Assessing the Threat

[foadiron]

I simply can not kill all of the aliens in challenge mode on this level. i have tried all guns, all infernos, or all guns and 1, 2 or 3 infernos. No matter what I do one alien always escapes!

How do you do you kill all of the aliens here in challenge mode?

[Nazrac]

I did it with 1 inferno and the rest guns. Place the inferno at the spot closest to the cores. Then fill up the rest of the spots with guns.

[Bilateralrope]

I was having the same problem. This is how I solved it:
http://img40.imageshack.us/img40/7922/threatv.jpg (http://img40.imageshack.us/i/threatv.jpg/)

Each marked square gets an inferno, Every other square gets a gun. You need all that firepower.