Unity editor script simple snake game

Snake.cs

using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

public class Snake : EditorWindow
{
	//Settings
	int unit = 25;
	Color headCol = new Color(0, 0.5f, 1);
	Color tailCol = new Color(0, 0.5f, 0.8f);
	Color foodCol = new Color(0, 1, 0.4f);
	float speed = 0.1f;

	//Private Vairables
	private bool first;
	private int score;
	private Vector2 gameSize;
	private Vector2 foodPos;
	private Vector2 head;
	private Vector2 startSize;
	private List<Vector2> tail;
	private Texture2D headTex;
	private Texture2D tailTex;
	private Texture2D foodTex;
	int dir = 4; //0=up, 1=right, 2=down, 3=left, 4=still
	private float lastTime;

	[MenuItem("Window/Snake")]
	static void Init()
	{
		EditorWindow win = EditorWindow.GetWindow(typeof(Snake));
		win.Show();
	}

	void Begining()
	{
		//Init game
		first = true;
		gameSize = new Vector2(Mathf.Round(Screen.width / unit), Mathf.Round(Screen.height / unit));
		head = new Vector2(Mathf.Round(gameSize.x / 2), Mathf.Round(gameSize.y / 2));
		tail = new List<Vector2>();
		tail.Add(head);

		//Get start size
		startSize = new Vector2(Screen.width, Screen.height);

		//Gen food
		foodPos = new Vector2(Mathf.Round(Random.Range(0, gameSize.x - 1)), Mathf.Round(Random.Range(0, gameSize.y - 1)));

		//Generate Textures
		headTex = new Texture2D(1, 1);
		headTex.filterMode = FilterMode.Point;
		headTex.SetPixel(0, 0, headCol);
		headTex.Apply();

		tailTex = new Texture2D(1, 1);
		tailTex.filterMode = FilterMode.Point;
		tailTex.SetPixel(0, 0, tailCol);
		tailTex.Apply();

		foodTex = new Texture2D(1, 1);
		foodTex.filterMode = FilterMode.Point;
		foodTex.SetPixel(0, 0, foodCol);
		foodTex.Apply();
	}

	void OnGUI()
	{
		if (!first) Begining();

		#region Input
		//WASD
		if (Event.current.keyCode == KeyCode.W) dir = 0;
		if (Event.current.keyCode == KeyCode.D) dir = 1;
		if (Event.current.keyCode == KeyCode.S) dir = 2;
		if (Event.current.keyCode == KeyCode.A) dir = 3;

		//ARROWS
		if (Event.current.keyCode == KeyCode.UpArrow) dir = 0;
		if (Event.current.keyCode == KeyCode.RightArrow) dir = 1;
		if (Event.current.keyCode == KeyCode.DownArrow) dir = 2;
		if (Event.current.keyCode == KeyCode.LeftArrow) dir = 3;
		#endregion

		if (EditorApplication.timeSinceStartup - lastTime > speed)
		{
			lastTime = (float) EditorApplication.timeSinceStartup;

			#region Movement
			if (dir == 0)
			{
				head = new Vector2(head.x, head.y - 1);
			}
			else if (dir == 1)
			{
				head = new Vector2(head.x + 1, head.y);
			}
			else if (dir == 2)
			{
				head = new Vector2(head.x, head.y + 1);
			}
			else if (dir == 3)
			{
				head = new Vector2(head.x - 1, head.y);
			}
			#endregion

			//Check collision with sides
			if (head.x < 0 || head.x > gameSize.x) Die();
			if (head.y < 0 || head.y > gameSize.y) Die();

			//Check collision with self
			for (int i = 0; i < tail.Count; i++)
			{
				if (tail[i] == head && i != 0)
					Die();
			}

			//Check food collision
			if (head == foodPos) Eat();

			//Shift tail
			tail.RemoveAt(tail.Count - 1);
			tail.Insert(0, head);

			//Check updated size
			if (startSize != new Vector2(Screen.width, Screen.height)) Die();
		}

		//Draw
		///Food
		GUI.DrawTexture(new Rect(foodPos.x * unit, foodPos.y * unit, unit, unit), foodTex);

		///Food count
		EditorGUI.LabelField(new Rect(Screen.width / 2, 20, 20, 20), score.ToString());

		///Tail
		foreach (Vector2 vec in tail)
			GUI.DrawTexture(new Rect(vec.x * unit, vec.y * unit, unit, unit), tailTex);

		///Head
		GUI.DrawTexture(new Rect(head.x * unit, head.y * unit, unit, unit), headTex);

		//Update
		this.Repaint();
	}

	void Die()
	{
		gameSize = new Vector2(Screen.width / unit, Screen.height / unit);
		startSize = new Vector2(Screen.width, Screen.height);
		score = 0;
		head = new Vector2(Mathf.Round(gameSize.x / 2), Mathf.Round(gameSize.y / 2));
		tail = new List<Vector2>();
		tail.Add(head);
		dir = 4;

		//Gen food
		foodPos = new Vector2(Mathf.Round(Random.Range(0, gameSize.x - 1)), Mathf.Round(Random.Range(0, gameSize.y - 1)));
	}

	void Eat()
	{
		tail.Insert(tail.Count - 1, tail[tail.Count - 1]);
		score++;

		//Gen food
		foodPos = new Vector2(Mathf.Round(Random.Range(0, gameSize.x - 1)), Mathf.Round(Random.Range(0, gameSize.y - 1)));
	}
}