Hello, thank you for your feedback. We're glad that you like our game. To answere your question - yes. It was a design decission to make the game hard. It's hard so that you have a challange, have a reason to play again and try other strattegy and so that winning is a big accomplishement that you can be proud of.
Limited amount of time played a role in making the game so hard but from the beggining we wanted it to be a challange.