Ok so it seems this part of the forum is related to game ideas for the future, so here are mine:
Many people have said the word "sandbox" so far, so why not think of a sort of "Minecraft" game ? There wouldn't be a "block for block" concept, but you would need a certain amount of resources to build tools, weapons, or shelters. As Outerra is already capable of terrain distortions (= create hills or holes with e.g. the "left click weapon"), I don't believe it's an impossible concept.
First of all you'd need to punch the trees (as long as they are in 2D it wouldn't be difficult
), with wood you can create powerful tools to gather stone (from the bare rock mountainsides, or from the occasional rock formation if you play on flatlands), and metal ores and other resources would spread differently according to the biomes (like diamond in the African desert, etc.) When you gather dirt or stone it would create a hole (like the left click weapon does already) and if you drop it anywhere else it would create a small "hill".
You would need these resources in order to build useful constructions (not custom buildings made of blocks like Minecraft, but 3D models stored in your object database with numeric values for the amounts of material necessary for building - it's a bit closer to the Banished concept than the Minecraft one). Finally, animals, mobs, and perhaps NPCs would be part of the world as well.
Based on all of this, players could be able to create everything in their area of the multiplayer planet, and invite other players to test their creations: racing games, naval battles, flight simulations, geocaching games, etc. etc.
Did I find a good idea ?