I was going for the area denial achievement. It turns out though that despite not building a single sniper, making it impossible to destroy a glider, I did not get the achievement. I did not destroy a single glider factory either. That map took a long time to do and I am not happy about it.
It appears that the achievement is possible, however, as 1.7% of players on the steam version have completed it. That isn't an insignificant number. (http://steamcommunity.com/stats/280220/achievements)
How come I did not get the achievement then? I did not even build a single sniper.
Did a glider destroy one of your units? That might have made you fail it. (does a self-destructing glider still count as destroyed glider?)
A glider did destroy a unit. I wish the achievement would also say to not lose any units to gliders if that is the case then.
If the achievement was to not allow any units destroyed by gliders, then you could build as many snipers as you wanted and the achievement would be too easy. When a glider kills one of your buildings, it also destroys itself, rendering the achievement void.
I said to also include that text to make the achievement more clear. It is annoying when you grind through all of the creeper only to find out that you also can not loose a single unit to gliders.
I think the point he's making is that if you lose a unit to a glider, the glider is also being destroyed. The opening text for the mission even points it out. Seems pretty clear to me.
I officially announce that you, invaderhive, have willfully and rightfully gained the prestige of the Area Denial Achievement... with merits. To commemorate this honor I bestow on to you this trophy of greatness. 8)
///////////\\\\\\\\\\
|| Area ||
|| Denial ||
|| Achievement ||
|| Trophy ||
|| ||
\\\\\\\\\\\//////////
||
||
||
||
||
_____||________
| invaderhive |
|_______________|