// Conway's Game of Life on Gno — the entire board lives on-chain.
// Anyone can call Step() to tick the simulation forward, load classic
// patterns, or sculpt cells one by one.
package life
import (
"strconv"
"strings"
)
const (
MaxWidth = 50
MaxHeight = 40
)
var (
width = 20
height = 15
cells []bool
generation int
population int
)
func init() {
initBoard(width, height)
LoadPreset("glider")
}
func initBoard(w, h int) {
if w < 1 {
w = 1
}
if w > MaxWidth {
w = MaxWidth
}
if h < 1 {
h = 1
}
if h > MaxHeight {
h = MaxHeight
}
width = w
height = h
cells = make([]bool, width*height)
generation = 0
population = 0
}
func cellIdx(x, y int) int {
return y*width + x
}
func alive(x, y int) bool {
if x < 0 || x >= width || y < 0 || y >= height {
return false
}
return cells[cellIdx(x, y)]
}
func countNeighbors(x, y int) int {
n := 0
for dy := -1; dy <= 1; dy++ {
for dx := -1; dx <= 1; dx++ {
if dx == 0 && dy == 0 {
continue
}
if alive(x+dx, y+dy) {
n++
}
}
}
return n
}
// Step advances the simulation by exactly one generation.
func Step() {
next := make([]bool, width*height)
newPop := 0
for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
n := countNeighbors(x, y)
var live bool
if alive(x, y) {
live = n == 2 || n == 3
} else {
live = n == 3
}
next[cellIdx(x, y)] = live
if live {
newPop++
}
}
}
cells = next
population = newPop
generation++
}
// MultiStep advances the simulation by n generations (capped at 100).
func MultiStep(n int) {
if n < 1 {
n = 1
}
if n > 100 {
n = 100
}
for i := 0; i < n; i++ {
Step()
}
}
// SetCell sets or clears a specific cell.
func SetCell(x, y int, live bool) {
if x < 0 || x >= width || y < 0 || y >= height {
return
}
i := cellIdx(x, y)
was := cells[i]
cells[i] = live
if live && !was {
population++
} else if !live && was {
population--
}
}
// Reset clears the board and resizes it to w×h.
func Reset(w, h int) {
initBoard(w, h)
}
// LoadPreset loads a classic Game of Life pattern onto the current board.
// Names: glider, blinker, toad, beacon, block, pulsar.
func LoadPreset(name string) {
for i := range cells {
cells[i] = false
}
generation = 0
population = 0
cx := width / 2
cy := height / 2
switch name {
case "glider":
// .O.
// ..O
// OOO
SetCell(1, 0, true)
SetCell(2, 1, true)
SetCell(0, 2, true)
SetCell(1, 2, true)
SetCell(2, 2, true)
case "blinker":
// OOO (period-2 oscillator)
SetCell(cx-1, cy, true)
SetCell(cx, cy, true)
SetCell(cx+1, cy, true)
case "toad":
// period-2 oscillator
SetCell(cx, cy-1, true)
SetCell(cx+1, cy-1, true)
SetCell(cx+2, cy-1, true)
SetCell(cx-1, cy, true)
SetCell(cx, cy, true)
SetCell(cx+1, cy, true)
case "beacon":
// period-2 oscillator
SetCell(cx-2, cy-2, true)
SetCell(cx-1, cy-2, true)
SetCell(cx-2, cy-1, true)
SetCell(cx, cy, true)
SetCell(cx+1, cy, true)
SetCell(cx, cy+1, true)
SetCell(cx+1, cy+1, true)
case "block":
// 2×2 still life
SetCell(cx, cy, true)
SetCell(cx+1, cy, true)
SetCell(cx, cy+1, true)
SetCell(cx+1, cy+1, true)
case "pulsar":
// period-3 oscillator (needs at least 17×17 board)
for _, d := range []int{-4, -3, -2, 2, 3, 4} {
SetCell(cx+d, cy-6, true)
SetCell(cx+d, cy-1, true)
SetCell(cx+d, cy+1, true)
SetCell(cx+d, cy+6, true)
SetCell(cx-6, cy+d, true)
SetCell(cx-1, cy+d, true)
SetCell(cx+1, cy+d, true)
SetCell(cx+6, cy+d, true)
}
default:
LoadPreset("glider")
}
}
// Render returns a Markdown snapshot of the current board.
func Render(path string) string {
out := "# Conway's Game of Life\n\n"
out += "> A classic cellular automaton, ported to Gno — board state lives on-chain.\n\n"
out += "**Generation:** " + strconv.Itoa(generation)
out += " | **Population:** " + strconv.Itoa(population)
out += " | **Board:** " + strconv.Itoa(width) + "×" + strconv.Itoa(height) + "\n\n"
border := "+" + strings.Repeat("-", width) + "+\n"
out += "```\n"
out += border
for y := 0; y < height; y++ {
row := "|"
for x := 0; x < width; x++ {
if alive(x, y) {
row += "O"
} else {
row += "."
}
}
row += "|\n"
out += row
}
out += border
out += "```\n\n"
out += "## Transactions\n\n"
out += "| Call | Effect |\n"
out += "|---|---|\n"
out += "| `Step()` | Advance one generation |\n"
out += "| `MultiStep(n)` | Advance *n* generations (max 100) |\n"
out += "| `SetCell(x, y, alive)` | Flip a single cell |\n"
out += "| `Reset(w, h)` | Clear and resize (max " + strconv.Itoa(MaxWidth) + "×" + strconv.Itoa(MaxHeight) + ") |\n"
out += "| `LoadPreset(name)` | `glider` · `blinker` · `toad` · `beacon` · `block` · `pulsar` |\n\n"
out += "## Rules\n\n"
out += "1. A live cell with 2 or 3 live neighbours survives.\n"
out += "2. A dead cell with exactly 3 live neighbours becomes alive.\n"
out += "3. All other cells die or remain dead.\n"
return out
}