Allow selecting elevation level with up/down buttons

public/index.html

@@ -137,7 +137,7 @@
       </div>
 
       <div class="select-elevation">
-        <button>🡅</button>
+        <button class="up">🡅</button>
         <input type="radio" id="select-elevation-3" name="select-elevation" value="3" />
         <label for="select-elevation-3">3</label>
         <input type="radio" id="select-elevation-2" name="select-elevation" value="2" />
@@ -148,7 +148,7 @@
         <label for="select-elevation-0">0</label>
         <input type="radio" id="select-elevation-basement" name="select-elevation" value="-1" />
         <label for="select-elevation-basement">-1</label>
-        <button>🡇</button>
+        <button class="down">🡇</button>
       </div>
 
       <div id="dice">