Also: You can kill the nightmare guy buy dashing into walls to get the temporary invincibility (Flashing Character), then standing near him so that the meteors land on him. When he is hit by meteors he drops black gems you have to pick up. Pick up enough and he dies. Good luck :D
(You keep all of your skills from the previous day if you can defeat him)
A couple of tips for the more hard to find things: Talk to the robot that gives you the hardy skill 3 times after recieving the skill for a codex. After getting double jump and dash you can run dash off the very top of the structure to the right of the robot town for a hidden blue gem and a handful of red gems. Took me forever to figure out where they were. Hope this helps.
Game is too buggy to play. Was good, and I hate that I wasted so much of my time on it, but being stuck in darkness indefinitely is just ridiculous. Tempted to rate low but will withhold to wait for an update to fix darkness.
Best way I've found is put all of your points into attack>Defense>Agility>Speed and whatever you have left put into experience. As you level keep maxing out the four stats as fast as possible. Then just swarm over the other guy. Ridiculous how easy it is this way. I can win with all the exp multipliers on at the same time with ease.
What I did btw for defeating the last boss is after conquering about half of the map began to just create the things for green giants. By the time the aliens came out I had an army of 25 giants to steam roll them with. Was kind of tricky though because they attack you from 4 directions :/
Game needs badges :D
I beat the alien boss, but saved it right before I did the first alien battle in hopes of a "Hard" badge for killing the aliens later. Crossing fingers...