AdventOfCode 2018 Day 09

void Main()
{
    ///TEST CODE
    if(PlayGame(09, 0025) != 000032) throw new Exception("Failed Game");
    if(PlayGame(10, 1618) != 008317) throw new Exception("Failed Game");
    if(PlayGame(13, 7999) != 146373) throw new Exception("Failed Game");
    if(PlayGame(17, 1104) != 002764) throw new Exception("Failed Game");
    if(PlayGame(21, 6111) != 054718) throw new Exception("Failed Game");
    if(PlayGame(30, 5807) != 037305) throw new Exception("Failed Game");

    //GET DATA
    var aoc = new AdventOfCode(2018, 9);

    //PARSE IT
    var i = Parse(aoc.InputLines[0]);

    //Submit
    aoc.SubmitAnswer(PlayGame(i.playerCount, i.lastMarble), Part.A);
    aoc.SubmitAnswer(PlayGame(i.playerCount, i.lastMarble * 100), Part.B);
}

//Parse
(int playerCount, int lastMarble) Parse(string line)
{
    var splt = line.Split(' ');
    return(int.Parse(splt[0]), int.Parse(splt[6]));
}


long PlayGame(int playerCount, int lastMarble)
{
    //the players and their score
    var players = new long[playerCount];
    int playerPosition = 0;

    //circle with the marbles, small extension added to circular usage
    var circle = new LinkedList<int>();

    //the currentMarble
    int currentMarble = 0;

    //add the first
    circle.AddFirst(currentMarble++);

    //the position we are working from
    var position = circle.First;

    //loop till last marble
    while (currentMarble <= lastMarble)
    {
        //move the playerposition by 1
        playerPosition++;

        //special moment?
        if (currentMarble % 23 == 0)
        {
            //add the score
            players[playerPosition % playerCount] += currentMarble++;

            //move 7 times (bit ugly but save a for loop SPPEEED!
            position = position.GetPrevious().GetPrevious().GetPrevious().GetPrevious().GetPrevious().GetPrevious().GetPrevious();

            //add the new current marble to the score
            players[playerPosition % playerCount] += position.Value;

            //this needs to be removed
            var toRemove = position;

            //get the new position
            position = position.GetNext();

            //and remove
            circle.Remove(toRemove);
        }
        else
        {
            //move
            position = position.GetNext();

            //add marble
            position = circle.AddAfter(position, currentMarble++);
        }
    }

    //return score
    return players.Max();
}

//extension, for easy circular list usage.
public static class test
{
    public static LinkedListNode<int> GetNext(this LinkedListNode<int> item)
    {
        if(item.List.Last == item) return item.List.First;
        else return item.Next;
    }

    public static LinkedListNode<int> GetPrevious(this LinkedListNode<int> item)
    {
        if (item.List.First == item) return item.List.Last;
        else return item.Previous;
    }
}

// Define other methods and classes here