I also moved the buildings around, too. I was previewing the game in Unity's 'free aspect' view, rather than 16:9 or 5:4, but I now realise that there is less screen width to fill.
I tried CamStudio to record my screen, but the quality was terrible. Does anyone have a good (free!) alternative suggestion?
Next step: animating the victims! I need to make some adjustments to the beam when the UFO is at the extreme left or right. I'll also set up an IndieDB account and upload a beta version for testing.