The difficulties didn't take much time at all. It was just a few lines of code to set the difficulty to playerprefs and then retrieve it in the game and change the timer accordingly. So it was only like 5 mins or so to implement. However, I think adding the endless mode was not a good idea because I didn't have time to playtest and bugfix it. I playtested it after the jam was over and the respawning didn't work after a score of 20 or so. Oh well. Thanks for the feedback!