Yes, automatic generation is a complicated problem. There is a lot of theory about it and the most adept of the subject could be stressed with this naive suggestion but the first thing that comes to mind is reversing the problem. Nomally you design a level and the player must select the best way to go. But in the automatic generation you could generate a random path for the player and then build the level around this path. Preventing the walls from crossing the path and with a tree at each point of the path to ensure that the player can follow it. This would help to create the infinite mode and also as a guide to generate the levels of the game (you generate many automatically and choose the best and make improvements). Good luck