We train the brain. Your gaming-style perception. You can just try and realize at what level you will stop.
Do you think it's easy? Complete all 16 levels.

The first levels are introductory.
All levels are designed for a gradual increase in difficulty.
You can train your perception at any level, it depends how much your perception is developed.

Have you completed all the levels and you are happy? You are great =) Do not forget that training must be constant if you want to be in shape. Try it again after a week.