Brain Surfing Level 50 Two kilograms of cotton or one kilogram of iron Which is heavy Answers. Brain Surfing is another puzzle game that breaks common sense by requiring ridiculous solutions for each of its levels. The game is amazing and super fun as it presents you with lots of funny situations where you have to make funny decisions. If you’ve ever played Brain Out or Brain Test and liked them, you should definitely give Brain Surfing a try. Keep in mind that the game is specifically designed to trick you so take into consideration taking advantage of everything including multiple taps, fliping/rotating your phone or even using your charger. Brain Surfing may go that far.