Just beat my first run, and I really like this project and think it's a really great CS mod overall, and definitely worth praising! Although, I do have a few issues with it. Apologies for the list being long, I'm a game design nerd who likes to think about game design a lot.
1. The levels are much too large, and having to go around the entire thing collecting every single star gets exhausting, and makes runs take way longer than I feel like they should. I know I can exit the level after collecting half, but tell that to the max health bonus you're crippling your run by not taking. I'd prefer if the health bonus were moved to its own pickup, and if the remaining stars disappeared when you got all 10 you need. Even just options to change the level size beyond pure randomization would go a long way.
2. There are 2 options for the map, and while both are great, both have major downsides that make it somewhat frustrating. The default map is a good size and lets you see the whole level at once, which is a godsend for finding stars and pickups, but if the randomized map size option generates too large, then a chunk of the level will be offscreen. On the other hand, the tweaked map is very nice and pretty, but not being able to zoom out to see the whole level makes it functionally a downgrade.
3. Adding roguelike elements to Cave Story is a great idea, but I feel like it falls short on the "player choice" department. One of the major selling points for roguelikes is the choices you make which ultimately affect your build. The crafting system is a great example of this, although it appears far too infrequently to feel impactful, and the choices are few enough that you'll basically always know exactly what you want, at least in my experience. Other roguelikes commonly have stuff like shops or multiple choice item sources. If every level had at least 1 chest which allowed me to choose between 3 items, that would make those choices feel impactful, and let the player strategize more. Or better yet, maybe every chest throughout the game could offer 2 items, and you have to pick one to take?
4. Navigation of the environments feels a bit unsatisfying. Since all the levels are super big and open, and you can only see a small area around you, it feels like I'm always gambling with whether there will be something above or below me. The destructible environment makes it feel like a bandaid fix for an incomplete level generation algorithm, just to make sure you don't get stuck. But ultimately, the game turns into Minecraft block pillaring simulator. I would love if the maps consisted of shorter, wider rooms so that everything felt more cohesive. Maybe a dungeon crawler inspired "randomly connected prebuilt rooms" system taking inspiration from base CS, other 2D roguelikes, and various other "metroidvania" games would eliminate a lot of the frustration? Not to mention spikes are WAY too prevalent, and having to swap to the polar star (or take unavoidable damage when falling) can be rather tedious. Part of me might also wish that this game had double pickups & danger but halved length, so exploring the levels felt more substantial, instead of it feeling like you go a long time without getting anything. Basically just cutting out odd-numbered levels for better pacing.
5. Maximizing the window has a few bugs, first of all being that the character select disappears if you do it while on that screen. Also the whimsical star still expects the game's original resolution, so it'll be further down and to the right than where your cursor actually is.
Besides all of that, though, there's a good number of things I really like, and which I'm very impressed by!
1. Even just an overhaul mod of this caliber is really impressive to be able to put together, and it deserves praise on that front alone!
2. The item variety is really cool, and the item sprites look amazing!
3. The design of the new weapons & weapon upgrades is really nice, I never thought a melee weapon would work so well here, and the upgrade for the machine gun is fantastic! The whimsical star is really fun to use, too! Only way it could be cooler would be if there were more ways to control it, but even just being able to play "laser pointer adventure" with the thing is really fun!
4. I'm impressed by the large selection of characters and gameplay modifiers!
All in all, this is a really cool mod, and I'll definitely be playing more! Now that I've managed to win a run, I'll definitely be giving other characters and difficulties a shot!