SinMaiLauncher/TextAnimation.cs

using System.Text;

namespace SinMaiLauncher
{
    public static class TextAnimation
    {
        public static IEnumerable<string> LoadingTextSeq(int len)
        {
            IReadOnlyCollection<char> sym = ['甲', '申', '由', '申'];
            const char padding = '.';

            var symEnu = Loop(sym).GetEnumerator();

            while (true)
            {
                var sb = new StringBuilder();

                for (int i = 0; i < len; i++)
                {
                    symEnu.MoveNext();
                    sb.Clear();

                    sb.Append(symEnu.Current);
                    for (int j = 0; j < i; j++) sb.Append(padding);

                    yield return sb.ToString();
                }
            }
        }

        private static IEnumerable<T> Loop<T>(IEnumerable<T> source)
        {
            while (true)
            {
                foreach (var item in source)
                {
                    yield return item;
                }
            }
        }
    }
}