Minor fixes.

theme/style.less

@@ -27,6 +27,10 @@
     color: black !important;
 }
 
+.play-button.play-button-full {
+    &:extend(.ui.inverted.button all);
+}
+
 .getting-started-btn {
     &:extend(.ui.button all);
     &:extend(.orange all);
@@ -45,10 +49,6 @@
     margin-bottom: 0px;
 }
 
-.blocklyTreeSelected {
-    background-color: #1B1C1D !important;
-}
-
 /* Blockly toolbox font size same as the page font */
 .blocklyTreeLabel {
     font-family: @pageFont !important;