As of March 2022, Human: Fall Flat boasted of a total of 19 levels. The game developers have announced that they will be adding more levels in the future at no extra charges.
Certain levels such as Aztec, Ice, Forest and Water can be quite difficult, which only adds to the fun after you've gotten over the initial frustrations. After all, this is a puzzle game. It wouldn’t be very exciting if it were too easy to solve.
In the more difficult levels, it is helpful to have friends assisting you to tackle the challenges. Even if you are playing solo, do not lose heart and you should be able to finish all the levels.
There's no timer or single way to complete the challenges — you are only limited by your creativity. You could say that the game is more about the spectacle and having a good time with others, than racing through its fantastically minimalist puzzle maps.