i'm often having the problem where a alien is standing just beside the door , my shooters can not seem him so i wanted to ask if i drop a grenade next to the wall or detonate a rocket against that wall near the door will it go through and kill the alien
Your high explosives will not kill aliens hiding directly behind a wall, but they SHOULD. This should be a feature of explosive weapons, to compensate for the
huge hole in gameplay balance that is the lack of destructible environments (which in turn are only there due to significant technical challenges of implementing them in the near term, not as a matter of balance design, if I am not mistaken).
It should be made a
feature that explosive blasts cause some degree of damage directly through a wall, perhaps even full damage through walls not thicker than 1 tile. Because a big part of modern day infantry rocket launchers is to demolish defensive hold outs like bunkers, if the enemy insists on not relocating or counter attacking (which the aliens often don't, they simply take pot shots from their structure).
It's a vital counter to camping in many situations that's currently missing form the game, even though it would be no where near as difficult to implement as destructible environments and would thus make an excellent interim solution.
As a side benefit, the rocket launcher which is strangely about twice as accurate as the sniper rifle and almost entirely more useful, could have a more reasonable balance and realistic role if one of its primary abilities/advantages was to kill held up enemies that most weapons couldn't touch (without getting very, very close).
I would even say that to further counter structure camping in maps with sparse cover for advancing grenadiers, the high velocity electromagnetic accelerators- the railguns, coilguns and particle beams, should penetrate right though walls that are not more than one tile thick.
Then clearing a building, with one camping alien with a particle beam, where there isn't sufficient cover for a grenadier or CQC specialist to close the distance, wouldn't necessarily cost so many lives. And the aliens could and should use the same advantage against you, so that you can't always get away with simple and extended camping strategies either.