Game Boy glossary

Retroable turns a sentence into a real ROM for the original Game Boy. These pages explain the words around that: the file, the screen, the cartridge, and the sentence you start from.

• ROM

  A Game Boy ROM is the whole game in one file, usually ending in .gb. The console runs that file and nothing else. Retroable's job is to hand you that file.

• Cartridge

  A Game Boy cartridge is the plastic shell the game lived in. It is about 57 by 65 by 8 millimetres, with the top-right corner cut so it only fits one way.

• Emulator

  An emulator is a program that pretends to be the Game Boy. The chip it imitates is a Sharp LR35902, running at about 4.19 MHz. Your ROM is the software that chip would have run.

• 160 by 144

  The original Game Boy screen is 160 pixels across and 144 pixels down. That is the entire picture. There is no larger resolution hiding behind it.

• Four shades

  The original screen does not show color. Each pixel is one of four shades, stored as a number from 0 to 3. Two bits are enough for that.

• GBDK

  GBDK is a C toolkit that compiles a program into a Game Boy ROM. Retroable's games are C, and GBDK is what turns that C into the .gb file.

• Memory bank

  The Game Boy CPU can see 32 kilobytes of the cartridge at once. Bigger games cut the ROM into banks and swap which bank is visible. That swap is the memory bank controller's job.

• SRAM save

  The Game Boy has no internal save for your progress. A game that remembers anything keeps it in RAM on the cartridge, often backed by a coin cell so it survives power off.

• Game Boy music

  The Game Boy has four sound voices, not a recording. Two play beeps of different shape, one plays a short wave you draw, and one plays noise. Songs are notes for those voices.

• D-pad

  The cross on the left of a Game Boy is four switches, not a joystick. Pressing it closes one or two of those switches. The game reads them as up, down, left, and right.

• Prompt

  The prompt is the sentence you type to describe the game. It is the brief. It is not the code, and it is not the ROM.

• Sketch

  A sketch is an optional picture you attach to the prompt. It shows the look you want. The Game Boy does not display that picture. It displays tiles.

• Edit

  An edit is one change you ask for after the game already exists. "Make the jump shorter" is one edit. A new game from a new sentence is not an edit.

• Public game

  A finished Retroable game is public until you say otherwise. Its page is at retroable.dev/g/ and anyone can play it. The page includes the prompt and the sketch.

• Original Game Boy

  The original Game Boy is the 1989 handheld, the DMG. Retroable builds ROMs for that machine, and a separate Color ROM when you pick Game Boy Color. Advance, NES, SNES, Game Gear, and Mega Drive are in development.

• Sprite

  A sprite is a small picture the Game Boy can move independently of the background. Hardware sprites are 8 by 8 pixels, or 8 by 16. The machine allows 40 on screen and only 10 on a single horizontal line.

• Tile

  A tile is an 8 by 8 block of pixels, and it is the brick backgrounds are built from. Each tile takes 16 bytes, because every pixel is two bits.

• Flash cartridge

  A flash cartridge is a blank you can rewrite. You copy a .gb file onto it, put it in a Game Boy, and play. When you want a different game, you copy a different file.

• Frame rate

  The original Game Boy draws about 59.7 frames every second. That number comes from the LCD, not from a setting in the game. There is no 30 fps mode and no 120 fps mode.

• Video RAM

  Video RAM is 8 kilobytes inside the Game Boy, from address 8000 to 9FFF. It holds the tile pictures and the two background maps. It does not hold your ROM, and it does not hold a save.