There's this game on the App Store (I believe it's on Android too) called The Blockheads. It's kind of like 2D Minecraft, but it has jetpacks and portals and things, and you can easily (not much coding - can be expensive in in-game currency, which is time crystals) make online servers which can be found by lots of different players. It's a pretty fun game, I recommend it to you guys. I have a server, and if you want to join it, just click this link once you have the game:
http://theblockheads.net/join.php?id=55 ... BLOCKLANDS
Baa.