From the title screen, click "Start" to begin the game. You may also click "Help" for an explanation on how to play. Once you click Start, you will see a short intro movie. You can skip the intro movie by clicking "Skip" in the upper left corner. Whether the block is discarded, or if you switch the block with one from your tower, that block will go to the viking's side. You still cannot see the viking tower, but you will be able to see where they placed their brink on the stack. They will swap or discard a block, send a block back, and the process begins anew.