further details (contains spoilers):</h4>
+<h4 id="further-deobfuscation">Further deobfuscation:</h4>
 <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