Decent.
This a very clean and decent game, hovewer, some addictions could have made it alot better....
Perhaps upgrades or special itens, even tho it was made in 48 hoursm you could have made some of the bombs that the plane sends give us more aliens or something...
Oh and another thing, I only found out that i could move up and down in the last level... you should have made it more clear since the beggining,