So basically I made a huge curving hallway in a mountain and i put a sandbag every other square When enemies come they go into the tunnel to attack your base and trap them in then instead of beating the thing they are trapped in by the beat the sandbags Doesnt work against:
Sappers
I forgot the name but the guys who tunnel around your defences
Yep, Sappers will take the closest way toward your base and clear out the path with pickaxes or grenades.
Not to forget the insect's which come out of the ground at your mountainbase.
Sapper trap:
A single tile corridor with wooden walls on either side, doors held open on both sides of the tunnel. Then we have an IED 3/4th into the tunnel with mortar shells in front, before that a few traps to kill of that first sapper. Behind the wooden wall some turrets.
Explosions will kill and destroy both the raiders and the wooden wall. any remaining raiders are now in the open and can be killed of easily by the turrets.
Triple thick walls around the rest of the base and they will walk right into this trap.
https://imgur.com/7qDp09a (https://imgur.com/7qDp09a)