Thanks for trying out Sprytile! You can see how Unity will render your mesh my turning on Backface Culling. In the right hand side panel of the viewport (press `n` if it isn't visible) expand 'Shading' and toggle Backface Culling on.
There's a way to make faces double sided using a utility that comes with Sprytile, covered in the advanced documentation.
Hope to see the cool stuff you make with Sprytile!