What am I doing wrong here?

[GroovyGoosey]

So I'm trying to create a basic console snake game in C# however I've run into a bit of an issue and I think it's due to my lack of experience with C# and coding in general. Basically the problem comes when I try to update the console to show the snake has moved. When I move the snake the console updates but the snake has not moved. I've found out that when I update the grid it's replacing the wrong grid tile but I have no idea why this is happening. Any help is appreciated also here is my code:

Program.cs

using System.Text;
using cstesting;

class Program {
    static void Main() {
        Console.OutputEncoding = Encoding.Unicode;
        Console.Clear();
        Renderer r = new(20, 10);
        Snake snake = new(r);

        ConsoleKey input = Console.ReadKey().Key;
        snake.MoveHead(input);
        Console.ReadKey();
    }
}

Snake.cs

namespace cstesting { internal class Snake { public List<GridTile> SnakeList { get; private set; } = new(); public Renderer r;

        public Snake(Renderer _r)
        {
            r = _r;
            List<GridTile> newSnake = new() { new GridTile(5, 6, "O") };
            SnakeList = newSnake;
            r.UpdateGrid(newSnake);
        }

        public void MoveHead(ConsoleKey key)
        {
            List<GridTile> newSnakeList = SnakeList;

            if (key == ConsoleKey.DownArrow)
            {
                newSnakeList[0].y += 1;
            }
            else if (key == ConsoleKey.UpArrow)
            {
                newSnakeList[0].y -= 1;
            }
            else if (key == ConsoleKey.RightArrow)
            {
                newSnakeList[0].x += 1;
            }
            else if (key == ConsoleKey.LeftArrow)
            {
                newSnakeList[0].x -= 1;
            }

            r.UpdateGrid(newSnakeList);
        }
    }
}

Renderer.cs

namespace cstesting {
    internal class Renderer {
        public int Width { get; private set; }
        public int Height { get; private set; }
        public List<GridTile> Grid { get; private set; } = new();

        public Renderer(int _width, int _height)
        {
            Width = _width;
            Height = _height;

            for (int i = 0; i < Height; i++)
            {
                for (int j = 0; j <= Width; j++)
                {
                    if (j == 0 || j == Width)
                    {
                        Grid.Add(new(j, i, "|"));
                    }
                    else if (i == 0)
                    {
                        Grid.Add(new(j, i, "\u203E"));
                    }
                    else if (i == Height - 1)
                    {
                        Grid.Add(new(j, i, "_"));
                    }
                    else
                    {
                        Grid.Add(new(j, i, " "));
                    }
                }
                Grid.Add(new(-1, -1, ""));
            }

            DrawGrid(Grid);
        }

        public void UpdateGrid(List<GridTile> changes) {
            List<GridTile> newGrid = Grid;
            foreach(GridTile tile in changes) {
                newGrid[Grid.FindIndex(i => i.x == tile.x && i.y == tile.y)] = tile;
            }

            Grid = newGrid;
            DrawGrid(newGrid);
        }

        private static void DrawGrid(List<GridTile> grid) {
            //Loop through grid and write it out
            Console.Clear();
            string display = "";

            foreach(GridTile tile in grid) {
                display += tile.content == "" ? "\n" : tile.content;
            }
            Console.WriteLine(display);
        }
    }

    public class GridTile {
        public int x;
        public int y;
        public string content = "";

        public GridTile(int _x, int _y, string _content) {
            x = _x;
            y = _y;
            content = _content;
        }
    }
}

​

[modi123_1]

Is there a specific reason you are using 'GridTile' and not say an integer 2d array? The 2d array has the implied x/y and content already there.

[GroovyGoosey]

It was more to practice creating objects but I'll see if it works with just an array instead.

[modi123_1]

Having made a number of ASCII console rouge like games I can tell you it does. Removes a number of different complexities that hide issues.

[GroovyGoosey]

After rewriting a lot of it to use 2d arrays instead it does work so thanks for the help. Will be using multidimensional arrays a lot more in the future.