Hi! It is nice to see a new SML-themed episode, because I am always on the look out for those since the release of the SML NPC pack a while ago. I have not played much yet but I wanted to point out some observations and criticism that you may find useful:
1) In my opinion, the dialogue seems a bit too verbose. I don't think Tatanga needs to be this talkative or ambiguous in the opening, I feel like the exposition could be toned down slightly. I do like Luigi ducking out of the way of the energy beam, though.
2) This is much worse in the Toad village, where I personally think the "quest" to talk to the various village chiefs is frankly a waste of time. There is no challenge presented while doing so, it's *just* going through various houses, talking to people, going back, talking to them again, until finally you're done. I think this part could be skipped.
3) In that same level, I think you ought to remove the camera panning once you get to the burning village section, because it is a bit buggy. For one thing, the hammer bro and boomerang bro begin attacking even before the camera has finished panning (while everyone else is frozen) which looks quite a bit odd, but even worse, one of the flying blue koopas that beelines towards you can get off-screen, thus rendering the level unfinishable as you need to defeat all the enemies to proceed. Your choice here is to either improve the scripts to remove all edge cases, but I really don't think the level benefits from having these camera pans so by just getting rid of them you'd solve these bugs and the level would be no worse off.
4) One issue I have with the episode thus far is that the audio balance is a bit off. Some of the music tunes are very loud, and others very quiet. I don't think the burning village needed a bombastic metal slug theme for it, it felt a bit out of place. The worst example though is the bonus exit for each zone, which has a pretty loud SM64 theme before you pick up the sphere, only to transition into a very quiet theme (from SWMCP2 I believe?) once you pick it up. Volume balancing would do wonders here.
5) In the second castle level, there is some issue with the firebars getting behind the lava background graphics:
https://i.imgur.com/g9disp0.png
6) The reserve item (the powerup you store and can retrieve with the select button) can be activated even on the world map, which is obviously a bug.
7) I would make it so that locked doors have a visible lock on them, instead of having to get near them to be able to tell whether they're locked at all and waiting for the exclamation mark to show up or message window to appear and then close if you accidentally press up. Saves time and is clearer.
This is less of a complaint and more of a general observation, but truth be told, I'm not so sure making the first few levels in a Birabuto adventure feel nothing like SML was the best call here. I mean, the custom graphics look nice, but the first four levels (that is, grassland, mine, and castle) are quite mediocre and feel like filler to be honest. The level right after the first castle felt a bit better so I'm sure quality is only going to go up from here, but still.. I don't know, the way I see it, those levels are fat that could be trimmed altogether. But hey, your mod, your choice.
I realize my tone is a bit critical here, but I am still quite intrigued by this mod and will keep playing, I don't mean to shoot down the ideas on display here or force a course correction, just sharing my observations as a long time player in case they may be of use. Keep up the good work!
EDIT: more observations. The first level of birabuto is ok, and the second level is far better than what came before... I think the design is still mostly average but you're finally getting some good mileage out of the custom enemies here. The usage of honens, gaos and bunbuns was well done. The underwater area though leaves me a bit perplexed. I don't understand the over abundance of cheep cheeps, and especially the removal blocks.
https://i.imgur.com/UWC4Ojb.png here for example you can just wait for them to pass and explode, and the removal blocks even remove your superballs which feels bizarre. I would frankly rework this part by just having SML water enemies appear in it rather than these cheep cheeps and removal blocks. Additionally, it looks like honens are immune to superballs, I imagine this is unintentional?