lookout tower/deer stand/observation deck

I have a high point on my property that overlooks a small canyon (they call it a draw here in WY) and if you get up about 6-10 feet higher you can see all the way down into the canyon. I've been musing about building a deck there with a ladder to climb up to a platform that's just big enough to put an air mattress and sleeping bag on it and sleep under the stars on nights when it's not freezing or overcast or a full moon. Since lumber prices have gone down a bit, I was thinking about using 4x4x12's. My question is: should they be tilted inward like the legs on an oil derrick or straight up and down?

More information and images are needed for this question.
Are you
- Extending over the edge?
- How far would you fall if you chose too?
- galvanised steel will not degrade.
- Will rails etc be installed?- could rocks be used?

No, I'm not extending over the edge. I envisage a guard rail around the platform just enough to keep one from falling. I would like it to be at least 6 feet off the ground. I'm not sure how I could use rocks. Pacific Steel has 2" angle iron 1/4" thickness for around $60 for a 20' length. A 4x4x12 from Menards is ~$20. If I used wood, I would have to paint it every summer.

Yes, I think they should be tilted inward.  They should also be well braced to one another (triangles are strong, squares aren't) so that it can't tip over to the N, S, E or W and also so that it can't twist and fall down in place.

If you're gonna be sleeping on it, put railings with spindles or some other means of keeping you up there if you roll off unexpectedly.

If you're gonna be hunting from it, plan how high your seat will be (swivel ideally) and then set the railing height so you can see over or under it (preferably over).

Make the transition from ladder to platform safe and stable (handholds) so that when it's slippery with ice you don't fall off.