work around a problem with answer.sty; see #228

misc/index.start.html

@@ -126,14 +126,14 @@ <h3><a href="https://ic.openlogicproject.org/"><em>Incompleteness and Computabil
       repository.
   </ul>
 
-  <h3><a href="courses/boxes-and-diamonds/"><em>Boxes and Diamonds</em></a></h3>
+  <h3><a href="https://bd.openlogicproject.org/"><em>Boxes and Diamonds</em></a></h3>
 
-    <p><a href="courses/boxes-and-diamonds/"><img src="courses/boxes-and-diamonds/bd.png" /></a>A textbook for modal and other intensional logics based on the Open Logic Project; includes the material on normal modal logic,
+    <p><a href="https://bd.openlogicproject.org/"><img src="https://bd.openlogicproject.org/bd.png" /></a>A textbook for modal and other intensional logics based on the Open Logic Project; includes the material on normal modal logic,
     intutionistic logic, and counterfactuals, with appendices on basic
     set theory and classical propositional logic.</p>
 
     <ul>
-      <li><a href="courses/boxes-and-diamonds/bd-screen.pdf">bd-screen</a>
+      <li><a href="https://bd.openlogicproject.org/bd-screen.pdf">bd-screen</a>
         for screen reading (color, smaller margins, low-res images)</li>
       <li><a href="https://github.com/rzach/boxes-and-diamonds">Source code</a>
         for generating this textbook is on GitHub in a separate

sty/open-logic-defer.sty

@@ -109,6 +109,8 @@
 % - `\collectproblems`: execute this in the preamble to arrange for
 % the printing of problems explicitly, e.g., at the end of the book
 
+\def\nobreak{\penalty\@M} % needed to fix problem with answers.sty
+
 \newcommand{\collectproblems}{%
   % at the end of every \chapter command, write a section header into
   % the .prb file and reset counters