Conway's Game of Life

An implementation of Conway's Game of Life in Lua for the TIC-80 fantasy console.

Rules, from Wikipedia:

Any live cell with two or three live neighbours survives.
Any dead cell with three live neighbours becomes a live cell.
All other live cells die in the next generation. Similarly, all other dead cells stay dead.

Code

You can download the .tic file and load it up in TIC-80 to view the code/edit the game.

-- title:  Conway's Game of Life
-- author: Aleksandr Hovhannisyan
-- desc:   Implementation of Conway's Game of Life in Lua
-- script: lua

function BOOT()
	-- The TIC() function runs at 60 FPS
	FPS_TIC=60
	-- Change this to run the game slower
	FPS_DESIRED=60
    -- Screen dimensions (engine constants)
	Screen={
		WIDTH	=240,
		HEIGHT  =136,
	}
	-- Color palette
	Color={
		BLACK=0,
		WHITE=12,
	}
	-- Frame/generation counter, increments at TIC_FPS
	generation=0
	-- Likelihood of a cell spawning alive in gen 0
	ALIVE_SPAWN_CHANCE=0.1
	-- Possible cell states
	CellState={
		DEAD	=false,
		ALIVE	=true,
	}
	-- Map cell states to colors
	CellColor={
		[CellState.ALIVE]   =Color.BLACK,
		[CellState.DEAD]    =Color.WHITE,
	}
	-- Game rules
	Threshold={
		OVERPOPULATION=3,
		UNDERPOPULATION=2,
		REPRODUCTION=3,
	}
	-- Track cell state for every pixel
	-- in a 1D array (which we'll interpret
	-- as a 2D screen when drawing).
	oldCells={}
	for index=0,Screen.WIDTH*Screen.HEIGHT do
		local diceRoll=math.random()
		local state=CellState.DEAD
		if diceRoll<=ALIVE_SPAWN_CHANCE then
			state=CellState.ALIVE
		end
		oldCells[index]=state
	end
	-- Track old and new generation in
	-- separate tables upfront to avoid
	-- creating a new table each frame
	newCells={}
	CopyTable(oldCells,newCells)
end

-- Only works if values are primitive,
-- but they are in our case. If each cell
-- was itself a table, we'd need to modify this
function CopyTable(source,target)
	for k,v in pairs(source) do
		target[k]=v
	end
end

-- Returns the number of alive neighbor cells for the cell at the given index
function GetNumAliveNeighbors(cells,index)
	local numAliveNeighbors=0
	-- row 0:  		 0			1 		2 		3 ... 238 239
	-- row 1: 		240 241 242 243 ... 478 479
	local neighbors={
		-- No need to check that these indices are in bounds since
		-- tables in Lua can have any index, so if the index is out of
		-- bounds, then the value we'll look at will just be nil
		left		=index-1,
		right		=index+1,
		top			=index-Screen.WIDTH,
		topLeft		=index-Screen.WIDTH-1,
		topRight	=index-Screen.WIDTH+1,
		bottom		=index+Screen.WIDTH,
		bottomLeft	=index+Screen.WIDTH-1,
		bottomRight	=index+Screen.WIDTH+1,
	}
	for direction,neighborIndex in pairs(neighbors) do
		if cells[neighborIndex]==CellState.ALIVE then
			numAliveNeighbors=numAliveNeighbors+1
		end
	end
	return numAliveNeighbors
end

-- Game update loop. Implements game rules
-- and draws cells on the display.
function Update()
	for index,state in pairs(oldCells) do
		local numAliveNeighbors=GetNumAliveNeighbors(oldCells,index)
		local newState=state
		-- Currently alive
		if state==CellState.ALIVE then
			if numAliveNeighbors<Threshold.UNDERPOPULATION or 
               numAliveNeighbors>Threshold.OVERPOPULATION
			then
				newState=CellState.DEAD
			end
		-- Currently dead
		else
			if numAliveNeighbors==Threshold.REPRODUCTION then
				newState=CellState.ALIVE
			end
		end
		newCells[index]=newState
		DrawCell(index,newState)
	end
	-- This "new" generation will be the next
	-- generation's old generation, so copy it now
	CopyTable(newCells,oldCells)
end

function DrawCell(index,state)
	poke(0x00000+index,CellColor[state],4)
end

function TIC()
	if generation%(FPS_TIC/FPS_DESIRED)==0 then
		Update()
	end
	generation=generation+1
end

AleksandrHovhannisyan/conways-game-of-life

Conway's Game of Life

Code