\begin{Verbatim}[commandchars=\\\{\}]
// by gera
// public domain
package hello\PYZus{}life

import \PYZdq{}core:slice\PYZdq{}
import sdl \PYZdq{}vendor:sdl3\PYZdq{}


ClearBoard :: proc(pixels : [][4]u8, color : [4]u8) \PYZob{}
	for i in 0..\PYZlt{}len(pixels) \PYZob{}
		pixels[i] = color
	\PYZcb{}
\PYZcb{}

DrawCells :: proc(cells : \PYZca{}map[[2]i32]bool, pixels : [][4]u8, color : [4]u8, w, h : i32) \PYZob{}
	for cell in cells \PYZob{}
		if cell.x \PYZgt{}= 0 \PYZam{}\PYZam{} cell.y \PYZgt{}= 0 \PYZam{}\PYZam{} cell.x \PYZlt{} w \PYZam{}\PYZam{} cell.y \PYZlt{} h \PYZob{}
			pixels[cell.x + cell.y * w] = color
		\PYZcb{}
	\PYZcb{}
\PYZcb{}

CountNeighbors :: proc(cells : \PYZca{}map[[2]i32]bool, pos : [2]i32) \PYZhy{}\PYZgt{} i32
\PYZob{}
	count : i32
	count += i32(cells[\PYZob{}pos.x + 1, pos.y\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x + 1, pos.y + 1\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x, pos.y + 1\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x \PYZhy{} 1, pos.y + 1\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x \PYZhy{} 1, pos.y\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x \PYZhy{} 1, pos.y \PYZhy{} 1\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x, pos.y \PYZhy{} 1\PYZcb{}])
	count += i32(cells[\PYZob{}pos.x + 1, pos.y \PYZhy{} 1\PYZcb{}])
	return count
\PYZcb{}

ApplyRulesOnCell :: proc(cellscur, cellsnext : \PYZca{}map[[2]i32]bool, pos : [2]i32)
\PYZob{}
	neighbors := CountNeighbors(cellscur, pos)
	alive := cellscur[pos]
	if (alive \PYZam{}\PYZam{} (neighbors \PYZlt{} 2 || neighbors \PYZgt{} 3)) do delete\PYZus{}key(cellsnext, pos)
	else if (!alive \PYZam{}\PYZam{} neighbors == 3) do cellsnext[pos] = true
	else if (alive \PYZam{}\PYZam{} (neighbors == 2 || neighbors == 3)) do cellsnext[pos] = true
\PYZcb{}

ComputeLife :: proc(cellscur, cellsnext : \PYZca{}map[[2]i32]bool)
\PYZob{}
	clear(cellsnext)
	for cell in cellscur \PYZob{}
		x := cell[0]
		y := cell[1]
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x, y\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x + 1, y\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x + 1, y + 1\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x, y + 1\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x \PYZhy{} 1, y + 1\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x \PYZhy{} 1, y\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x \PYZhy{} 1, y \PYZhy{} 1\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x, y \PYZhy{} 1\PYZcb{})
		ApplyRulesOnCell(cellscur, cellsnext, \PYZob{}x + 1, y \PYZhy{} 1\PYZcb{})
	\PYZcb{}
\PYZcb{}

main :: proc() \PYZob{}
	result := sdl.Init(\PYZob{}.VIDEO\PYZcb{})
	window : \PYZca{}sdl.Window
	renderer : \PYZca{}sdl.Renderer
	result = sdl.CreateWindowAndRenderer(\PYZdq{}Game of Life\PYZdq{}, width = 640, height = 480,
										 window\PYZus{}flags = \PYZob{}.RESIZABLE,\PYZcb{},
										 window = \PYZam{}window, renderer = \PYZam{}renderer)
	texture := sdl.CreateTexture(renderer, sdl.PixelFormat.ABGR8888, sdl.TextureAccess.STREAMING, 320, 240)
	sdl.SetRenderLogicalPresentation(renderer, texture.w, texture.h, sdl.RendererLogicalPresentation.LETTERBOX)
	sdl.SetTextureScaleMode(texture, sdl.ScaleMode.NEAREST)

	cells1 : map[[2]i32]bool
	cells2 : map[[2]i32]bool
	cellsfront := \PYZam{}cells1
	cellsback := \PYZam{}cells2

/* initial state:
	****
	 *
	  *
	  *
*/
	cellsfront[\PYZob{}0+texture.w/2, 0+texture.h/2\PYZcb{}] = true
	cellsfront[\PYZob{}1+texture.w/2, 0+texture.h/2\PYZcb{}] = true
	cellsfront[\PYZob{}2+texture.w/2, 0+texture.h/2\PYZcb{}] = true
	cellsfront[\PYZob{}3+texture.w/2, 0+texture.h/2\PYZcb{}] = true
	cellsfront[\PYZob{}1+texture.w/2, 1+texture.h/2\PYZcb{}] = true
	cellsfront[\PYZob{}2+texture.w/2, 2+texture.h/2\PYZcb{}] = true
	cellsfront[\PYZob{}2+texture.w/2, 3+texture.h/2\PYZcb{}] = true

	running : bool = true
	time\PYZus{}start : u64
	loop: for running \PYZob{}
		time\PYZus{}start = sdl.GetTicksNS()
		event : sdl.Event
		result = sdl.PollEvent(\PYZam{}event)
		\PYZsh{}partial switch event.type \PYZob{}
			case .QUIT:
			running = false
			break loop
		\PYZcb{}

		pixels\PYZus{}rawptr : rawptr
		pitch : i32
		sdl.LockTexture(texture, nil, \PYZam{}pixels\PYZus{}rawptr, \PYZam{}pitch)
		pixels := slice.from\PYZus{}ptr(([\PYZca{}][4]u8)(pixels\PYZus{}rawptr), int(texture.w) * int(texture.h))
		ClearBoard(pixels, \PYZob{}200, 200, 200, 255\PYZcb{})
		DrawCells(cellsfront, pixels, \PYZob{}0, 0, 255, 255\PYZcb{}, texture.w, texture.h)
		sdl.UnlockTexture(texture)
		sdl.RenderClear(renderer)
		sdl.RenderTexture(renderer, texture, nil, nil)
		sdl.RenderPresent(renderer)

		ComputeLife(cellsfront, cellsback)
		cellsfront, cellsback = cellsback, cellsfront

		time\PYZus{}end := sdl.GetTicksNS()
		// do more generations but maintain the target fps
		for time\PYZus{}end \PYZhy{} time\PYZus{}start \PYZlt{} 1e9/30 \PYZob{}
			ComputeLife(cellsfront, cellsback)
			cellsfront, cellsback = cellsback, cellsfront
			// also handle events so the window doesn\PYZsq{}t lag
			result = sdl.PollEvent(\PYZam{}event)
			\PYZsh{}partial switch event.type \PYZob{}
				case .QUIT:
				running = false
				break loop
			\PYZcb{}
			time\PYZus{}end = sdl.GetTicksNS()
		\PYZcb{}
	\PYZcb{}

	sdl.DestroyRenderer(renderer)
	sdl.DestroyWindow(window)
	sdl.Quit()
\PYZcb{}
\end{Verbatim}