Guxt Modding Notes

In *.pxeve files:
Note that I've only checked this stuff for map1.pxeve!
First byte does something. Upto 0x3B gives blue background with title screen BGM, 0x3C gives blue background with Stage 1 BGM, 0x3D gives empty level with blue BG and clouds, 0x3E to 0x5F give a normal level but something going on with the bonuses. Some values stop the Ikachan bonus from ever appearing. 0x60 and onwards (I think, there may be other stuff more later on) result in a black empty level with title screen BGM.

The second byte should be less than 0x7F, otherwise the level will just be a total empty blank. It is 0x01 default. Also, there is a 0x01 at offsets 0x01, 0x06, 0x0B, etc. that all don't seem to do anything except as said above. They may be separators between NPCs, for all I know.
Actually, that's only the case with event1.pxeve. Other event files have other values in those bytes, meaning it is most probably a part of the NPC code which I haven't figured out yet.

After that, apart from aforementioned unknown NPC variables, NPCs take 4 bytes to encode.

The first byte describes horizontal position. The screen is 16 units wide, so 0x00 to 0x0F is all you need here.

The second byte specifies something about when the NPC will appear. Time? Vertical position? Higher value means quicker it will appear. There's a limit after which the level just becomes a total empty blank.

The third byte specifies the type of NPC:

0x3C are power-ups simply contained in a harmless box, 0x3D are power-ups simply floating without any coating/case, 0x07 are like 0x3D floating downwards faster, 0x40 are power-ups contained in an enemy, 0x4A is an invisible thing that floats downwards and you can shoot it to reveal a power-up, 0x4B is an asteroid with a face which reveals a power-up upon destroying. These are one of the few NPCs that use the fourth byte, where it specifies which kind of power-up:
	0x00 shows a 'P' but becomes empty on shooting it, and when obtained, it turns you almost invisible and you can't shoot.
	0x01 is the Speed power-up.
	0x02 is the Shield.
	0x03 is the Twin bullet.
	0x04 is the Machine Gun.
	0x05 is the Triangle.
	0x06 is the Rear.
	0x07 is the Wide.
	0x08 is the 3 Way.
	0x09 is the Star.
	0x0A is the Harpoon.
	0x0B is the Anchor.
	0x0C is the Rocket. (An unused, Missile-launcher sort of thing.)
	0x0D is the W.M.Gun. (Wide Machine Gun?)
	0x0E is again that 0x00 thing. So, there are 13 power-ups in all.

0x2D are bonus items, specified by the value in the fourth byte again.
	0x00 is an Ikachan.
	0x01 is an arrow, like the ones from Azarashi.
	0x02 onwards it seems to be nothing, but it probably has something to do with the first byte of the file. Probably not a tileset problem as there's a separate bonus.pximg file.

0x00 to 0x04, 0x06, 0x0A, 0x0D, 0x0E, 0x13, 0x1C, 0x1D, 0x25, 0x26, 0x2E, 02F, 0x55, 0x56, 0x57, 0x5B, 0x5C, 0x5D, 0x60, 0x62, 0x69, 0x6A, 0x6B, 0x73, 0x74, 0x75, 0x78, 0x79 are nothing. (They might have been invisible stuff or stuff I didn't notice, so you might want to check it out later for yourself. For example, I was almost going to put NPCs 0x36, 0x38 and 0x4A here!)

0x0C, 0x10, 0x11, 0x21, 0x22, 0x24, 0x32, 0x33, 0x34, 0x35, 0x37, 0x39, 0x47, 0x4D, 0x4E, 0x4F, 0x50, 0x59, 0x5F, 0x67, 0x6D, 0x6E, 0x70, 0x71 crash the game before you see it. No idea what they're supposed to be.

0x3B are those basic enemies that come in the very beginning.
0x05 are the second kind of enemy you see, the thing where one 0x3B comes out after you shoot it once.0x08 are the little slow jellyfish-like-floating things that come in great numbers near the Stage 1 checkpoint.
0x09 are those circling things that come a lot for once near the Stage 1 checkpoint.
0x0B are those largish things after the checkpoint in Stage 1, which periodically shoot three bullets upwards.
0x0F is the Stage 1 boss! I don't know how in the real game the Boss' death is linked to advancing the stage, but whatever.
0x12 makes this little white bullet-like thing appear that sticks to the screen, doesn't move, and kills you if you touch it.
0x14 is a large asteroid.
0x15 is a tiny asteroid.
0x16 deletes all NPCs, making the map blank, apart from the background/tiles.
0x17 is a tiny asteroid that drifts around. 0x00 slow left, 0x01 slow right, 0x02 fast left, 0x03 fast right, 0x04 onwards straight down.
0x18 is a version of 0x3B that slowly oscillates sideways.
0x19 is a version of 0x05 that shoots red bullets.
0x1A are those asteroids propelled by some enemy.
0x1B is an asteroid stuck to the top of the screen.
0x1E are the very large square things in Stage 2 that occasionally shoot.
0x1F is that enemy that comes once before the checkpoint in Stage 1.
0x20 is the Stage 2 boss!
0x23 is a single missile projectile.
0x27 are the large square enemies from Stage 3 that explode into a ring of many red bullets when killed.
0x28 are the small things from Stage 3 that remain stuck in their position and periodically fire three red bullets.
0x29 are the square eye things from Stage 3. In the fourth byte, 0x00 makes it permanently dormant while 0x01 makes it open its eye after a while.
0x2A are the eye things from Stage 3 that slide along a horizontal axis and after a while open their eye and periodically fire a red bullet.
0x2B are the little bird/fish things from Stage 3, the ones that come from the top left, curve around beneath you, and exit from the top right.
0x2C are the small eyeball things in Stage 3 that roam around and keep opening/closing their eye and are invincible when their eye is closed.0x30 are the eye things from Stage 3 that turn around to the opp. direction when shot, open their eye, and then periodically fire. Using 0x00, 0x01, 0x02, 0x03 in the fourth byte of the NPC set its default dormant position to left, up, right, down respectively.
0x31 is the Stage 3 boss!
0x36 is an invisible box that blocks bullets, and moves downwards like most enemies.
0x38 is a checkpoint!
0x3A are those tiny things that start appearing midway through the Stage 3 boss, they move down on those train-tracks at the side of the level and fire at you sometimes.
0x41 are those dark blue ripple things in Stage 4 that seem like they're travelling underwater, and after they reach the top of the screen they turn into a generic enemy that sometimes shoots.
0x42 are the enemies from the game's icon.
0x43 are the sideways-moving train-like things that occasionally shoot, from Stage 4.
0x44 are the metal grate-like things that KEEP SHOOTING AT YOU. In fourth byte, 0x00 keeps them dormant, 0x01 means they open up sometime to shoot.
0x45 are the small eyeball things from Stage 4 that don't move, stay dormant and just before dying they open their eye and fire red bullets.
0x46 are the things that stay in their position but swing this large ball on a string around in circles.
0x48 are also little bird/fish things, but these ones make a few small circles near the screen's top, then home in on you.
0x49 are a tight ring of four 0x48s.
0x4C is the Stage 4 boss!
0x51 are the little things from Stage 2 that crawl a bit towards you, pause, then crawl a bit again, etc. They come right after the checkpoint.
0x53 is this white sphere that just stays stuck there and does nothing except killing on contact.
0x54 are first enemies of Stage 5, the white squares with a gray slit through them. The fourth byte tells how far from top of screen they'll appear.
0x58 are those octagonal things from Stage 5 that periodically fire a bunch of little missiles.
0x5A is a single small missile.
0x5E are the briefcase-like things that leave behind a corpse when killed.
0x61 is a simple square brick that doesn't kill you when you touch it, and you can shoot and destroy it. It's not solid, like a background tile.
0x63 are the non-shootable things that keep firing red squares at you. In fourth byte, 0x00 keeps it dormant and 0x01 makes it active.
0x64 is the lower part of the Stage 5 boss.
0x65 is a single eyeball that looks like it's suposed to be part of a boss. When it opens its eye, the game crashes. I guess there are special rules	on how to use it or something.
0x66 is a double-bubble projectile from the Stage 5 boss. It starts from its origin as specified in first byte. The fourth byte tells the angle of trajectory, in a clockwise direction. 0x00 means it goes straight to the right, 0x20 makes it go in a 45 degree diagonal to the lower right, 0x40 means it goes straight down, and so on.
0x68 is a long ribbon-like streak of light that follows the same angle values as 0x66.
0x6C is a circular boss with red eyes.
0x6F is a single red laser.
0x72 is a single reddish whitish bullet that simply moves to the lower right. You can't control its trajectory.
0x76 forcibly sets the map's tileset to that of the Nth stage in Guxt, where N = <value in fourth NPC byte> + 1. So 'XX XX 76 02' sets the current map's tileset to the tileset of Stage 3.
0x77 pans a picture of an enemy/boss across the screen. The fourth byte specifies which. 0x00 to 0x05 are the six bosses, and use the 'enemy6.pximg' NPC tileset. Values of more than 0x05 show various enemies, and it uses various different NPC tilesets for displaying enemies from different stages. Perhaps the 0x76 NPC was made for this purpose, to be used in the credits? I should probably look into details for the values of more than 0x05. Or does someone want to pick it up from here?

That's all. 0x7A to 0x7F crash the game, and values above 0x80 just turn the level into an empty void with no enemies or background or anything.
Have fun!