Program.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using System.Threading;

bool closeRequested = false;
State state = State.Main;
Stopwatch stopwatch = new();
TimeSpan framerate = TimeSpan.FromSeconds(1d / 60d);
bool direction = default;
bool playerGoesFirst = default;
int x = 0;
int y = 0;
int x_max = 38;
int y_max = 14;
List<((int X, int Y)? Position, bool Player)> darts = new();
int computer_x = default;
int computer_y = default;
int computer_skip = default;

try
{
	Console.CursorVisible = false;
	Console.OutputEncoding = Encoding.UTF8;
	while (!closeRequested)
	{
		Render();
		Update();
	}
}
finally
{
	Console.CursorVisible = true;
	Console.Clear();
	Console.WriteLine("Darts was closed.");
}

void Update()
{
	switch (state)
	{
		case State.Main:
			PressEnterToContinue();
			if (closeRequested)
			{
				return;
			}
			playerGoesFirst = Random.Shared.Next(0, 2) % 2 is 0;
			state = State.ConfirmRandomTurnOrder;
			Console.Clear();
			break;

		case State.ConfirmRandomTurnOrder:
			PressEnterToContinue();
			if (closeRequested)
			{
				return;
			}
			state = playerGoesFirst
				? State.PlayerHorizontal
				: State.ComputerHorizontal;
			direction = true;
			x = 0;
			if (!playerGoesFirst)
			{
				computer_x = Random.Shared.Next(x_max + 1);
				computer_skip = Random.Shared.Next(1, 4);
			}
			stopwatch.Restart();
			Console.Clear();
			break;

		case State.ConfirmPlayerThrow:
			PressEnterToContinue();
			if (closeRequested)
			{
				return;
			}
			if (darts.Count >= 10)
			{
				state = State.ConfirmGameEnd;
				Console.Clear();
				break;
			}
			state = State.ComputerHorizontal;
			direction = true;
			x = 0;
			computer_x = Random.Shared.Next(x_max + 1);
			computer_skip = Random.Shared.Next(1, 4);
			stopwatch.Restart();
			Console.Clear();
			break;

		case State.ConfirmComputerThrow:
			PressEnterToContinue();
			if (closeRequested)
			{
				return;
			}
			if (darts.Count >= 10)
			{
				state = State.ConfirmGameEnd;
				Console.Clear();
				break;
			}
			state = State.PlayerHorizontal;
			direction = true;
			x = 0;
			stopwatch.Restart();
			Console.Clear();
			break;

		case State.PlayerHorizontal or State.ComputerHorizontal:
			if (KeyPressed() && state is State.PlayerHorizontal)
			{
				if (closeRequested)
				{
					return;
				}
				state = State.PlayerVertical;
				direction = true;
				y = 0;
				stopwatch.Restart();
				Console.Clear();
				break;
			}
			if (closeRequested)
			{
				return;
			}
			if (direction)
			{
				x++;
			}
			else
			{
				x--;
			}
			if (state is State.ComputerHorizontal && x == computer_x)
			{
				computer_skip--;
				if (computer_skip < 0)
				{
					state = State.ComputerVertical;
					direction = true;
					y = 0;
					stopwatch.Restart();
					computer_y = Random.Shared.Next(y_max + 1);
					computer_skip = Random.Shared.Next(1, 4);
				}
			}
			if (x <= 0 || x >= x_max)
			{
				if (x < 0) x = 0;
				if (x > x_max) x = x_max;
				direction = !direction;
			}
			ControlFrameRate();
			break;

		case State.PlayerVertical or State.ComputerVertical:
			if (KeyPressed() && state is State.PlayerVertical)
			{
				if (closeRequested)
				{
					return;
				}
				state = State.ConfirmPlayerThrow;
				(int X, int Y)? position = (x, y);
				for (int i = 0; i < darts.Count; i++)
				{
					if (darts[i].Position == (x, y))
					{
						darts[i] = (null, darts[i].Player);
						position = null;
					}
				}
				darts.Add(new(position, true));
				Console.Clear();
				break;
			}
			if (closeRequested)
			{
				return;
			}
			if (direction)
			{
				y++;
			}
			else
			{
				y--;
			}
			if (state is State.ComputerVertical && y == computer_y)
			{
				computer_skip--;
				if (computer_skip < 0)
				{
					state = State.ConfirmComputerThrow;
					(int X, int Y)? position = (x, y);
					for (int i = 0; i < darts.Count; i++)
					{
						if (darts[i].Position == (x, y))
						{
							darts[i] = (null, darts[i].Player);
							position = null;
						}
					}
					darts.Add(new(position, false));
					Console.Clear();
					break;
				}
			}
			if (y <= 0 || y >= y_max)
			{
				if (y < 0) y = 0;
				if (y > y_max) y = y_max;
				direction = !direction;
			}
			ControlFrameRate();
			break;

		case State.ConfirmGameEnd:
			PressEnterToContinue();
			if (closeRequested)
			{
				return;
			}
			state = State.Main;
			darts = new();
			break;

		default:
			throw new NotImplementedException();

	}
}

void ControlFrameRate()
{
	TimeSpan elapsed = stopwatch.Elapsed;
	if (framerate > elapsed)
	{
		Thread.Sleep(framerate - elapsed);
	}
	stopwatch.Restart();
}

void PressEnterToContinue()
{
	while (true)
	{
		switch (Console.ReadKey(true).Key)
		{
			case ConsoleKey.Enter: return;
			case ConsoleKey.Escape: closeRequested = true; return;
		}
	}
}

bool KeyPressed()
{
	bool keyPressed = false;
	while (Console.KeyAvailable)
	{
		keyPressed = true;
		if (Console.ReadKey(true).Key is ConsoleKey.Escape)
		{
			closeRequested = true;
		}
	}
	return keyPressed;
}

void Render()
{
	var render = new StringBuilder();

	if (state is State.Main)
	{
		StringBuilder output = new();
		output.AppendLine();
		output.AppendLine("  Darts");
		output.AppendLine();
		output.AppendLine("  Welcome to Darts. In this game you and the computer will");
		output.AppendLine("  throw darts at a dart board in attempts to get the most ");
		output.AppendLine("  points. If your dart lands on a line, it will round down");
		output.AppendLine("  amongst all the regions it is touching. If your dart lands");
		output.AppendLine("  on another dart it will knock both darts off the board so");
		output.AppendLine("  they will each be worth 0 points. You and the computer each");
		output.AppendLine("  get to throw 5 darts.");
		output.AppendLine();
		output.AppendLine("  Your darts: ○");
		output.AppendLine("  Computer's darts: ●");
		output.AppendLine();
		output.AppendLine("  Press [escape] at any time to close the game.");
		output.AppendLine();
		output.Append("  Press [enter] to begin...");
		Console.Clear();
		Console.Write(output);
		return;
	}

	string[] board =
	[
		"╔═══════╤═══════╤═══════╤═══════╤═══════╗",
		"║       │       │       │       │       ║",
		"║   1   │   2   │   3   │   2   │   1   ║",
		"║      ┌┴┐    ┌─┴─┐   ┌─┴─┐    ┌┴┐      ║",
		"╟──────┤6├────┤ 5 ├───┤ 5 ├────┤6├──────╢",
		"║      └┬┘    └─┬─┘   └─┬─┘    └┬┘      ║",
		"║   2   │   3   │   4   │   3   │   2   ║",
		"║       │       │  ┌─┐  │       │       ║",
		"╟───────┼───────┼──┤9├──┼───────┼───────╢",
		"║       │       │  └─┘  │       │       ║",
		"║   2   │   3   │   4   │   3   │   2   ║",
		"║      ┌┴┐    ┌─┴─┐   ┌─┴─┐    ┌┴┐      ║",
		"╟──────┤6├────┤ 5 ├───┤ 5 ├────┤6├──────╢",
		"║      └┬┘    └─┬─┘   └─┬─┘    └┬┘      ║",
		"║   1   │   2   │   3   │   2   │   1   ║",
		"║       │       │       │       │       ║",
		"╚═══════╧═══════╧═══════╧═══════╧═══════╝",
	];
	for (int i = 0; i < board.Length; i++)
	{
		for (int j = 0; j < board[i].Length; j++)
		{
			foreach (var dart in darts)
			{
				if (dart.Position == (j - 1, i - 1))
				{
					render.Append(dart.Player ? '○' : '●');
					goto DartRendered;
				}
			}
			render.Append(board[i][j]);
		DartRendered:
			continue;
		}
		if (state is State.PlayerHorizontal or State.PlayerVertical or State.ComputerHorizontal or State.ComputerVertical or State.ConfirmPlayerThrow or State.ConfirmComputerThrow)
		{
			render.Append(' ');
			if (i - 1 == y && state is not State.PlayerHorizontal and not State.ComputerHorizontal)
			{
				render.Append("│██│");
			}
			else
			{
				render.Append(i is 0 ? "┌──┐" : i == board.Length - 1 ? "└──┘" : "│  │");
			}
		}
		render.AppendLine();
	}
	if (state is State.PlayerHorizontal or State.PlayerVertical or State.ComputerHorizontal or State.ComputerVertical or State.ConfirmPlayerThrow or State.ConfirmComputerThrow)
	{
		render.AppendLine("┌───────────────────────────────────────┐");
		for (int j = 0; j <= x_max + 2; j++)
		{
			render.Append(
				j - 1 == x ? '█' :
				j is 0 ? '│' :
				j == x_max + 2 ? '│' :
				' ');
		}
		render.AppendLine();
		render.AppendLine("└───────────────────────────────────────┘");
	}
	if (state is State.PlayerHorizontal or State.PlayerVertical)
	{
		render.AppendLine();
		render.AppendLine("  It is your turn.");
		render.Append("  Press any key to aim your ○ dart... ");
	}
	if (state is State.ComputerHorizontal or State.ComputerVertical)
	{
		render.AppendLine();
		render.Append("  Computer's turn. Wait for it to throw it's ● dart.");
	}
	if (state is State.ConfirmRandomTurnOrder)
	{
		render.AppendLine();
		render.AppendLine("  You and the computer flip a coin and decide that ");
		render.AppendLine($"  {(playerGoesFirst ? "you" : "the computer")} will go first.");
		render.AppendLine();
		render.Append("  Press [enter] to continue...");
	}
	if (state is State.ConfirmPlayerThrow)
	{
		render.AppendLine();
		render.AppendLine("  You threw a dart.");
		if (darts[^1].Position is null)
		{
			render.AppendLine();
			render.AppendLine("  Dart collision! Both darts fell off the board.");
		}
		render.AppendLine();
		render.Append("  Press [enter] to continue...");
	}
	if (state is State.ConfirmComputerThrow)
	{
		render.AppendLine();
		render.AppendLine("  Computer threw a dart.");
		if (darts[^1].Position is null)
		{
			render.AppendLine();
			render.AppendLine("  Dart collision! Both darts fell off the board.");
		}
		render.AppendLine();
		render.Append("  Press [enter] to continue...");
	}
	if (state is State.ConfirmGameEnd)
	{
		var (playerScore, computerScore) = CalculateScores();
		render.AppendLine();
		render.AppendLine("  Game Complete! Final Scores...");
		render.AppendLine($"  Your Score: {playerScore}");
		render.AppendLine($"  Computer's Score: {computerScore}");
		render.AppendLine();
		if (playerScore > computerScore)
		{
			render.AppendLine("  You Win!");
		}
		else if (playerScore < computerScore)
		{
			render.AppendLine("  You Lose!");
		}
		else
		{
			render.AppendLine("  Draw!");
		}
		render.AppendLine();
		render.Append("  Press [enter] to return to the main screen...");
	}

	Console.CursorVisible = false;
	Console.SetCursorPosition(0, 0);
	Console.Write(render);
}

(int PlayerScore, int ComputerScore) CalculateScores()
{
	string[] scoreBoard =
	[
		"111111112222222233333332222222211111111",
		"111111112222222233333332222222211111111",
		"111111112222222233333332222222211111111",
		"111111162222225553333355522222261111111",
		"222222223333333344444443333333322222222",
		"222222223333333344444443333333322222222",
		"222222223333333344444443333333322222222",
		"222222223333333344494443333333322222222",
		"222222223333333344444443333333322222222",
		"222222223333333344444443333333322222222",
		"222222223333333344444443333333322222222",
		"111111162222225553333355522222261111111",
		"111111112222222233333332222222211111111",
		"111111112222222233333332222222211111111",
		"111111112222222233333332222222211111111",
	];

	int playerScore = 0;
	int computerScore = 0;

	foreach (var dart in darts)
	{
		if (dart.Position.HasValue)
		{
			if (dart.Player)
			{
				playerScore += scoreBoard[dart.Position.Value.Y][dart.Position.Value.X] - '0';
			}
			else
			{
				computerScore += scoreBoard[dart.Position.Value.Y][dart.Position.Value.X] - '0';
			}
		}
	}

	return (playerScore, computerScore);
}

enum State
{
	Main,
	ConfirmRandomTurnOrder,
	PlayerHorizontal,
	PlayerVertical,
	ConfirmPlayerThrow,
	ComputerHorizontal,
	ComputerVertical,
	ConfirmComputerThrow,
	ConfirmGameEnd,
}