You must create a set of 6-sided dice and play a game with an opponent. The dice are like regular dice, but you can change the numbers on the dice. For example, regular dice have sides
123456. You could create one with sides
244678 if you want.
The game starts with the opponent selecting any one die. After this, you also must select one (also from the same set). If both of you roll the dice, the probability of you rolling a higher number should be at least 60%.
What is the largest set of such dice that can be created?