diff --git a/ace/index.html b/ace/index.html
index e7f34f5..de01e1e 100644
--- a/ace/index.html
+++ b/ace/index.html
@@ -58,7 +58,7 @@
             <!--<button id="btnSave" onClick="save()" class="btn btn_g">save</button>-->
             <button id="btnUndo" onClick="editor.undo()" class="btn">↶</button>
             <button id="btnRedo" onClick="editor.redo()" class="btn btn_g">↷</button>
-          	<button id="btnFs" onclick="toggleFullscreen()" class="btn">◻</button>
+          	<button id="btnFs" onclick="toggleFullscreen()" class="btn">FS</button>
         </div>
         <div class="inner" id="editor"></div>
         
@@ -80,8 +80,9 @@
             });
 
             function updateToolbar() {
-                document.getElementById("btnUndo") = !editor.session.getUndoManager().hasUndo();
-                document.getElementById("btnRedo") = !editor.session.getUndoManager().hasRedo();
+                document.getElementById("btnUndo").disabled = !editor.session.getUndoManager().hasUndo();
+                document.getElementById("btnRedo").disabled = !editor.session.getUndoManager().hasRedo();
+                document.getElementById("btnFs").visible = !window.fullScreen;
             }
             editor.on("input", updateToolbar);