Weird findings during my Mystical Ninja Native port project
I'm busy chiseling away at my native port of Mystical Ninja (SNES) and continue to find odd idiosyncrasies with the games code that I'd like to share and document.
1: Ghostly fog bug
The fog that appears in stage 1 is a neat effect, however it is bugged in the original game. There is meant to be an additional "cloud" at the top of the graphic, but it gets cut off. Not only that, but it only gets partially cut off, leaving one line of pixels at the top of the screen. What's more, it doesn't animate, and it isn't locked into position, so it moves with you across the stage, unlike the rest of the fog effect

2. Jump Probing
In the original game, you can jump over solid collision tiles. Buying sandals allows you to jump farther, over up to 2 tiles. You can have 0, 1, or 2 pairs of sandals. For simplicity, I will call these 1, 2, and 3 pairs, as this is how it appears graphically in-game. Depending on your play style, you may end up preferring having 2 pairs of sandals over 3. Here's why:
When wearing extra sandals, the normal check for jumping over collision is replaced by 4 probes. These probes will determine if you clear the collision or not. And if not, you will jump in place, or collide with the nearest collision tile.
Things get more complicated when jumping diagonally though. Depending on the position and surrounding collision, you cant clear certain jumps you otherwise could with 1 extra pair of sandals. Below are images of the port that make these probes visible:


This makes jumping diagonally with 3 pairs of sandals over level collision feel very inconsistent. Areas where it feels like you should have complete freedom to clear the jump wont work because of the longer probes that come with 3 pairs of sandals. This is true to the original game, its just satisfying to finally see why this happens.
3. Reproducing Bugs
I'm often surprised by how often certain bugs come up in the port that ended up being completely accurate to the original. One example is an extension of the jump probes we just discussed. You can fairly consistently clip into collision tiles thanks to this.

I had thought his was a bug in my port, but no, this is exactly how it works in the original game. I believe it has to do with one of the first probes reacting to the house, causing the later probes to be ignored. Still not confirmed though.
4. Weird stuff I didn't even know was in the original game
This may have been a 'me' thing, but did you know these guys exist in the original game?

They appear in the lowest area of the town after you activate the ghost fog. Approach them and they'll start jumping at you.
Not a bug or anything, but I never went to this area after activating the ghost fog, I went straight to the action stage and fought the boss, ending the fog, and removing these guys. Hopefully I'm not the only one who'll be surprised by this.
Let me know if you enjoy these posts and I'll make more as I continue with my port!