I enjoyed this mod very thoroughly.
For a first release, this mod has an incredible amount of polished content. I absolutely love the atmosphere of this mod. The 60 fps hack, music, and level design all together set a very fresh tone that you don't normally feel when playing a Cave Story mod. The sound effects were really cool sounding as well. As far as the art and music goes, my only complaint might be that it seems like it would have been fitting to have different "Get Heart Tank!" and "Got Item!" music, because the original counterparts don't fit very well with your customized look and feel. About 20 minutes in, I realized that the aspect ratio is 16:9, which is totally awesome, because that would make it fit with most screens these days. Much to my disappointment, the full screen feature doesn't seem to quite work, no matter what I try with DouConfig. I really liked how you used familiar hacks in a way that didn't feel forced, and smoothly weaved in new hacks that we haven't seen much before; it was a huge breath of fresh air from most assembly gimmicks that exist simply to show that it can be done.
The level design overall was excellent, and the exploration was both intriguing and rewarding. I thought it was cool how you can choose different characters at the beginning with different abilities, but based on what I can tell, it seems like there's not much of a point in selecting anything other than the scout, given that the others don't have any substantial advantages (the closest one being to breathe under water, but that's insignificant next to more health and a booster). I could be mistaken on this, I didn't look into this too much. I sort of reached a dead end in my exploration after I beat the second boss (the shinier Balrog). All the unexplored territory was mostly doors that didn't have events assigned to them, which I'm assuming means I reached the end of this demo.
Even though I enjoyed this mod, there were some things that bothered me:
-Whenever having a chest for us to open, it's best to use a <PRI command to pause the game instead of a <KEY command, because with the latter, enemies can get to you while you're reading the text boxes.
-Minor typo with the text box here:
-That first balrog-like boss was pretty epic, and the music and flow of it was really cool, but it was very poorly balanced, full of fake difficulty, and frequently causes the player to rely on luck. Giving the gun limited ammo down to 5 was a cool part of this mod (as was the quarduple firing if it doesn't hit a wall), but I think that the player gets nerfed just a little bit too much. Shooting away all of the projectiles emitted by the boss and not getting killed requires some extremely precise strategy that doesn't so much require skills and reflexes as it requires developing a boring and tedious strategy that abuses the boss' fight patterns. The end of the second phase is pretty much impossible to power through without getting killed unless you have your gun still at level 3 and the boss just so happens to be at the far end of the room such that you're not immediately cornered. I also think the 3rd phase (the Pooh Black resprite) is not very well balanced with your health. Dodging those projectiles when the boss is about to descend often depends on luck more than reflexes. Perhaps others will disagree with me, but this made me come close to losing interest in this mod, and I ended up modding the game to get through this part.
Overall, you did a really good job on this mod, and definitely put a lot of time into working out most of the bugs. I hope to be able to play the next release.