Logo Appears Stretched in Mobile View

The square logo becomes rectangle in mobile view, even when I make it the recommended dimensions (150x150 pixels). Is there a certain dimensions I should set for the logo so it will be square when viewing from mobile device? Or perhaps some css codes to add? The website is http://kidzkatch.com/ and the logo becomes stretched when viewing through a cell phone or tablet. I need to figure out a way to fix this. Thanks