BrainFuck interpreter in C#

BrainFrack

using System;
namespace BrainFrack
{
    class Program
    {
        static unsafe void Main(string[] args)
        {
            int size = 30000;
            byte* ptr = (byte*)System.Runtime.InteropServices.Marshal.AllocCoTaskMem(size);
            for (int i = 0; i < size; i++) *ptr++ = 0;
            ptr -= size;
            string code = Console.ReadLine();
            Console.Clear();
            run(code, ref ptr);
            Console.ReadLine();
        }
        static unsafe void run(string code, ref byte* ptr)
        {
            for (int i = 0; i < code.Length; i++)
                switch (code[i])
                {
                    case '>': ptr++; break;
                    case '<': ptr--; break;
                    case '+': (*ptr)++; break;
                    case '-': (*ptr)--; break;
                    case '.': Console.Write((char)*ptr); break;
                    case ',': *ptr = (byte)Console.ReadKey(true).KeyChar; break;
                    case '[':
                        run(code.Substring(i + 1), ref ptr);
                        while (code[++i] != ']') ; break;
                    case ']':
                        if (*ptr == 0) return;
                        i = -1; break;
                }
        }
    }
}