Well, what can I say? It's difficult for me. At least in comparison to MUSHA which I can beat. Of course, I've never been great at shoot 'em ups. I love them, but I'm average at best.
As far as what I meant by unintuitive, perhaps that wasn't the best choice of words, but it's difficult to explain. As I move my character around in 'MUSHA,' it feels effortless, as though I have complete control. While in 'Robo' there is always a slight delay in my movement, a sluggishness. I think this is mainly due to the way that they designed the character's sprite movement, in that when you move in a direction, before you begin to actually travel in that direction, the character adjusts itself. It's like a shift of the robot. Again, it's difficult to explain, but when you play it you should be able to understand what I mean. In 'MUSHA' when I press the d-pad the character immediately moves whereas there is a short delay in 'Robo.'
Technically speaking though, 'Robo Aleste' takes place in feudal Japan so the robot technology would not have been as advanced as it was in 'MUSHA' which is set in the future. So perhaps the slightly sluggish movement was a conscious choice by the developers in that regard. I don't know. Anyway, like I said before, I think it's a great game, I just prefer 'MUSHA.'
