Engine limits

What a game can hold: colours, models, rooms and ROM size. The editor, or the build, checks every limit below and refuses to build a game that goes over.

Screen and colour

What	Limit	Why it matters
3D window	128 by 96 pixels	Live 3D, as in the cube and the room, fills this window.
Screen	160 by 144 pixels	Fixed-camera rooms and menus use the whole screen.
Colours per tile	4	Each 8 by 8 tile picks one palette of four colours.
Palettes per room view	8	A baked view needs no more than 8 palettes in all.
Unique tiles per room view	512	Repeating tiles are free; new ones count.
Palettes per screen image	6	Two more are kept for the interface.

Models

What	Limit	Why it matters
Vertices per character part	32	Keep shapes simple; flat shading makes low detail look intentional.
Faces per character part	32	Faces have 3 or 4 corners.
Vertex position	whole numbers within 85 of the part centre	Larger shapes are built from several parts.
Door look	32 vertices and 32 faces per piece	Door animations follow the same model rules.
Door width and height	16 to 64, and 32 to 112	A door look has to fit the wall it sits in.

Characters

What	Limit	Why it matters
Character size on screen	fits a 48 by 48 pixel box	A character taller or wider than that on screen is refused.
Enemies per view	1	A view shows at most one enemy.
Colour palettes per character	1	All of a character's parts share one palette of three colours.
Characters in a game	7	Placed characters and character-select entries together.
Sprites on one line	10	The player and the view's enemy must fit within the hardware's limit.
Animation	1 to 255 frames, 1 to 255 fps	Each character needs its basic animations.

World

What	Limit	Why it matters
Room walkable area	255 cells per side	A cell is 8 units, so a room is about 2000 units across.
Rooms	no fixed count	Limited by the 255 camera views and by ROM space.
Camera views	255	Every walkable cell must be covered by a camera.
Distance from a camera	about 1960 units	Cells farther from every camera of their room are refused.
Occluders per view	8	Foreground pieces the player can walk behind.
Screens	254	Title, menu and select screens all count.
Inventory screens	1	START opens the one inventory.

Items

What	Limit	Why it matters
Items	32	Each has a 16 by 16 icon with 3 colours and transparent.
Item name	12 characters	The name is drawn with the game font.
Stack limit	1 to 99	How many of an item the player can hold.
Pickups	64 in the game, 4 in a room	Keep rooms uncluttered.
Characters when items exist	6	Items use one of the 7 sprite palettes.

ROM size

What	Limit	Why it matters
The cube and the room	64 KB	The two 3D examples.
Dead Pixels	256 KB	A game made in the editor is 256 KB: its Game Boy pictures and its sound have banks of their own.
Largest ROM	4 MB	The largest ROM the engine builds.

Pictures and animation frames are what fill a ROM. The space line at the bottom of the editor shows how full yours is.

On a Game Boy

A game made in the editor also plays on a Game Boy, Game Boy Pocket or Super Game Boy, in four greys. The editor makes the grey version of every room view and screen for you, and its DMG switch previews it.

What	Limit	Why it matters
Shades	4 greys	The editor maps each picture's colours to the four shades.
Unique tiles per room view	204	The Game Boy has one bank of tile memory; the editor merges the most alike tiles to fit.
Unique tiles per screen image	126	The rest is kept for the font and the interface.
If it does not fit	Color only	A game whose Game Boy pictures do not fit is built for the Game Boy Color alone, and the editor warns you.

Speed

The 3D examples run at roughly 12 to 20 frames per second on a Game Boy Color, and at about half that on a Game Boy, which has half the clock speed. Doors animate at about 10. A smaller shape count and fewer faces per view keep a room quick.