The game is partially set outside but the redstone things are set inside. There is a pool of water which is only 1 block deep, because since TU19, however deep you have a pool of water and jump really high and land there, it is safe. In a chest in a middle, there are stacks of sand which you will be used to pile up.
On the other hand, the redstone is quite complicated but it is "relatively simple", as said by Stampy.
The aim of the game is to build a Sand Tower and Switch the Switch. The first person who gets 14 wood planks in their side, then there will be redstone lamps, which will light up if you have 14 wooden planks in your side