The only invisible walls of the game are when you're trying to get out of the world... No game lets you out of the world...
If I remember the Revenge of the Nora quest properly (I could be thinking of another quest), you hit that respawn machine, but this is the only one.
I honestly don't know what invisible walls you're talking about though. I've literally ran up some mountains by just constantly jumping. You can get to any part of the map, assuming it's not outside the play area.
Save money to buy the purple travel bag, it gives you unlimited fast travel. The game also has a lot of camp sites so travelling is no issue. You don't even have to touch a camp site, just being near it activates it for fast travel.
Fighting humans are lame, I'll agree, but the robot fights are well done. There's a lot of weapons you can buy that opens up different strategies. The fights get pretty varied too depending on what strengths and weaknesses an enemy has. Also trying to hit those target points with the right weapon is fun and rewarding.
