To reinforce what previous people have said, have a combination of simplicity and complexity. For example, the 2004 game had an excellent example of that. The less experienced teams and simple robots could make a positive contribution by corralling balls back into the player station. While the more experienced teams could focus on whether they wanted to go hang, score a capper ball or both. It added a challenge for all levels and thats what is needed year after year to make a good game.