Board Thread:Game Discussions/@comment-24149689-20140103120654/@comment-24108837-20140103200946

Yes it does go up and down. The levels you get a reward for are tougher than the others. Level 10 is tougher than level 11 and levels 15, 21, 28, 35, 43 and 51 are as tough as 3 levels higher. The level just after It is easier again. On the whole the difficulty rises with the level rise.