Language, history and curiosities in games.
Balance is not the same thing as fun.
Fun is about learning in a context where there is no pressure from consequence, and that is why games matter.
There are many ways we find fun in games, and I will talk about the others. But learning is the one I believe to be the most important.
Fun from games arises out of mastery. It arises out of comprehension. It is the act of solving puzzles that makes games fun. In other words, with games, learning is the drug.
I still find it interesting to make games as simple as possible, without losing the fun.