4X4 should probably be renamed endless. It's not really that difficult to survive basically indefinitely, it seems to me. You gotta balance ultimate usage for Springsea Water buffing between mana generation and weapon generation, but since one-hit-kills still lose you only 1 attack at higher difficulty levels and since Obsidius's retaliation is blockable and the dude with the ranged attack never gets more than 1 attack unless you let the enemies buff him via death it seems like you can continue on at least far further than my patience and the lack of a save function allow, if not indefinitely.