Editor: center/pad the level, fix some bugs with pencil drawing

index.html

@@ -191,7 +191,12 @@
             also deal with levels vs level /packs/ somehow, not sure how that'll work (including downloading them, yeargh?)
             -->
         </header>
-        <div class="level"><!-- level canvas and any overlays go here --></div>
+        <div class="editor-canvas">
+            <div class="-container">
+                <!-- level canvas and any overlays go here -->
+                <!-- the container is to allow them to scroll as a single unit -->
+            </div>
+        </div>
         <nav class="controls">
             <div id="editor-toolbar">
                 <!-- tools go here -->