ebiten/examples/life/main.go

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// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2015 Martin Lindhe
// SPDX-FileCopyrightText: 2016 The Ebitengine Authors
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package main
import (
"log"
"math/rand"
"time"
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"github.com/hajimehoshi/ebiten/v2"
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)
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func init() {
rand.Seed(time.Now().UnixNano())
}
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// World represents the game state.
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type World struct {
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area []bool
width int
height int
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}
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// NewWorld creates a new world.
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func NewWorld(width, height int, maxInitLiveCells int) *World {
w := &World{
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area: make([]bool, width*height),
width: width,
height: height,
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}
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w.init(maxInitLiveCells)
return w
}
// init inits world with a random state.
func (w *World) init(maxLiveCells int) {
for i := 0; i < maxLiveCells; i++ {
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x := rand.Intn(w.width)
y := rand.Intn(w.height)
w.area[y*w.width+x] = true
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}
}
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// Update game state by one tick.
func (w *World) Update() {
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width := w.width
height := w.height
next := make([]bool, width*height)
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for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
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pop := neighbourCount(w.area, width, height, x, y)
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switch {
case pop < 2:
// rule 1. Any live cell with fewer than two live neighbours
// dies, as if caused by under-population.
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next[y*width+x] = false
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case (pop == 2 || pop == 3) && w.area[y*width+x]:
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// rule 2. Any live cell with two or three live neighbours
// lives on to the next generation.
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next[y*width+x] = true
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case pop > 3:
// rule 3. Any live cell with more than three live neighbours
// dies, as if by over-population.
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next[y*width+x] = false
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case pop == 3:
// rule 4. Any dead cell with exactly three live neighbours
// becomes a live cell, as if by reproduction.
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next[y*width+x] = true
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}
}
}
w.area = next
}
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// Draw paints current game state.
func (w *World) Draw(pix []byte) {
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for i, v := range w.area {
if v {
pix[4*i] = 0xff
pix[4*i+1] = 0xff
pix[4*i+2] = 0xff
pix[4*i+3] = 0xff
} else {
pix[4*i] = 0
pix[4*i+1] = 0
pix[4*i+2] = 0
pix[4*i+3] = 0
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}
}
}
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func max(a, b int) int {
if a < b {
return b
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}
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return a
}
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func min(a, b int) int {
if a < b {
return a
}
return b
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}
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// neighbourCount calculates the Moore neighborhood of (x, y).
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func neighbourCount(a []bool, width, height, x, y int) int {
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c := 0
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for j := -1; j <= 1; j++ {
for i := -1; i <= 1; i++ {
if i == 0 && j == 0 {
continue
}
x2 := x + i
y2 := y + j
if x2 < 0 || y2 < 0 || width <= x2 || height <= y2 {
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continue
}
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if a[y2*width+x2] {
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c++
}
}
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}
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return c
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}
const (
screenWidth = 320
screenHeight = 240
)
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type Game struct {
world *World
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pixels []byte
}
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func (g *Game) Update() error {
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g.world.Update()
return nil
}
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func (g *Game) Draw(screen *ebiten.Image) {
if g.pixels == nil {
g.pixels = make([]byte, screenWidth*screenHeight*4)
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}
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g.world.Draw(g.pixels)
screen.WritePixels(g.pixels)
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}
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func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
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}
func main() {
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g := &Game{
world: NewWorld(screenWidth, screenHeight, int((screenWidth*screenHeight)/10)),
}
ebiten.SetWindowSize(screenWidth*2, screenHeight*2)
ebiten.SetWindowTitle("Game of Life (Ebitengine Demo)")
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if err := ebiten.RunGame(g); err != nil {
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log.Fatal(err)
}
}