Stage 4... it's pretty big! Until the very end when you ride off with Avior, the map is one large connected piece. My original plan with the forest area was to have the platforms be directly linked to the trees in the background, but that would've been a tremendous pain to design, so they just float in the air now.
The stage was initially going to start off with you running from the beach to the base entrance, getting scuba gear, then returning to the first beach, but via a different, tree-top based route. Once I thought of having Mizar chase you through part of the forest though, I ditched the original backtracking idea and made that part more straight forward.
The first part of the stage where you go over the large tree is a very subtle and pointless throwback to the first MikeMan game.
The second part of the forest was specifically designed for the Mizar chase that would take place there later. The part at the top of the waterfall was supposed to be a bridge, but placing enemies there was kind of awkward so I ditched that, so there are just a few planks there instead.
The base area is interesting because a lot of the original ideas for it ended up in stage 6, and stage 6 ideas ended up being used here. Before Stage 6 was really anything, my initial vision for it was having you start by an elevator, and collecting 3 keys to access it. This eventually turned into the quest to recollect your weapons, and the fight with Mizar on the elevator, while stage 4 borrowed the core idea more directly.
On the flip side, the stage 4 base idea was initially a much more closed space, narrow area, that would have you trying to stealth by enemies rather than fight them. Of course if Carina kept her weapons, this wouldn't have worked at all. There are a few enemies here that don't react until they see or hear you, but there's no reason to try and avoid them. In the end I brought this idea back briefly when playing as Avior, avoiding enemies rather than fight them was a much more natural fit for him.
The underground wasn't really going to be it's own area at first. It was just going to be a gradual fade as you got deeper into the hunters base, the metal guarding would stop and it would become a cave level, then a lava level just before the boss. But like always, a very small idea got blown up to a huge thing by the end.
The second idea for this area was to make it a bit more open, with different loops through it. The first path would end with you getting the wall-jump boots as an item, then that would allow you to go back to the start, and progress a different way to the boss. I felt having you get an item this way would be weird though, and just had Saiph give you the wall jump boots instead.
This area was originally much different than in the final version. I hated the original though, there were frequent spots of enemies not being able to attack you at all, and didn't really play to the strength of the rock enemies at all. The new version is tougher, and also allows a lot more freedom since it isn't so cramped.
The ocean segment was a lot of fun, but tricky to keep fair for the player, since the area Carina has to move on is extremely limited. This was initially going to be a scene similar to the snow chase at the very start of stage 2, but changed it to keep things fresh. Code wise they are almost exactly the same, except for how Carina acts.
Another unintended but interesting thing about Stage 4, it reminds me of the chinese elements: Wood, Water, Earth, Metal, and Fire. As an added bonus the very last part takes place in the sky. I ended up hitting every element with this stage!
Even though it's very difficult to notice, there actually is a difference between the green and red versions of these guys. The green ones will stop an attack if you push them back, but the red ones will keep going, so you really don't want to get close to them. As another large enemy they were pretty hard to place in good spots. My favorite usage of them is in hard mode in the caves, where they walk around in the lava below you, so you are able to jump the claw attack even if they're close.
The flies are an intentionally annoying enemy, I wanted something that would bunch up so that when you got the shotgun a bit later on, would show off the multiple-hit capabilities it has.
Of all the larger enemies, these guys are probably my favorite. They demand your total attention, and can really mess you up if you aren't careful. Being able to jump over them probably helps a lot as well, you can choose to attack them, or just fake them out and run away.
Saiph when you meet him the first time. At first I felt this boss was too similar to Draco in design, since they both do a combination of random attacks from the air and ground, but in practice, they don't feel that similar to me.
The clam boss is easily one of my favorites in the entire game. Shooting the bullets allowed for a much more dynamic fight that is never quite the same twice.
The second fight with Saiph. I didn't really intend for him to come back a second time, but figured this area could use a boss, and he was available. Tying the wall jump boots to him was a lucky coincidence really.
This guy was fun because I didn't have to bother drawing the actual animal forms he takes, just vague outlines. Getting the lava effect to work and be smooth between all of the forms was just as much of a pain though. The boss is actually a mask on top of the stone wall, and the lava effect is the lowest layer behind everything.
Having a boss chase you from the background was something I wanted to work into Project Inthri 3, but could never find a really appropriate place to do it.
Rough sketch. The missiles were going to shoot from the wings instead of from behind like they do now.
The way the missiles act was changed shortly before release of the game. Originally they were just a set pattern that vaguely homed in on you, with a chance for the third one to hit Mizar. Now they are all dynamic and can hit her, so her life bar was changed from 2 hits to 6.
Stage 4 had one of the most annoying bugs, a single frame loophole with the wall jump. Normally the wall jump asks you to press towards the wall, then when you jump, turns Carina the opposite direction and removes player input for a split second. If you pressed away from the wall on the exact same frame that you jumped though, Carina would turn around a second time, and simply wall jump back towards the wall, resulting in her going straight up.
I had thought I fixed this bug early on, but it ended up coming back right at the end of development, along with a new friend, jumping through certain ceilings due to another huge oversight in the stage 4 code. I'm using a keyboard macro here to do perfect turn+wall jumps. I'm pretty sure I managed to fix both bugs once and for all this time though.