I plan on having several game modes: (copied and pasted from the blog)
Creative mode
You’ve got infinite materials and build without any delay. Can be played both as singleplayer and as multi player.
You can share the maps with other players somehow. Perhaps just share the actual .level file manually?
Survival mode
Singleplayer / cooperative. You have a health bar and need to eat in order to keep healthy. You have to gather the materials you wish to use, and construction takes time. Mining through stone is slower than through dirt.
Monsters, animals, play on levels made in Creative mode, or play on random levels.
Does this mode need a goal?
Team survival mode
Same as Survival mode, except players are divided into two or more teams.
Fortress mode
After having built a level in Creative or Survival mode, you and your friends connect to another fortress made by some other people. The map gets bigger so it fits both maps, and you play a game on this map. Perhaps Capture the Flag, perhaps something else
The last two modes will have weapons and fighting. Probably with arrows with proper physics, so you'd aim diagonally up towards whatever you want to hit.
The game engine was written from scratch in java. The visibility culling is very naive still, it just culls against the view frustum. I'd like to do some occlusion culling as well as that would really speed up the indoors areas.
The map is randomly generated.