How to make the popular product.
If you want to invent something popular, do not focus on a product itself.
You should carefully consider what is the problem.
The product is just means to solve the problem.
If you come up with goods idea before you check problem in need, you would be fail.
First of all, think about what is in need.
For instance, you should not start to train about curry unless currey is really in fashion or you love currey.