some kind of board game like reversi/othello but with colors?

board.go

package main

import "fmt"

func main() {

	initialBoard := [][]int{
		[]int{1, 1, 1, 4},
		[]int{1, 1, 2, 4},
		[]int{2, 1, 2, 4},
		[]int{1, 1, 2, 4},
	}

	// will print [[3 3 3 4] [3 3 2 4] [2 3 2 4] [1 3 2 4]]
	fmt.Printf("%v ", nextTurn(3, initialBoard))
}

func nextTurn(c int, board [][]int) [][]int {
	oldc := board[0][0]
	board[0][0] = c
	return nextTurnR(c, oldc, 0, 0, board)
}

func nextTurnR(c, oldc, x, y int, board [][]int) [][]int {
	if y+1 < len(board[x]) {
		if board[x][y+1] == oldc {
			board[x][y+1] = c
			board = nextTurnR(c, oldc, x, y+1, board)
		}
	}
	if x+1 < len(board) {
		if board[x+1][y] == oldc {
			board[x+1][y] = c
			board = nextTurnR(c, oldc, x+1, y, board)
		}
	}
	return board
}