Ruby Wolf

One of the things that can easily bring a Gameboy to its knees is having a tile map. Just having one. You're used to just making maps of any size you want and it'll work. Just make an array of bytes and use that to draw the tile map. On the Gameboy this becomes an impressive feat.

You get two sheets of 128x64 pixels you can combine for a maximum of 256 patterns. That doesn't sound as bad until you realize the upper sheet is shared with sprites and you have to also leave some for the system (windows, text, information, etc.). A lot of games would put the environment-specific patterns in one of these sheets, like Pokemon Red/Blue or Links Awakening:




So I drew some patterns that look like they're from Ruby Wolf. Each cell is a 4-color image and the colors here are just for reference. These colors are either just the 4 shades of grey or are actual colors from one of 8 palettes on the color system. I'm doing a dual mode game which is in color, but will work in the older system without it.



I've called these patterns instead of tiles. You cant just fit a sheet of tiles on an image like you're used to, there's no room. If we did that here, we'd only have 32 tiles. What we do is combine these patterns to make tiles, 4 patterns to a tile (some of the tiles aren't used yet, I marked them with purple to remind me). I've also made it so the tileset editor displays things closer to what an actual Gameboy Color system would actually show, it mixes colors oddly.



Games on many of the old console systems would go up to 256 tiles, I'm splitting mine into two groups of 128 tiles with the second set being tiles common for the entire game (item boxes, etc.). Tilesets also encode the collision and other flags with the patterns. The encoding I came up with uses 6 bytes per tile. This means it occupies 1536 bytes when unpacked so I've used up a little more than 1KB already. The Gameboy only has 8KB of RAM for you to use. If you made every tile on the screen a 1 byte reference, a 32x32 map takes up another 1KB and even larger maps like a 64x64 one would take up 4KB. You still need to leave room for your algorithms, objects, and the rest of the game engine!



There is video RAM. You can fit 16x16 tiles on the background map there which is even smaller. Some games simply do this, most notably Links Awakening where the action always takes place on one screen and it scrolls new ones in when you change areas.



If I don't want to waste the rest of my RAM and I don't want to squish maps onto single screens, then some sort of streaming system has to be made.

I found a good answer from a NES game, the original Final Fantasy. It encoded its large map as 256 tile stripes and would decode them into rows to look them up.

https://datacrystal.romhacking.net/wiki/Final_Fantasy:World_map_data

The scrolling window wraps around the background map if you go over the edge, so all you have to do is place new tiles as you move.



To test everything, I drew a quick amateurish hallway-room-hallway map that's 32x32 big (twice as big as what fits on the background) and encoded it as 32 stripes of 32 tiles each.



We're not done yet! I had to actually program this using LR35902 (Z80 like) machine code instructions. It runs at about 4.19Mhz and the fastest instructions take 4 cycles so at best you're getting a million cycles a second. The system runs at (basically) 60hz (close enough) so this means you get about 17 thousand fast instructions. You will run out of time easily if you're not efficient.

In an RPG like this, you move on tiles. This means there's only 2 of the 16 frames you're walking where new map cells & tiles have to be loaded. Every time this happens, the system loads either 1 row from the map (if moving up or down) or 10 rows from the map (if moving left or right). It has to decode 10 strips and grab a single tile out of each one for left and right movement. You can't just encode the map in columns and add it to the data because then the result is larger than uncompressed, defeating the purpose.

I've somehow managed to make left and right movement fit in time with half the remaining frame to spare (BGB has a handy load indicator if you use low power CPU waits at the end of each frame). This means limits the width of the map to about 64 tiles because the decoding algorithm scales linearly with time. If you run out of time it makes everything jitter noticeably as you walk. I might have to do better in the future if I find 64 tiles wide isn't big enough, but for now I've got maps working. The answer will always be to get more creative..




Or you can open RPG Maker, scribble tiles on a map and hit play.

Its been a while, I've been plenty busy, but I haven't forgotten about this little game. After some consideration, I've decided the return of this game should be developed for the Gameboy. After all, its the kind of style I went for when I wrote this game demo. The game will continue to be a simple treasure-hunting dungeon-crawling RPG, a task fit for the system.

I'm creating a dual mode ROM which means it will work in the original Gameboy, but also work and use colors on the Gameboy Color. Link's Awakening DX and Pokemon Gold are good examples of dual mode Gameboy games. They typically came in the black cartridges instead of the clear ones. Its impressive that there could exist a handheld game that would play in the 1989 Gameboy but also work in a 2003 Gameboy Advance SP. Even beyond that, there exist emulators for mobile devices, perfect for playing non-action games.

I've just finished a Sharp LR35902 assembler and have had successful tests getting things to work. There may even be a few tricks I can do with the sprites to increase the number of colors per character, but we'll see if they actually work. I can't really say when I'll get a chance to work on this again, I do have a more important game to finish, but I'll definitely look forward to it sometime.

DarkFox and I will continue this game as a new game entirely (with the same kind of gameplay). It will be GBA-themed instead of GameGear. Stay tuned for updates.

The game (demo) is missing lots of things, title screen, introduction, instructions, etc.

Here's a quick guide.

Enemies are always visible on the map and move when you do. If you keep moving and don't stop, you'll move faster than most enemies. Once you defeat an enemy, it is gone for good, it will never respawn if you leave and come back. You should avoid fights with enemies you don't know you can easily defeat. Once you can, you should hunt them all down to gain EXP. Even a single level gained can make a difference.

Avoid fights even if you feel you're on equal ground. You cannot heal during battle, ever, you don't regenerate health or energy, and if you escape, the enemy is fully restored. You really should only ever escape if you didn't mean to start a battle. You're faster than most enemies in the game, it will almost always work.. But if you're not, there's only a 10% or 30% chance it will.

You don't regenerate health or energy, you cannot grind, and there are no shops. You have to save and use what you can find inside. This requires some strategy, especially when you reach the area where almost everything keeps poisoning you. In that case, you should only use a remedy when you don't think you won't just get poisoned again, but you can't hold off too much since it never goes away and damages you per step.

You'll keep finding yellow item boxes full of treasure. This will increase your score. You don't have to get any of them to complete the game, but you won't get a good ending if Sofia leaves the ruins empty-handed. Strike a balance between how much risk you want to take. Getting 100% completion will be an accomplishment.

The blue item boxes always have equipment inside. You probably need many of these to complete the game or you'll be too weak. As you collect a lot of equipment, you'll notice you can sort of customize Sofia's stats with different combinations of equipment. Try to always go for these.

Every boss in the game will be optional (except for one). You can just walk right by them. Of course, you really want to power up and then take them on. Each boss is loaded up with gear that they'll fight you with. They also have five times the amount of health and energy they normally would. Remembering that you cannot heal during battle, be sure you can last that long. If you can defeat a boss, you get to take all their stuff. There's always going to be at least one piece of exotic or better equipment on them. So with every boss you defeat, the game gets easier for a bit. There's only one to fight in the demo so far.

This game is really tough on you and throws away all the JRPG tropes that made these kinds of games too easy (grinding weak enemies, buying 99 potions, etc.), but I do let you save anywhere from the menu. Do it. Save often. Don't save yourself into a corner though. If you like to save too often, try using up the other save slots. They'll get descriptive names, statues, etc. later. Since there is no game over sequence written yet, the engine suddenly closes after you die. Game over. You're dead. You'll have to load a previous save to continue.