Build a tower by placing blocks in numerical progression from low at the top to high at the bottom of the tower. Finish your tower before the Vikings finish their tower. Replace the blocks of your tower so that they are in order.
If you do not want to use the open block, try the mystery block. You will receive bonus points if you place blocks in the exact order. For example: Placing 10 above 11. At the end of the level you will receive bonus points for finishing the level and bonus points based on how high the number is at the top of your tower.