Cellular Automata Sierpinski's Triangle https://go.dev/play/p/JZ5JVjIfMcD

sierpinski.go

package main

import (
	"fmt"
	"strings"
)

func cell(cells []byte, rule int) {
	t := [8]byte{}
	for i := 0; i < 8; i++ {
		switch rule & 1 {
		case 0:
			t[i] = ' '
		case 1:
			t[i] = 'X'
		}
		rule >>= 1
	}
	for row := 0; row < 100; row++ {
		fmt.Println(string(cells))
		state := 0
		if cells[0] == 'X' {
			state = 1
		}
		for i := 1; i < len(cells); i++ {
			state = (state << 1) & 7
			if cells[i] == 'X' {
				state = state | 1
			}
			cells[i-1] = t[state]
		}
		state = (state << 1) & 7
		cells[len(cells)-1] = t[state]
	}
}

func main() {
	buf := []byte(strings.Repeat(" ", 120))

	// single X in the middle
	buf[len(buf)/2] = 'X'
	cell(buf, 18) // 18 = 00010010 binary
}