In my WordPress admin I saw there was an update for Startup from 2.0.3 to 2.5, which I performed. After the update the navigation menu has a new label called Menu with a checkbox next to it. Here are screenshots from before and after (to see all at once go to Startup before and after update screenshotsl:
Also, as can be seen from the screenshots, the navigation menu doesn’t collapse when viewed from a mobile device.
The live site with the updated Startup theme can be seen at: