I was just made of aware of an issue with the game: some letters that increase difficulty or change gameplay are not being shown or applied properly.
The affected changes (as far as I know):
- Increasing island length to 6
- Increasing miner price based on income at the end of every wave
Both should be applied after 8 researches are unlocked.
The issue with this is that if you restart the game the gameplay changes will be applied but you will never be shown the letter, which is obviously very confusing.
I'm going to add a way to view your applied letters later tonight or tomorrow. In the meantime, if gameplay changes in some way after you close the game and restart it, know that this is the cause.
Apologies for any confusion.