Hey Solar, so I've played through much of the demo, and I've found a bunch of things I thought might be better to put into one post since most are pretty minor.

I couldn't play the game on my Mac machine, but I also have a Windows and Linux machine to try stuff on. I'm playing the game on Windows 7 on a gaming PC (so pretty good specs).

I'll split this post into three parts: the stuff I liked, bugs and suggestions

Stuff I liked

Eps controls great (although a little floaty for my taste). I like the music a lot, it goes really well with the art. The shaders are working great. The performance is good on my gaming PC, aside from the minor hiccups from when Java does a garbage collection (you might want to try gradual garbage collection if it doesn't slow down your game too much).

Bugs

1. When running from left to right or right to left with Eps, sometimes you can see the vertical tile seams. This happens in various areas in the demo (most prominently in the scrolling screen one screen to the right of the "fingerprint door" doors)
2. My game crashed after leaving it open (literally doing nothing) after like 20 minutes-ish? Have not been able to reproduce this one though
3. Not sure if this is a bug, but on the equipment screen there are a bunch of parts I have not gotten yet. More specifically the "shear legs", the "roundtable core", the "prescript 0-9-0 core" and the "deterrent arm", and I can equip all of them.
4. I pushed one of the runny/jumpy guys into another screen and it kind of just chilled there (they don't seem to come back into the same screen). That or he was just stuck on something lol
5. When I go fullscreen with an xbox controller, my xbox controller doesn't work anymore, I have to restart the game. Meaning, as of now, there is no way to play fullscreen with my joystick (since fullscreen doesn't stay active after a game restart)

1. When you talk to characters, it's not obvious to me who is talking (mostly referring to the cutscene with Twent and Jeremy). I know their mouths are moving and stuff, but it's too subtle for me while I'm reading the text. I really enjoyed the way you did it with the old Gearend (with the faces), but even just a "Jeremy:" or "Twent:" when one of them starts speaking would be helpful.
2. The fall right before Twent's room is not super obvious, but it's something I'd be watching out for as I play the game. I don't know if you intended that fall to be obvious or not.
3. When you speak to any character, Eps always moves to the right of them to speak to them, even if I'm way on the left. I think it'd be cool if it moved to the closest place (either to the right or left).
4. Transitioning between doors is too slow for my taste, it's almost like one second, I know it seems stupid but if you're going in/out of doors often, it's a little annoying.
5. Saving takes too long for me. I guess it doesn't matter if you don't intend for people to save a lot though.
6. Finally, if you're going for a more serious tone, all the characters are too light-hearted and fun. If you're going for a Cavestory type of feel, I'm not really getting it. However, this is only the demo, so I can't speak for the rest of the game. In case you're wondering, I really like the tone of the game as it is now.

I agree with suggestion 1

Bugs

1. Yeah, those seams are due to the tileset textures needing padding. I'll resolve that once I'm completely done with the game.

2. Hmm, that's strange. Can you tell me what OS it happened on? The crash logs will be captured in the game directory, in the .log files - if it happens again, it'd be super helpful if you could check those logs.

3. Yeah, that's intentional to give the demo player something to play around with.

4. Strange - gotta fix the behavior of those enemies to be less "finicky".

5. That's strange, full-screen shouldn't impact controller usage. Fullscreen has been fixed to remain after restarts, though.

Suggestions

1. Hmm, I see. I'll keep it in mind.

2. It wasn't not supposed to be obvious - it should've been readable. I'll have to darken the back tiles.

3. I'll keep that in mind, too.

4/5. I dunno, it's pretty rare that you perform these actions; I can shorten them, though.

6. The tone is, I think, what I'm going for (not very serious, but there's room for it here and there).

Thanks for playing!