Pouring a cup of water seems to be an easy job for most people, but it is not the same situation for the visually impaired. They usually use finger to prevent from overfilling but this action is unhygienic and danger, especially with hot drinks.
Sun is designed for visually impaired people to help them to detect the water level when pouring water to prevent from overfilling. Balls attached in the handle act as a detector to detect the water level. They will rise when water are poured into Sun then touch the user's thumb to let them notice the cup is going to be full. Also, bright and contrast colours allow partially impaired people to figure out the level of the balls.