fill function (paint style)

function fill(sq, end_condition) {
    var matrix = {}
    var queue = [sq]
    while(queue.length > 0) {
      var sq = queue.shift()
      var ns = neighbours(sq, matrix)
      if(end_condition ( ns ) {
        return true
      }
      queue = queue.concat(ns)
      matrix[key.join(",")] = 1
    }
  
    return false
  }
    
function neighbours(sq, matrix) {
    //get neighbours
    var ret = []
    var sqs = [[sq[0]+1,sq[1]], [sq[0]-1,sq[1]], [sq[0],sq[1]+1], [sq[0],sq[1]-1]]
    for(var i in sqs) {
      var s = sqs[i]
      if( no_wall || on board && !matrix[s.join(",")])
        ret.push(sq)
    }
  }