I throw around statements like "game is only 15% done" sometimes without explanation. Since the game has been sitting at 15% done for some time now, I thought I could at least enumerate the high-level systems/parts as I see them.
These are in no particular order, though I will maybe try to group them by relevance. I'm also working from a few different sources of my notes so something may slip through the cracks and I will come back and add it later. I will provide more detail on the physics integration because I've been working on that for months now and have a pretty good idea of what major steps are left to do.
-Physics (a broad category under which is..)
-rigid body "integration" (motion) [done, not in game]
-collision detection (player->world) [done, in game]
-collision detection (player->objects) [done, in game]
-collision resolution (player->world, static objects) [done, in game]
-collision detection (objects->world) [in prototype phase]
-collision detection (objects->objects)
-collision resolution (objects)
-collision resolution (player->objects)
-physics networking (more efficient than what has been prototyped)
-joints (hinges, hooks, glue)
-links (ropes, springs)
-flowing water (water falls, etc.)
-local effects (non-networked client-side physics for explosions, cloth, etc.)
[Automatically included in the above are full-scale objects like boats because the engine doesn't care about size.]
-AI for creatures and NPCs
-NPC conversation system
-player race/model/stats selection
-create some creatures and NPCs
-food/drink -> hunger/thirst/fatigue
-pipes (for water or steam)
-documented modding API
-Mythruna.com store integration
-music (thematic and context sensitive)
-player history tracking
-mountains, deserts, tundras (including temperate-specific flora and fauna)
-random town, city, road/path generation (including support for controlling from a mods)
-random dungeon generation (including support for controlling from a mods)
As said, those are in no particular order. My current plan is to get the physics system to the next working state which would include objects that behave physically... and hopefully object->object collisions if I can get them stable.
The next thing I will work on is the combat system prototype to nail down some ideas that I have about combat. If I come to some conclusions then we'll at least see some PvP combat in the game just for fun and testing (no hitpoints yet).
The next major thing to go in will be AI. AI and Physics are constant CPU drains more than any other feature. I'm trying to tackle those types of things first because then I can get an idea of what the minimum system requirements will be for the final game. There are any number of performance improvements I can make after that but it will give us all a pretty conservative guess at how the final game will run.
Along those lines, animation will be the next thing. Properly done, this will tap into physics and potentially be a small CPU drain on both single player and multiplayer. I don't know yet for sure. And it will be easier to test once AI is in place because I won't have to log in twice just to test.
There are lots of things crammed in the cracks and crevices of that list. My to-do list and whiteboard are filled with items that don't directly appear on that list at all.
...but the list is the basic idea.