Honestly the most impactful (in my opinion) would be the most casual things such as:
main menu
win/loss screen
options with difficulty, saving highscore, volume
possibly some balance changes in spawning rate from towers and villages - i won like 2 times by spamming traps in danger and just throwing people in altar
you could play your game in weird ways and see if it works - if it does, then you should somehow fix it 😅🤔
Good luck with next projects!