You can find dark Digimon In other maps I believe. I tried the game on Windows and I was having a good time all the way until I evplve my Agumon to MetalTyrannomon. FarmIng Dragon/Machine exp was a bit hard but once you unlock other maps it kinda gets easier. Btw keep beating Digimon even if they don't drop the exp you want. I've noticed that causes more (and sometimes rarer) Digimon to spawn.