Thanks for the feedback!
Adding hints to challenges is a good idea. Some of them may indeed be too difficult early on. Were you able to complete the second challenge in the end?
What would you suggest to avoid the initial threat flaw pattern?
Since the central position is quite advantageous, I already restricted it for the first player. However, I have not found a good way yet to help a player recover from a disadvantage. Walls seem like an interesting direction.
Regarding the UI, the menu button is in the top right. I could make it more visible indeed.
And you can also play on a larger maps by tapping the gear icon on the top right of the new game screen