how to design a small cabin to build myself

• I want to build a shed-sized cabin, but don't know how to design it, in terms of making it attractively-proportioned and inviting to be inside of. It must be shed-sized (treehouse-sized) in that its floor plan can't exceed 120 sq ft, so we can make it without planning permits or beaurocracy. The site is on a steep hillside with a wonderful view south down a wooded valley out over the ocean; the hill is right behind at the back, and there are trees at the sides. So the cabin should probably have a big window in the south wall, and a door at the west. It will sit on a deck/platform, which I'm making now on a foundation of reinforced concrete piers on rock. There will be some deck on the south side of the cabin. The cabin should be wood-frame, because that's what I can do. I've a Skil saw, hammer, and similar basic tools, although my construction experience is limited to a bit of Habitat work and helping friends with projects. Things like the Loftcube are out of my range. Cost has to be kept minimal, too; I expect I'll do interior finish work later. Outer walls and roof will be enough to start with. The cabin will be used mainly as a place for escape, writing, meditation, and art, not a permanent living space, but it would be nice to sleep there (I've often camped there in a tent). It's about 100 yards from our house, up a steepish trail. It won't have electricity or water. What I need now please is advice about the design, and how to make it a pleasant space to be inside of. What proportions would work? I can do layout plans and figure the contruction details once the space itself is designed. General ideas of what's easy to build (flat roof sounds simple, but pitched roof could allow a sleeping loft) would also be great.

• Answer:

  As a followup: a very small cabin is nearly built. It's about 6'x10' with most of the (10') south wall glass, a window in the east wall, and a door in the west. We're at the sheetrock stage now, sheathed but no siding yet. I was given a chop saw for my birthday, which has been invaluably easier for framing than the Skil saw. The site is really fabulous, but the cabin is very minimal, just enough space for a bed and a desk (plus the deck of course.) There are some more very low-res pics on http://www.flickr.com/photos/anadem/sets/929119/, but no pics of the latest stages yet. Next project is a biggish treehouse, perhaps along the lines of http://ask.metafilter.com/mefi/5890 though higher off the ground, in a group of redwoods. No view, but very cool in the heat.