diff --git a/aprendizations/templates/courses.html b/aprendizations/templates/courses.html
index b390591..6b53314 100644
--- a/aprendizations/templates/courses.html
+++ b/aprendizations/templates/courses.html
@@ -12,9 +12,6 @@
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/js/bootstrap.bundle.min.js" integrity="sha384-A3rJD856KowSb7dwlZdYEkO39Gagi7vIsF0jrRAoQmDKKtQBHUuLZ9AsSv4jD4Xa" crossorigin="anonymous"></script>
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.9.1/font/bootstrap-icons.css">
 
-    <!-- font-awesome -->
-    <!-- <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.4/css/all.min.css" rel="stylesheet"> -->
-
     <link rel="stylesheet" href="{{static_url('css/maintopics.css')}}">
     <link rel="stylesheet" href="{{static_url('css/sticky-footer-navbar.css')}}">
     <!-- Scripts -->
@@ -44,9 +41,7 @@
           <ul class="navbar-nav ms-auto">
             <li class="nav-item dropdown">
               <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
-                <i class="bi bi-person-circle"></i>
-                <!-- <i class="fas fa-user-graduate" aria-hidden="true"></i> -->
-                &nbsp;
+                <i class="bi bi-person-circle"></i>&nbsp;
                 <span id="name">{{ escape(name) }}</span>
                 <span class="caret"></span>
               </a>
diff --git a/aprendizations/templates/maintopics-table.html b/aprendizations/templates/maintopics-table.html
index a968512..70062b7 100644
--- a/aprendizations/templates/maintopics-table.html
+++ b/aprendizations/templates/maintopics-table.html
@@ -16,9 +16,6 @@
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/js/bootstrap.bundle.min.js" integrity="sha384-A3rJD856KowSb7dwlZdYEkO39Gagi7vIsF0jrRAoQmDKKtQBHUuLZ9AsSv4jD4Xa" crossorigin="anonymous"></script>
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.9.1/font/bootstrap-icons.css">
 
-  <!-- font-awesome -->
-  <!-- <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.4/css/all.min.css" rel="stylesheet"> -->
-
   <link rel="stylesheet" href="{{static_url('css/maintopics.css')}}">
   <script defer src="{{static_url('js/maintopics.js')}}"></script>
 
@@ -42,7 +39,6 @@
       <ul class="navbar-nav ms-auto">
         <li class="nav-item dropdown">
           <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
-            <!-- <i class="fas fa-user-graduate" aria-hidden="true"></i> -->
             <i class="bi bi-person-circle"></i>
             &nbsp;
             <span id="name">{{ escape(name) }}</span>
@@ -109,34 +105,22 @@
           <tr>
             <th scope="row" class="text-muted text-center">
               {% if t['type']=='chapter' %}
-                <!-- <i class="fas fa-flag"></i> -->
-                <i class="bi bi-flag-fill"></i>
+                <i class="bi bi-flag-fill"></i>&nbsp;
               {% elif t['type']=='learn' %}
-                <!-- <i class="fas fa-book"></i>&nbsp; -->
-                <!-- <i class="bi bi-book-fill"></i>&nbsp; -->
-                <h5>
                 <i class="bi bi-book"></i>&nbsp;
-                </h5>
-
               {% else %}
-                <i class="fas fa-pencil-alt"></i>&nbsp;
-                <i class="bi bi-pencil-fill"></i>&nbsp;
                 <i class="bi bi-pencil"></i>&nbsp;
               {% end %}
             </th>
             <td>
               <div class="text-muted">
                 {% if t['ref'] not in course['goals'] %}
-                  <!-- <i class="fas fa-puzzle-piece"></i> -->
-                  <i class="bi bi-puzzle-fill"></i>
+                  <i class="bi bi-puzzle-fill"></i>&nbsp;
                 {% end %}
-
-
                 {{ t['name'] }}
               </div>
             </td>
             <td class="text-center">
-              <!-- <i class="fas fa-lock text-muted"></i> -->
               <i class="bi bi-lock-fill text-muted"></i>
             </td>
           </tr>
@@ -147,46 +131,49 @@
             <th scope="row" class="text-primary text-center">
               {% if t['type']=='chapter' %}
                 <span class="text-nowrap" data-toggle="tooltip" data-placement="bottom" title="Fim do capítulo">
-                <!-- <i class="fas fa-flag-checkered"></i>&nbsp; -->
-                <i class="bi bi-flag-fill"></i>&nbsp;
+                  <h5>
+                    <i class="bi bi-flag-fill"></i>&nbsp;
+                  </h5>
                 </span>
               {% elif t['type']=='learn' %}
                 <span class="text-nowrap" data-toggle="tooltip" data-placement="bottom" title="Texto com matéria">
-                <!-- <i class="fas fa-book"></i>&nbsp; -->
-                <!-- <i class="bi bi-book-fill"></i>&nbsp; -->
-                <i class="bi bi-book"></i>&nbsp;
+                  <h5>
+                    <i class="bi bi-book"></i>&nbsp;
+                  </h5>
                 </span>
               {% else %}
                 <span class="text-nowrap" data-toggle="tooltip" data-placement="bottom" title="Exercícios">
-                <!-- <i class="fas fa-pencil-alt"></i>&nbsp; -->
-                <!-- <i class="bi bi-pencil-fill"></i>&nbsp; -->
-                <i class="bi bi-pencil"></i>&nbsp;
+                  <h5>
+                    <i class="bi bi-pencil"></i>&nbsp;
+                  </h5>
                 </span>
               {% end %}
             </th>
             <td class="text-primary">
               {% if t['ref'] not in course['goals'] %}
                 <span class="text-nowrap" data-toggle="tooltip" data-placement="bottom" title="Pré-requisito para este curso">
-                <!-- <i class="fas fa-puzzle-piece"></i> -->
-                <i class="bi bi-puzzle-fill"></i>
+                  <h5>
+                    <i class="bi bi-puzzle-fill"></i>
+                  </h5>
                 </span>
               {% end %}
-
               {{ t['name'] }}
             </td>
 
             <td class="text-center">
               {% if t['level'] < 0.01 %}
-                <!-- <i class="fas fa-lock-open text-success"></i> -->
-                <i class="bi bi-unlock-fill text-success"></i>
-
+                <h5>
+                  <i class="bi bi-unlock-fill text-success"></i>
+                </h5>
               {% elif t['type']=='chapter' %}
-                <!-- <h5><i class="fas fa-award text-warning"></i></h5> -->
-                <i class="bi bi-award-fill"></i>
-
+                <h5>
+                  <i class="bi bi-award-fill"></i>
+                </h5>
               {% else %}
                 <span class="text-nowrap text-warning" data-toggle="tooltip" data-placement="bottom" title="{{round(t['level']*5, 3)}}">
-                  {{ int(t['level']*5+0.25)*'<i class="bi bi-star-fill"></i>' }}{% if int(t['level']*5+0.25) < 5 %}{{'<i class="bi bi-star-half"></i>' if 0.25 <= t['level']*5-int(t['level']*5) < 0.75 else '<i class="bi bi-star"></i>'}}{% end %}{{ (4-int(t['level']*5+0.25))*'<i class="bi bi-star"></i>' }}
+                  <h5>
+                    {{ int(t['level']*5+0.25)*'<i class="bi bi-star-fill"></i>' }}{% if int(t['level']*5+0.25) < 5 %}{{'<i class="bi bi-star-half"></i>' if 0.25 <= t['level']*5-int(t['level']*5) < 0.75 else '<i class="bi bi-star"></i>'}}{% end %}{{ (4-int(t['level']*5+0.25))*'<i class="bi bi-star"></i>' }}
+                  </h5>
                 </span>
               {% end %} <!-- if -->
             </td>
diff --git a/aprendizations/templates/rankings.html b/aprendizations/templates/rankings.html
index 38e5cf1..5d064a8 100644
--- a/aprendizations/templates/rankings.html
+++ b/aprendizations/templates/rankings.html
@@ -12,9 +12,6 @@
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/js/bootstrap.bundle.min.js" integrity="sha384-A3rJD856KowSb7dwlZdYEkO39Gagi7vIsF0jrRAoQmDKKtQBHUuLZ9AsSv4jD4Xa" crossorigin="anonymous"></script>
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.9.1/font/bootstrap-icons.css">
 
-  <!-- font-awesome -->
-  <!-- <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.4/css/all.min.css" rel="stylesheet"> -->
-
   <link rel="stylesheet" href="{{static_url('css/maintopics.css')}}">
   <script defer src="{{static_url('js/maintopics.js')}}"></script>
 
@@ -38,9 +35,7 @@
       <ul class="navbar-nav ms-auto">
         <li class="nav-item dropdown">
           <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
-            <!-- <i class="fas fa-user-graduate" aria-hidden="true"></i> -->
-            <i class="bi bi-person-circle"></i>
-            &nbsp;
+            <i class="bi bi-person-circle"></i>&nbsp;
             <span id="name">{{ escape(name) }}</span>
             <span class="caret"></span>
           </a>
@@ -58,7 +53,6 @@
   <h1 class="display-6">{{ course_title }}</h1>
 
 <table class="table table-sm table-hover">
-  <!-- <col width="100"> -->
   <thead>
     <tr>
       <th scope="col" class="text-center">Posição</th>
@@ -71,12 +65,10 @@
     <tr class="{{ 'table-secondary' if r[0] == uid else '' }}">
       <td class="text-center"> <!-- rank -->
         <strong>
-          <!-- {{ '<i class="fas fa-crown fa-lg text-warning"></i>' if i==0 else i+1 }} -->
-          <!-- {{ '<h3><i class="bi bi-mortarboard-fill text-warning"></i></h3>' if i==0 else i+1 }} -->
           {{ '<h3><i class="bi bi-trophy-fill text-warning"></i></h3>' if i==0 else i+1 }}
         </strong>
       </td>
-      <td> <!-- student name -->
+      <td> <!-- first and last name -->
         {{ ' '.join(r[1].split()[n] for n in (0,-1)) }}
       </td>
       <td> <!-- progress -->
diff --git a/aprendizations/templates/topic.html b/aprendizations/templates/topic.html
index 845e563..0e51ca3 100644
--- a/aprendizations/templates/topic.html
+++ b/aprendizations/templates/topic.html
@@ -14,9 +14,6 @@
     <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/js/bootstrap.bundle.min.js" integrity="sha384-A3rJD856KowSb7dwlZdYEkO39Gagi7vIsF0jrRAoQmDKKtQBHUuLZ9AsSv4jD4Xa" crossorigin="anonymous"></script>
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.9.1/font/bootstrap-icons.css">
 
-    <!-- font-awesome -->
-    <!-- <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.15.4/css/all.min.css" /> -->
-
     <!-- mathjax -->
     <script>
       MathJax = {
@@ -63,7 +60,7 @@
           <ul class="navbar-nav">
             <li class="nav-item"><a class="nav-link" href="/courses">Cursos</a></li>
             <li class="nav-item"><a class="nav-link active" aria-current="page" href="/course/{{course_id}}">Tópicos</a></li>
-            <!-- <li class="nav-item"><a class="nav-link disabled" href="#">Classificação</a></li> -->
+            <li class="nav-item"><a class="nav-link disabled" href="#">Classificação</a></li>
           </ul>
           <ul class="navbar-nav ms-auto">
             <li class="nav-item dropdown">
diff --git a/demo/math/learn-prime-numbers/learn.yaml b/demo/math/learn-prime-numbers/learn.yaml
new file mode 100644
index 0000000..4f5ede1
--- /dev/null
+++ b/demo/math/learn-prime-numbers/learn.yaml
@@ -0,0 +1,17 @@
+- type: radio
+  title: O que são números primos?
+  text: |
+    Um número $n \ge 2$ é primo se os únicos divisores forem $1$ e $n$.
+
+    Por exemplo, o número $5$ é primo, pois $2,3,4$ não são divisores de $5$.
+
+    ---
+
+    O número $1$ é primo?
+  options:
+    - Não
+    - Sim
+  max_tries: 1
+  solution: |
+    O número $1$ não é primo. Apenas podem ser primos os números a partir do
+    $2$.
--
libgit2 0.21.2