Aetherius is a voxel based game experiment being written in Java with LWJGL. It provides a procedural universe that runs infinitely in every direction across infinite worlds, with thousands of materials. All the non-procedural content is made with a suite of software that ships as part of the game. Aside from the pre-baked content and the modder, the game also procedurally generates content from mixing and matching an abundance of components that the player has the ability to add to or remove from. This content includes NPCs, Quests, Machinery and Materials. Aetherius is a true sandbox. The player can toggle every single aspect of vanilla gameplay, and construct their own game rules to suit themselves. It is fast approaching a viable alpha test phase.
This screenshot shows one of the branch types that will drop near the base of trees. You use these to make your first tool (you can't just punch trees!), which in turn will allow you to start mining, collecting resources and building your first machines.
Also in the screenshot are four coloured boxes - the positioning isn't final, but these boxes are essentially progress bars that indicate your health, fullness, mana, and stamina.