Tracey,
Well done.
Everything from the sound used to the layouts of content.
I like how you hade less items on the main screen so it looks like its not all squeezed up together. The sound used very well goes with the theme of the game. The button layout in the control of your Alien is nice.
And changes I would suggest is the colour of the some buttons is too transparent that the white in the background hits the white text so its not real visible also with your title, it could've used a different font or stretched out a bit
But otherwise.
Great Job!!!...