The most important thing in this game is choosing a defensible position for a base. Generally the best place to look for is a natural inset in the mountainside. Then dig inward and establish your most important assets inside. Another important thing to note is that you can defend a lot better if enemies do not have a direct line of sight with your base until they are in range.
Illustration

(note: This is the absolutly ideal spot, even better if you find thermal vents there)
Raiders tend to hug the walls as they assault you, so mines are your best friend.
I don't use waffling or "kill rooms" and this has been a standard set up for me.
If you can't find any kind of natural inset, start digging one out, the first 3 raids should be pretty easy to defend.
I have about 12 colonists on Kassandra (evil bitch) and i regularly take out raiding parties of over 30 raiders without breaking a sweat. hope this helps...
Illustration

(note: This is the absolutly ideal spot, even better if you find thermal vents there)
Raiders tend to hug the walls as they assault you, so mines are your best friend.
I don't use waffling or "kill rooms" and this has been a standard set up for me.
If you can't find any kind of natural inset, start digging one out, the first 3 raids should be pretty easy to defend.
I have about 12 colonists on Kassandra (evil bitch) and i regularly take out raiding parties of over 30 raiders without breaking a sweat. hope this helps...