Dimension of Change and Impermanence

Take Minecraft terrain generation and add a time element. As time passes, blocks in this dimension appear and disappear (even when the player isn't present). Imagine one of those infinite fractal zoom-in videos, with all the weird colors, but it's 3D and you have to survive in it. The crazy terrain might be a bit similar to the "far lands".

Technical thoughts

• Very slow change, not constant
• Don't save chunks unless player-placed blocks currently exist there. If player blocks do exist, only save those blocks and regenerate the world around it.
• Almost all player blocks are temporary, too! Only specific materials avoid decay. Your cobblestone house will desaturate like dead coral and slowly disappear.
• Use the lighting mechanic to determine if player blocks decay. Skylight moves through the natural blocks freely to hit player blocks. I imagine this as coming from underneath, so players can make platforms with the rare special blocks and build freely on top with non-special blocks. It reminds me of a zombie with a helmet in daylight. Maybe players are the zombies here?

Neat ideas

• Make a huge library of simple player-made structures. The terrain generation can randomly embed these over time so it looks like memories of the overworld are popping in and out of the chaos.
• Spatial opposite of The Nether. Instead of 8x smaller, it's much bigger.
• Get to some far-off dark towers made of weird stuff that contain a dangerous baddie
• Link to redstone here somehow for wireless and hidden circuits